Patent Publication Number: US-2023161613-A1

Title: Enabling a host passthrough based on a hardware identification instruction

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure pertains to the field of data processing, and more particularly, to the field of virtualizing resources in data processing systems. 
     2. Background Art 
     Generally, the concept of virtualization of resources in data processing systems allows multiple instances of one or more operating systems (each, an “OS”) to run on a single data processing system, even though each OS is designed to have complete, direct control over the system and its resources. Virtualization is typically implemented by using software (e.g., a virtual machine monitor, or a “VMM”) to present to each OS a “virtual machine” (a “VM”) having virtual resources that the OS completely and directly controls, while the VMM maintains a system environment for implementing virtualization policies such as sharing and/or allocating the physical resources among the VMs (the “virtualization environment”). Each OS, and any other software, that runs on a VM, unaware of the virtualization environment, is referred to as a “guest” or as “guest software,” while a “host” or “host software” is software, such as a VMM, that runs outside of, and is not necessarily completely aware of, the virtualization environment. 
     A processor in various data processing systems support virtualization, for example, by variously operating in either of two modes including a “root” mode in which software runs directly on the hardware, outside of any virtualization environment, and a “non-root” mode in which software runs at its intended privilege level, but within a virtualization environment hosted by a VMM running in root mode. In a virtualization environment, certain events, operations, and situations, such as external interrupts or attempts to access privileged registers or resources, are “intercepted,” i.e., cause the processor to exit the virtualization environment so that the VMM operates, for example, to implement virtualization policies. Such a processor supports instructions for establishing, entering, exiting, and maintaining a virtualization environment, and includes register bits or other structures that indicate or control virtualization capabilities of the processor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The various embodiments of the present invention are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which: 
         FIG.  1    shows a functional block diagram illustrating features of a virtualization architecture to conditionally perform a host passthrough according to an embodiment. 
         FIG.  2 A  shows a flow diagram illustrating features of a method to determine an availability of a host passthrough functionality to a virtual machine according to an embodiment. 
         FIG.  2 B  shows a flow diagram illustrating features of a method to enable a virtual machine to avail of a host passthrough according to an embodiment. 
         FIG.  3    shows a flow diagram illustrating features of a method to perform operations based on a hardware identification instruction of a virtual machine according to an embodiment. 
         FIG.  4    shows a functional block diagram illustrating features of a virtualization architecture to conditionally perform a host passthrough according to an embodiment. 
         FIG.  5    shows a functional block diagram illustrating features of a virtualization architecture to execute a hardware identification instruction with a virtual machine according to an embodiment. 
         FIG.  6    shows a functional block diagram illustrating features of a virtualization architecture to conditionally enable host passthroughs according to an embodiment. 
         FIGS.  7 A through  7 B  are block diagrams illustrating a generic vector friendly instruction format and instruction templates thereof according to embodiments of the invention. 
         FIGS.  8 A through  8 D  are block diagrams illustrating an exemplary specific vector friendly instruction format according to embodiments of the invention. 
         FIG.  9    is a block diagram of a register architecture according to one embodiment of the invention. 
         FIG.  10 A  is a block diagram illustrating both an exemplary in-order pipeline and an exemplary register renaming, out-of-order issue/execution pipeline according to embodiments of the invention. 
         FIG.  10 B  is a block diagram illustrating both an exemplary embodiment of an in-order architecture core and an exemplary register renaming, out-of-order issue/execution architecture core to be included in a processor according to embodiments of the invention. 
         FIGS.  11 A through  11 B  illustrate a block diagram of a more specific exemplary in-order core architecture, which core would be one of several logic blocks (including other cores of the same type and/or different types) in a chip. 
         FIG.  12    is a block diagram of a processor that may have more than one core, may have an integrated memory controller, and may have integrated graphics according to embodiments of the invention. 
         FIGS.  13  through  16    are block diagrams of exemplary computer architectures. 
         FIG.  17    is a block diagram contrasting the use of a software instruction converter to convert binary instructions in a source instruction set to binary instructions in a target instruction set according to embodiments of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments discussed herein variously provide techniques and mechanisms for a host passthrough to be conditionally performed based on a hardware identification instruction which is to be executed with a virtual machine. In the following description, numerous details are discussed to provide a more thorough explanation of the embodiments of the present disclosure. It will be apparent to one skilled in the art, however, that embodiments of the present disclosure may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form, rather than in detail, in order to avoid obscuring embodiments of the present disclosure. 
     Note that in the corresponding drawings of the embodiments, signals are represented with lines. Some lines may be thicker, to indicate a greater number of constituent signal paths, and/or have arrows at one or more ends, to indicate a direction of information flow. Such indications are not intended to be limiting. Rather, the lines are used in connection with one or more exemplary embodiments to facilitate easier understanding of a circuit or a logical unit. Any represented signal, as dictated by design needs or preferences, may actually comprise one or more signals that may travel in either direction and may be implemented with any suitable type of signal scheme. 
     Throughout the specification, and in the claims, the term “connected” means a direct connection, such as electrical, mechanical, or magnetic connection between the things that are connected, without any intermediary devices. The term “coupled” means a direct or indirect connection, such as a direct electrical, mechanical, or magnetic connection between the things that are connected or an indirect connection, through one or more passive or active intermediary devices. The term “circuit” or “module” may refer to one or more passive and/or active components that are arranged to cooperate with one another to provide a desired function. The term “signal” may refer to at least one current signal, voltage signal, magnetic signal, or data/clock signal. The meaning of “a,” “an,” and “the” include plural references. The meaning of “in” includes “in” and “on.” 
     The term “device” may generally refer to an apparatus according to the context of the usage of that term. For example, a device may refer to a stack of layers or structures, a single structure or layer, a connection of various structures having active and/or passive elements, etc. Generally, a device is a three-dimensional structure with a plane along the x-y direction and a height along the z direction of an x-y-z Cartesian coordinate system. The plane of the device may also be the plane of an apparatus which comprises the device. 
     The term “scaling” generally refers to converting a design (schematic and layout) from one process technology to another process technology and subsequently being reduced in layout area. The term “scaling” generally also refers to downsizing layout and devices within the same technology node. The term “scaling” may also refer to adjusting (e.g., slowing down or speeding up—i.e. scaling down, or scaling up respectively) of a signal frequency relative to another parameter, for example, power supply level. 
     The terms “substantially,” “close,” “approximately,” “near,” and “about,” generally refer to being within +/−10% of a target value. For example, unless otherwise specified in the explicit context of their use, the terms “substantially equal,” “about equal” and “approximately equal” mean that there is no more than incidental variation between among things so described. In the art, such variation is typically no more than +/−10% of a predetermined target value. 
     It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the invention described herein are, for example, capable of operation in other orientations than those illustrated or otherwise described herein. 
     Unless otherwise specified the use of the ordinal adjectives “first,” “second,” and “third,” etc., to describe a common object, merely indicate that different instances of like objects are being referred to and are not intended to imply that the objects so described must be in a given sequence, either temporally, spatially, in ranking or in any other manner. 
     The terms “left,” “right,” “front,” “back,” “top,” “bottom,” “over,” “under,” and the like in the description and in the claims, if any, are used for descriptive purposes and not necessarily for describing permanent relative positions. For example, the terms “over,” “under,” “front side,” “back side,” “top,” “bottom,” “over,” “under,” and “on” as used herein refer to a relative position of one component, structure, or material with respect to other referenced components, structures or materials within a device, where such physical relationships are noteworthy. These terms are employed herein for descriptive purposes only and predominantly within the context of a device z-axis and therefore may be relative to an orientation of a device. Hence, a first material “over” a second material in the context of a figure provided herein may also be “under” the second material if the device is oriented upside-down relative to the context of the figure provided. In the context of materials, one material disposed over or under another may be directly in contact or may have one or more intervening materials. Moreover, one material disposed between two materials may be directly in contact with the two layers or may have one or more intervening layers. In contrast, a first material “on” a second material is in direct contact with that second material. Similar distinctions are to be made in the context of component assemblies. 
     The term “between” may be employed in the context of the z-axis, x-axis or y-axis of a device. A material that is between two other materials may be in contact with one or both of those materials, or it may be separated from both of the other two materials by one or more intervening materials. A material “between” two other materials may therefore be in contact with either of the other two materials, or it may be coupled to the other two materials through an intervening material. A device that is between two other devices may be directly connected to one or both of those devices, or it may be separated from both of the other two devices by one or more intervening devices. 
     As used throughout this description, and in the claims, a list of items joined by the term “at least one of” or “one or more of” can mean any combination of the listed terms. For example, the phrase “at least one of A, B or C” can mean A; B; C; A and B; A and C; B and C; or A, B and C. It is pointed out that those elements of a figure having the same reference numbers (or names) as the elements of any other figure can operate or function in any manner similar to that described, but are not limited to such. 
     In addition, the various elements of combinatorial logic and sequential logic discussed in the present disclosure may pertain both to physical structures (such as AND gates, OR gates, or XOR gates), or to synthesized or otherwise optimized collections of devices implementing the logical structures that are Boolean equivalents of the logic under discussion. 
     The technologies described herein may be implemented in one or more electronic devices. Non-limiting examples of electronic devices that may utilize the technologies described herein include any kind of mobile device and/or stationary device, such as cameras, cell phones, computer terminals, desktop computers, electronic readers, facsimile machines, kiosks, laptop computers, netbook computers, notebook computers, internet devices, payment terminals, personal digital assistants, media players and/or recorders, servers (e.g., blade server, rack mount server, combinations thereof, etc.), set-top boxes, smart phones, tablet personal computers, ultra-mobile personal computers, wired telephones, combinations thereof, and the like. More generally, the technologies described herein may be employed in any of a variety of electronic devices including a processor which supports virtualization functionality. 
     As used herein, “virtual machine” (or “VM”) refers to a process which emulates physical hardware that, for example, is to run one or more programs, deploy apps and/or the like. In a typical scenario, one or more virtual “guest” machines run on a physical “host” machine—e.g., wherein some or all such one or more virtual machines each run its own operating system, and functions separately from any other VM. 
     As used herein, “hypervisor,” “virtual machine manager” (or “VMM”), and related terms variously refer to a process which emulates or otherwise presents a virtual machine, and which manages an execution of a guest OS with said virtual machine. 
     As used herein, “VM exit” refers to a switch—e.g., by physical processor hardware or a virtual processor—from a context for VM (guest) operations to a different context for VMM (host) operations. A VM exit is performed, for example, based on any of various privileged instruction, exceptions, interrupts, mode set register (MSR) reads etc. 
     In general, a VM exit includes or otherwise depends on processor logic saving a snapshot of a VM&#39;s state at the time of the VM exit. Such VM state is subsequently reacquired with the processor logic when, for example, the processor logic is to reenter the VM context. VM exits and reentries include or are otherwise associated with performance overhead—e.g., including saving guest state and controls, reloading host state/controls, saving later host state/controls, and reloading guest state/controls—which are often a source of significant performance degradation in a virtualized system. To mitigate such overhead, some embodiment variously provide hardware resources and/or software resources to enable a host passthrough based on an instruction which is to communicate information describing one or more hardware characteristics of a processor. 
       FIG.  1    illustrates features of a virtualization architecture  100  to conditionally perform a host passthrough according to an embodiment. Virtualization architecture  100  illustrates one example of an embodiment wherein a hardware platform supports functionality to execute a hardware identification instruction with a virtual machine (VM)—e.g., wherein such execution comprises or otherwise results in a conditional performance of a VM exit (or alternatively, foregoing said VM exit) based on whether a VM resource is authorized to avail of a host passthrough. 
     As shown in  FIG.  1   , virtualization architecture  100  comprises a bare platform hardware  110  (e.g., that of a personal computer, mainframe computer, portable computer, handheld device, set-top box, or any other suitable computing system) which includes processor  120  and memory  130 . Hardware  110  comprises a data processing apparatus capable of executing any of various suitable OSes and/or VMM software. Processor  120  is, for example, any type of processor, including a general purpose microprocessor, such as a processor in the Core™, Xeon™, or other processor family from Intel Corporation, or another processor from another company, or a digital signal processor or microcontroller. Although  FIG.  1    shows only one such processor  120 , hardware  110  includes any number of processors, in various embodiments. Memory  130  is, for example, static or dynamic random-access memory, semiconductor-based read only or flash memory, magnetic or optical disk memory, any other type of medium readable by processor  120 , or any combination of such mediums. Hardware  110  also includes any number of input/output or other devices (not shown), in some embodiments. 
     In this embodiment, processor  120  supports execution of a hypervisor process, such as the illustrative virtual machine monitor (VMM)  140  shown. VMM  140  is a “root mode host” because it runs in root mode on processor  120 . VMM  140  comprises any of various suitable software, firmware, or hardware host installed to run on, or accessible to, hardware  110 , to present one or more virtual machines (VMs), i.e., abstractions of hardware  110 , to guests, or to otherwise create VMs, manage VMs, and implement virtualization policies within a virtualization environment supported by virtualization architecture  100 . In other embodiments, a root mode host is any suitable monitor, hypervisor, OS, or other software, firmware, or hardware capable of controlling hardware  110 . 
     A guest comprises any OS, any VMM, including another instance of VMM  140 , any hypervisor, or any application or other software. Each guest expects to access physical resources, such as processor and platform registers, memory, and input/output devices, of hardware  110 , according to the architecture of the processor and the platform presented in the VM.  FIG.  1    shows VMs  150 ,  160 ,  170 ,  180 , and  190 , with guest OS  152  and guest applications  154  and  155  installed to run on VM  150 , guest OS  162  and guest applications  164  and  165  installed to run on VM  160 , guest VMM  172  installed to run on VM  170 , guest OS  182  installed to run on VM  180 , and guest OS  192  installed to run on VM  190 . In this embodiment, all guests run in non-root mode. Although  FIG.  1    shows five VMs and nine guests, any number of VMs are created and any number of guests installed to run on each VM within the scope of the present invention. 
     Although some embodiments are not limited in this regard, virtualization architecture  100  is “layered” or “recursive” because, in this example, it allows one VMM (e.g., VMM  140 ) to host another hypervisor process, such as VMM  172 , as a guest. In other embodiments, VMM  140  does not provide for any such guest hypervisor process. In virtualization architecture  100 , VMM  140  is the host of the virtualization environment including VMs  150 ,  160  and  170 , and is not a guest in any virtualization environment because it is installed to run on hardware  110  with no “intervening” monitor between it and hardware  110 . An “intervening” monitor is a monitor, such as VMM  172 , that hosts a guest, such as guest OS  182 , but is also a guest itself. VMM  172  is the host of the virtualization environment including VMs  180  and  190 , but is also a guest in the virtualization environment hosted by VMM  140 . An intervening monitor (e.g., VMM  172 ) is referred to herein as a parent guest, because it functions as both a parent to another VM (or hierarchy of VMs) and as a guest of an underlying VMM (e.g., VMM  140  is a parent of VMM  172  which is a parent to guests  182  and  192 ). 
     A monitor, such as VMM  140 , is referred to as the “parent” of a guest, such as guest OSs  152 ,  162 , guest applications  154 ,  155 ,  164 ,  165 , and guest VMM  172 , if there are no intervening monitors between it and the guest. The guest is referred to as the “child” of that monitor. A guest is both a child and a parent, in some embodiments. For example, guest VMM  172  is a child of VMM  140  and the parent of guest OS  182  and guest OS  192 . 
     A resource that can be accessed by a guest is classified either as a “privileged” or a “non-privileged” resource. For a privileged resource, a host (e.g., VMM  140 ) facilitates the functionality desired by the guest while retaining ultimate control over the resource. Non-privileged resources do not need to be controlled by the host and are accessed directly by a guest. 
     Furthermore, each guest OS expects to handle various events such as exceptions (e.g., page faults, and general protection faults), interrupts (e.g., hardware interrupts and software interrupts), and platform events (e.g., initialization and system management interrupts). These exceptions, interrupts, and platform events are referred to collectively and individually as “events” herein. Some of these events are “privileged” because they are to be handled by a host to ensure proper operation of VMs, protection of the host from guests, and protection of guests from each other. 
     At a given time, processor  120  is executing instructions from VMM  140  or any guest, thus VMM  140  or the guest is active and running on, or in control of, processor  120 . When a privileged event occurs or a guest attempts to access a privileged resource, control is transferred from the guest to VMM  140 . The transfer of control from a guest to a host is referred to as a “VM exit” herein. After handling the event or facilitating the access to the resource appropriately, VMM  140  returns control to a guest. The transfer of control from a host to a guest is referred to as a “VM entry” herein. 
     In the embodiment of  FIG.  1   , processor  120  controls the operation of VMs according to data stored in virtual machine control structure (“VMCS”)  132 . VMCS  132  is a structure that contains state of a guest or guests, state of VMM  140 , execution control information indicating how VMM  140  is to control operation of a guest or guests, information regarding VM exits and VM entries, any other such information. Processor  120  reads information from VMCS  132  to determine the execution environment of a VM and constrain its behavior. In this embodiment, VMCS  132  is stored in memory  130 . In an embodiment, VMCS  132  is divided into multiple structures, each corresponding to a respective one host or one guest, where (for example) each such structure considered an independent VMCS. 
     The “guest hierarchy” of a VMM is the stack of software installed to run within the virtualization environment or environments supported by the VMM. Some embodiments comprise and/or facilitate operation of a virtualization architecture in which guest hierarchies include chains of pointers between VMCSs. These pointers are referred to as “parent pointers” when pointing from the VMCS of a child to the VMCS of a parent, and as “child pointers” when pointing from the VMCS of a parent to the VMCS of a child. 
     In an embodiment, processor  120  includes control logic  121  to support virtualization, including virtualization event processing in a virtualization architecture. Control logic  121  is implemented, for example, in microcode, programmable logic, hard-coded logic, or any other form of control logic within processor  120 . In other embodiments, control logic  121  is implemented in any form of hardware, software, or firmware, such as a processor abstraction layer, within a processor or within any device accessible or medium readable by a processor, such as memory  130 . 
     To facilitate execution of one or more processes of virtualization architecture  100 , processor  120  comprises a decoder  125  to decode one or more instructions, and an execution pipeline  127  to variously execute the decoded one or more instructions. In an embodiment, processor  120  provides an instruction set architecture (ISA) to accommodate such execution—e.g., wherein the ISA includes a hardware identification instruction. As used herein, “hardware identification instruction” refers to an instruction which, when executed, is to retrieve information which identifies any of various hardware characteristics of processor  120 . In this particular context, “hardware characteristic” refers to a characteristic of circuitry and/or other hardware, wherein said characteristic is independent of (and, for example, persists regardless of) a given state of software execution with said hardware. 
     By way of illustration and not limitation, a hardware identification instruction is to be executed to identify a manufacturer ID string, a stepping level, a model, a family, a thread, core, cache topology, and/or other such characteristics of a processor. In one such embodiment, a hardware identification instruction comprises a central processor unit identification (CPUID) instruction of an Intel x86 ISA—e.g., wherein the instruction is to retrieve information such as that which is accessible, for example, using the EAX, EBX, ECX, EDX registers of an Intel x86 architecture. 
     In existing technologies, the execution of a hardware identification instruction with a VM is, or otherwise includes, a privileged event which requires a VM exit to facilitate secure communication of hardware characteristic information to the VM using a hypervisor process. Some embodiments improve upon these existing technologies by modifying, extending or otherwise providing a host passthrough functionality which avoids the need for such a VM exit. 
     For example, control logic  121  (or other suitable logic of processor  120 ) is operable to advertise or otherwise identify to a hypervisor processes—such as VMM  140 , or guest VMM  172 —that a passthrough functionality is available for use based on a hardware identification instruction. Based on such identification, VMM  140  (or other such hypervisor process) makes a determination as to whether a given resource of a VM—e.g., the VM itself, a virtual processor of the VM, a process executed with the VM, or the like—is to be authorized to avail of said passthrough functionality. 
     Based on the determination, VMM  140  signals hardware of processor  120  to store configuration state information which specifies or otherwise indicates whether a particular one of a VM exit or a host passthrough is to be performed for a hardware identification instruction (if any) which is to be executed with the VM. By way of illustration and not limitation, configuration state information (CSI)  134  is stored to VMCS  132  and/or any of various other suitable repositories which are available to VMM  140  (and, for example, available to a VM which is provided with VMM  140 ). In an embodiment, CSI  134  comprises one or more configuration values which each correspond to a different respective one or more VMs. The one or more configuration values each identify whether the corresponding one or more VMS are to avail of host passthrough functionality for the execution of hardware identification instructions. 
     For example, control logic  121  and/or other suitable circuitry of processor  120  causes or otherwise facilitates the performance of one or more methods—e.g., wherein different embodiments variously include, are based on, and/or enable (at least in part) some or all such one or more methods. In the embodiment shown, control logic  121  comprises event logic  122  which is operable to recognize that an instruction, which is to be (or has been) decoded by decoder  125 , is a hardware identification instruction of a VM. In one such embodiment, evaluation logic  123  of control logic  121  determines, based on CSI  134 , whether execution of such a hardware identification instruction is to include or otherwise result in a VM exit (or alternatively, is to result in a host passthrough). 
     For example, where CSI  134  indicates that a VM resource is authorized to avail of a host passthrough functionality, execution pipeline  127  operates with passthrough logic  126  to communicate hardware characteristics to the VM without the need for a VM exit. Passthrough logic  126  provides functionality to pass low-level hardware information through to a VM without requiring an exit from a flow of the VM to a flow of a hypervisor which provides said VM. In an embodiment, some or all functionality of passthrough logic  126  is adapted from conventional host passthrough techniques and/or methods (which are not detailed herein to avoid obscuring certain features of various embodiments). 
     By contrast, where CSI  134  indicates that the VM resource is not authorized to avail of the host passthrough functionality, execution pipeline  127  instead operates with exit logic  124  to exit processor  120  from a flow of the VM, so that hardware characteristics can be communicated to the VM using VMM  140 . Exit logic  124  provides functionality to exit from a VM or other such guest—e.g., wherein exit logic  124  is to transition processor  120  from performing operations of a guest to performing operations of a host for that guest. In an embodiment, some or all functionality of exit logic  124  is adapted from conventional VM exit techniques and/or methods (which are not detailed herein to avoid obscuring certain features of various embodiments). In an alternative embodiment, execution pipeline  127  includes exit logic  124  and/or passthrough logic  126 . 
       FIG.  2 A  illustrates features of a method  200  to determine an availability of a host passthrough functionality according to an embodiment. Method  200  illustrates one example of an embodiment wherein a host processor advertises an ability to support a conditional host passthrough for a hardware identification instruction which is executed with a VM. Operations such as those of method  200  are performed, for example, with control logic  121  and/or other suitable circuitry of processor  120 . 
     As shown in  FIG.  2 A , method  200  comprises (at  210 ) identifying to a hypervisor process an availability of a control parameter which is to control access to a host passthrough functionality of the processor. For example, the identifying at  210  comprises control logic  121  (or other suitable circuitry of processor  120 ) signaling to VMM  140  capability information which identifies an ability to support a host passthrough functionality for a hardware identification instruction of a VM. In an embodiment, the identifying at  210  takes place while method  200  (or alternatively, operations performed concurrently with method  200 ) executes the hypervisor process. 
     The control parameter is identified at  210  as being available to be associated with one or more VMs, where such association is to determine (at least in part) whether an execution of an instruction, the execution by a given one such VM, is to result in an exit from a running of the VM. For example, the control parameter is to provide a basis for determining whether execution of the instruction is to result in a switch by the processor from a flow of that VM to a flow of the hypervisor process. In an embodiment, execution of the instruction is to identify to the VM a hardware characteristic of the processor—e.g., wherein the instruction is a CPUID instruction of an Intel x86 instruction set. 
     Referring now to  FIG.  2 B , method  250  illustrates a process—e.g., executed at least in part with software—which enables a hypervisor process to avail of a host passthrough according to an embodiment. Method  250  illustrates one example of an embodiment wherein a hypervisor process generates configuration state information to control which one of a host passthrough or a VM exit is to be performed based on an execution of a hardware identification instruction with a VM. Operations such as those of method  250  are performed, for example, with VMM  140  or guest VMM  172 —e.g., wherein method  250  is performed with (or alternatively, is part of) method  200 . 
     As shown in  FIG.  2 B , method  250  comprises (at  260 ) detecting an availability of a control parameter such as that which is advertised or otherwise identified by circuitry of a processor at  210 . For example, the control parameter is made available to the hypervisor process for use in determining whether an execution of a hardware identification instruction—the execution by a VM—is to result in a switch by the processor from a flow of the VM to a flow of a hypervisor process. In one such embodiment, method  250  (or alternatively, software operations of another method) also provides the VM, which is to execute a host operating system. 
     Based on the availability which is detected at  260 , method  250  (at  262 ) makes a determination of whether a resource of the VM is to be authorized to avail of a host passthrough functionality of the processor. For example, the VM resource is the VM itself, or a particular one or more virtual components (e.g., a virtual processor) of the VM, or a process which is to be executed with the VM. By way of illustration and not limitation, such a process comprises a guest OS, or software which is to run on that guest OS. 
     In an embodiment, the hypervisor process includes or is otherwise able to access reference information which specifies or otherwise indicates a basis on which the determination at  262  is to be made. For example, such reference information indicates an ability of the VM resource to support one or more operations which are to be performed conditionally to facilitate the execution of a hardware identification instruction. Additionally or alternatively, the reference information indicates (e.g., with a credential, a security capability, an integrity metric, or the like) a level of security which is associated with the VM resource. Additionally or alternatively, the reference information indicates a metric of operational efficiency of the VM resource. In some embodiments, the reference information additionally or alternatively comprises an explicit authorization of the VM resource—e.g., wherein the explicit authorization is provided by a manufacturer, system administrator, software developer or other such agent. 
     Based on such reference information (and, for example, a predefined criteria for evaluating said reference information) the hypervisor process makes the determination at  262 . It is noted that some embodiments are not limited with respect to a particular basis on which, or means by which, such reference information is generated, made available to, and/or evaluated by the hypervisor process. 
     Method  250  further comprises (at  264 ) signaling the processor to set the control parameter to a value based on the determination. For example, referring again to  FIG.  2 A , method  200  further comprises (at  212 ) processor circuitry receiving from the hypervisor process an indication of whether a resource of the VM is authorized to avail of the host passthrough functionality of the processor. At  214 , method  200  writes—to a repository of the control parameter—a value which is based on the indication. For example, the writing at  214  comprises circuitry of processor  120  writing CSI  134  to VMCS  132  (and/or to any of various other suitable memory resources of hardware  110 ). 
       FIG.  3    illustrates features of a method  300  to perform operations based on a hardware identification instruction of a virtual machine according to an embodiment. Method  300  illustrates one example of an embodiment wherein an execution of a hardware identification instruction—e.g., the execution with a guest OS or other suitable process of a VM—conditionally results in one of a host passthrough or a VM exit being performed. Operations such as those of method  300  are performed with one of VMs  150 ,  160 ,  170  (for example)—e.g., wherein method  300  includes, is performed with or is otherwise based on one or both od methods  200 ,  250 . 
     As shown in  FIG.  3   , method  300  comprises (at  310 ) detecting an instruction which is to be executed with a VM, wherein the execution of the instruction is to identify to the VM a hardware characteristic of a processor. For example, the instruction is a CPUID instruction of an Intel x86 instruction set, or any of various other suitable hardware identification instructions. In an embodiment, the VM is provided with (e.g., including managed by) a hypervisor process, wherein the circuitry of the processor is to execute the hypervisor process. In one such embodiment, the hypervisor process is a guest hypervisor process, which is provided with a host hypervisor process that is also to be executed with such processor circuitry. 
     Method  300  further comprises (at  312 ) accessing a control parameter—the accessing based on the instruction detected at  310 —which corresponds to a resource of the VM (or “VM resource”). In an embodiment, the control parameter (e.g., such as one which is set to a particular value at  214  of method  200 ) indicates whether the VM resource is authorized to avail of a host passthrough functionality of the processor. 
     Method  300  further comprises (at  314 ) determining, based on the control parameter, whether an execution of the instruction is to result in a switch by the processor from a flow of the VM to a flow of the hypervisor process. Although some embodiments are not limited in this regard, the determining at  314  comprises (for example) performing a search of a memory region which is shared by the VM and the hypervisor process. The search is to determine whether a shared table (or one or more other suitable data structures of the memory region) stores information which identifies the hardware characteristic. For example, such a shared memory region, in some embodiments, functions as a type of cache for information which is targeted by hardware identification instructions, and which (for example) was previously retrieved by an earlier hardware identification instruction. 
     In some embodiments, where it is indicated that the search of such a memory region has failed to find the targeted hardware characteristic information, the determining at  314  further determines, based on the control parameter, whether the VM resource is authorized to avail of the host passthrough functionality. In one such embodiment, where a failure of the search is indicated, and where the VM resource is authorized to avail of the host passthrough functionality, method  300  further signals the processor to communicate the hardware characteristic information to the VM via a host passthrough. Based on such signaling, the execution of the instruction (in some embodiments) results in the hardware characteristic information being stored to the memory region—e.g., in addition to the hardware characteristic information being provided to the VM as a result of such execution. 
     In another such embodiment, where the failure of the search is indicated, and where the VM resource is unauthorized to avail of the host passthrough functionality, method  300  instead further signals the processor to initiate the switch from the flow of the VM to the flow of the hypervisor process. 
     Alternatively, in some embodiments, where successful search of such a shared memory region is indicated, method  300  provides a result of the execution based on an access of the hardware characteristic information in the memory region—e.g., wherein the hardware characteristic information is provided to the VM independent of any need to perform either a host passthrough or a VM exit. In still another embodiment, the determining at  314  is performed independent of a search (if any) of such a shared memory region based on the instruction detected at  310 . 
     In some embodiments, the control parameter which is accessed at  312  is further used by another VM (i.e., other than the VM performing method  300 ) to determine whether an execution of another hardware identification instruction, by that other VM, is to result in a switch by the processor from a flow of that other VM. 
     Additionally or alternatively, method  300  further comprises operations (not shown), similar to those in  FIG.  3   , which are variously performed each for a different respective one or more other VMs. By way of illustration and not limitation, such additional operations comprise detecting a second hardware identification instruction to be executed with a second VM. The second VM is to be provided with the hypervisor process or, for example, with another hypervisor process which is also to be executed with the same processor circuitry. Based on the second hardware identification instruction, method  300  further accesses a second control parameter which corresponds to a resource of that second VM. In an embodiment, this second control parameter similarly indicates whether the resource of the second VM (or “second VM resource”) is authorized to avail of the host passthrough functionality. For example, the second control parameter—like the control parameter accessed at  312 —is made available and set by operations such as those of methods  200 ,  250 . In one such embodiment, based on the second control parameter, additional operations of method  300  determine whether an execution of the second hardware identification instruction is to result in a second switch by the processor from a flow of the second VM to the flow of the hypervisor process. 
       FIG.  4    illustrates features of a virtualization architecture  400  to conditionally perform a host passthrough according to an embodiment. Virtualization architecture  400  illustrates one example of an embodiment which is to execute a hardware identification instruction, resulting in a performance of a selected one of a host passthrough or a VM exit. The selection is according to whether a VM resource is authorized to avail of a host passthrough functionality. In various embodiments, virtualization architecture  400  provides functionality such as that of virtualization architecture  100 . 
     As shown in  FIG.  4   , virtualization architecture  400  comprises hardware  410  to execute a host OS  412  which is to provide a VMM  420  (or any other suitable hypervisor process). In turn, VMM  420  is to facilitate hardware emulation with one or more VMs including, for example, the illustrative VM  430  shown. VM  430  is to execute a guest OS  440  and, in some embodiments, one or more applications (not shown) which are to run on guest OS  440 . 
     At a given time during operation of virtualization architecture  400 , a state of VMM  420  comprises a VMCS  421 , a VM exit handler  423 , a CPUID handler  424 , and a VM entry handler  425 . Furthermore, a state of VM  430  comprises a detector  441 , and a selector  442 —e.g., wherein the respective states of VMM  420  and VM  430  are variously maintained at memory  130 . In one such embodiment, hardware  410 , VMM  420 , and VM  430 , correspond functionally to hardware  110 , VMM  140 , and VM  150  (respectively)—e.g., wherein guest OS  440  and VMCS  421  provide functionality of guest OS  152  and VMCS  132  (respectively). In an embodiment, VMCS  421 , VM exit handler  423 , CPUID handler  424 , and VM entry handler  425  are implemented each with a respective sub-routine, method call, handler, and/or other suitable resource of VMM  420 —e.g., wherein detector  441 , and selector  442  are similarly implemented each with a respective resource of VM  430 . 
     In various embodiments, some or all of method  200  is performed with a processor (not shown) of hardware  410 —e.g., wherein methods  250 ,  300  are performed VMM  420 , and VM  430  (respectively). By way of illustration and not limitation, detector  441  provides functionality to perform a detection (such as that at  310  of method  300 ) of a CPUID instruction which is to be executed on behalf of guest OS  440 . Based on the detected instruction, detector  441  signals selector  442  to access a control parameter (e.g., represented by the illustrative configuration bit  443  shown), such as that which is set to a particular value at  214  of method  200 . In the embodiment shown, configuration bit  443  is written or otherwise made available to VM  430  by VMCS  421 . 
     In the case where VMCS  421  indicates that a resource of VM  430  is authorized to avail of a host passthrough functionality, selector  442  participates in a host passthrough  422  whereby hardware characteristic information is communicated to selector  442  (or another suitable resource of VM  430 ) without the need for processor circuitry to exit from running VM  430 . Such hardware characteristic information is communicated (e.g., with signal  444 ) to a consumer  445  of the information—for example, wherein consumer  445  is an applet, (sub)routine, script or other executing software which includes or otherwise operates based on the CPUID instruction. 
     By contrast, in an alternative case where VMCS  421  indicates that the resource of VM  430  is not authorized to avail of the host passthrough functionality, selector  442  instead generates a signal  449  to cause a VM exit, wherein hardware  410  switches from running VM  430  to running VMM  420 . In an embodiment, signal  449  causes VM exit handler  423  to implement such a VM exit—e.g., wherein VM exit handler  423  causes state of VM  430  to be saved to a memory of hardware  410 , and causes other state of VMM  420  (e.g., including state of CPUID handler  424  and VM entry handler  425 ) to be loaded for execution with the processor of hardware  410 . After the VM exit is completed, CPUID handler  424  retrieves hardware characteristic information describing the processor. Subsequently, VM entry handler  425  performs a VM entry to resume a running of VM  430 —e.g., so that the retrieved hardware characteristic information can be communicated (for example, with signal  426 ) to the consumer  445  of the information. 
       FIG.  5    illustrates features of a virtualization architecture  500  to execute a hardware identification instruction with a virtual machine according to another embodiment. Virtualization architecture  500  illustrates one example of an embodiment wherein the selective performance of one of a host passthrough or a VM exit is further conditioned upon whether information targeted by the hardware identification instruction is already in a memory region which is shared by a VM and a hypervisor process. In various embodiments, virtualization architecture  500  provides functionality such as that of virtualization architecture  100  or virtualization architecture  400 —e.g., wherein some or all of methods  200 ,  250 ,  300  are performed with virtualization architecture  500 . 
     As shown in  FIG.  5   , virtualization architecture  500  comprises hardware  510 , wherein a processor (not shown) thereof is to variously facilitate the execution of a host OS  512 , a VMM  520 , a VM  530 , and a guest OS  540 . In one such embodiment, hardware  510 , host OS  512 , VMM  520 , VM  530 , and guest OS  540  correspond functionally to hardware  410 , host OS  412 , VMM  420 , VM  430 , and guest OS  540  (respectively). 
     By way of illustration and not limitation, VMM  520  comprises or otherwise operates with a VMCS  521 , a VM exit handler  523 , a CPUID handler  524 , and a VM entry handler  525 —e.g., corresponding functionally to VMCS  421 , VM exit handler  423 , CPUID handler  424 , and VM entry handler  425  (respectively). Furthermore, VM  530  comprises or otherwise operates with a detector  541 , and a selector  542  which—for example—correspond functionally to detector  441 , and selector  442  (respectively). In one such embodiment, some or all of signals  526 ,  544 ,  549  are variously provided to a consumer  545  of hardware characteristic information based on respective CPUID instructions—e.g., wherein signals  526 ,  544 ,  549  correspond functionally to signals  426 ,  444 ,  449  (respectively). 
     In the example embodiment shown, VMM  520  and VM  530  each have access to a shared memory resource (such as the illustrative one or more shared memory tables  527  shown), wherein VM  530  further comprises an evaluator  546  to access the shared memory table(s)  527  based on a CPUID instruction which is to be executed with VM  530  on behalf of guest OS  540 . 
     In an illustrative scenario according to one embodiment, evaluator  546  provides additional functionality to search shared memory table(s)  527  for hardware characteristic information that is the target of a CPUID instruction detected by detector  541 . For example, shared memory table(s)  527  function as a type of cache for such hardware characteristic information. 
     Where the search of shared memory table(s)  527  is successful, evaluator  546  (or another suitable resource of VM  530 ) communicates the hardware characteristic information—e.g., with signal  547 —to consumer  545 . Otherwise, evaluator  546  signals selector  542  to perform operations—such as those of selector  442 —which determine (based on configuration bit  543 ) whether execution of the CPUID instruction is to result in host passthrough  522  or (alternatively) a VM exit. In a case where the hardware characteristic information is retrieved by VM  530  using host passthrough  522  (or, for example, using a VM exit), selector  542 —or another suitable resource of VM  530  or VMM  520 —further writes the hardware characteristic information to shared memory table(s)  527  using, for example, signal  548 . 
     Some embodiments facilitate a host passthrough based on a hardware identification instruction which is to be executed with a nested VM—i.e., a VM which is managed by or otherwise provided with a guest hypervisor process which, in turn, is provided with a host hypervisor process. For example, referring again to  FIG.  1   , in one illustrative embodiment, a control parameter corresponding to a resource of VM  180  is used to determine whether execution of a CPUID instruction on behalf of guest OS  182  is to include or otherwise result in a host passthrough or—alternatively—a switch by processor  120  from running VM  180  to running guest VMM  172 . In one such embodiment, VM  180  and guest VMM  172  correspond functionally to VM  530  and VMM  520  (respectively)—e.g., wherein a shared memory, accessible to both VM  180  and guest VMM  172 , is searched by VM  180  to determine whether hardware characteristic information, targeted by a CPUID instruction, is available to be retrieved without either a host passthrough or a VM exit. In some embodiments, such as shared memory additionally or alternatively stores information with which VM  180  is to identify a current value of the corresponding control parameter. 
       FIG.  6    illustrates features of a virtualization architecture  600  to conditionally enable various host passthroughs according to an embodiment. Virtualization architecture  600  illustrates one example of an embodiment wherein multiple VM resources—e.g., resources of different respective VMs—each correspond to a respective authorization state indicating whether a host passthrough functionality is to be made available for the execution of a hardware identification instruction. In various embodiments, virtualization architecture  600  provides functionality such as that of one of virtualization architectures  100 ,  400 ,  500 —e.g., wherein some or all of methods  200 ,  250 ,  300  are performed with virtualization architecture  600 . 
     As shown in  FIG.  6   , virtualization architecture  600  comprises a software environment which is provided with circuitry (not shown) such as those of hardware  110 , hardware  410 , or hardware  510 . In the example embodiment shown, the software environment includes a host domain  630 —comprising the illustrative VMM  632  shown—and a guest domain  620  which is managed by and/or otherwise provided with host domain  630 . VMM  632  is a hypervisor process to host one or more virtual machine processes (e.g., including the illustrative processes  622   a,    622   b,  . . . ,  622   n  shown). 
     A hardware processor (not shown) of virtualization architecture  600  variously executes instructions on behalf of host domain  630  and/or guest domain  620 . In one such embodiment, the processor supports a host passthrough functionality which is to be selectively made available to variously facilitate one or more VMs each executing a respective hardware identification instruction. 
     For example, control parameters are variously used to specify or otherwise indicate which of VM processes  622   a,    622   b,  . . . ,  622   n  are to have access to the host passthrough functionality. In the example embodiment shown, virtualization architecture  600  comprises one or more registers, tables, and/or other suitable storage resources (represented by the illustrative shared memory  610  shown) to function as a repository of said control parameters. 
     By way of illustration and not limitation, entries  612   a,    612   b,  . . . ,  612   n  in shared memory  610  variously identify configuration state of guest domain  620 —e.g., wherein entry  612   b  comprises configuration bits  624   a,    624   b,  . . . ,  624   n  which correspond to VM processes  622   a,    622   b,  . . . ,  622   n  (respectively). In the example embodiment shown, a value of configuration bit  624   a  indicates whether execution of a CPUID instruction (or other such hardware identification instruction) with process  622   a  is to comprise or otherwise result in the use of a host passthrough. Furthermore, a value of configuration bit  624   b  indicates whether execution of a CPUID instruction with process  622   b  is to result in use of such a host passthrough. Further still, a value of configuration bit  624   n  indicates whether execution of a CPUID instruction with process  622   n  is to result in use of such a host passthrough. In various embodiments, virtualization architecture  600  provides more, fewer and/or different control parameters to configure the availability of a host passthrough functionality. 
     Accordingly, in one such embodiment, some or all of control bits  624   a,    624 b, . . . ,  624   n  (or other such control parameters) selectively enables access to a host passthrough functionality, for hardware identification instructions, at a VM-specific granularity level. Additionally or alternatively, a given control parameter selectively enables such access at higher granularity level—e.g., wherein a given one of control bits  624   a,    624   b,  . . . ,  624   n  corresponds to multiple VM processes (such as VM processes which share a common host VMM), and identifies a single common authorization state for each of the multiple VM processes. 
     The figures described herein detail exemplary architectures and systems to implement embodiments of the above. In some embodiments, one or more hardware components and/or instructions described herein are emulated as detailed below, or implemented as software modules. 
     Embodiments of the instruction(s) detailed above are embodied may be embodied in a “generic vector friendly instruction format” which is detailed herein. In other embodiments, such a format is not utilized and another instruction format is used, however, the description herein of the writemask registers, various data transformations (swizzle, broadcast, etc.), addressing, etc. is generally applicable to the description of the embodiments of the instruction(s) above. Additionally, exemplary systems, architectures, and pipelines are detailed herein. Embodiments of the instruction(s) above may be executed on such systems, architectures, and pipelines, but are not limited to those detailed. 
     An instruction set may include one or more instruction formats. A given instruction format may define various fields (e.g., number of bits, location of bits) to specify, among other things, the operation to be performed (e.g., opcode) and the operand(s) on which that operation is to be performed and/or other data field(s) (e.g., mask). Some instruction formats are further broken down though the definition of instruction templates (or subformats). For example, the instruction templates of a given instruction format may be defined to have different subsets of the instruction format&#39;s fields (the included fields are typically in the same order, but at least some have different bit positions because there are less fields included) and/or defined to have a given field interpreted differently. Thus, each instruction of an ISA is expressed using a given instruction format (and, if defined, in a given one of the instruction templates of that instruction format) and includes fields for specifying the operation and the operands. For example, an exemplary ADD instruction has a specific opcode and an instruction format that includes an opcode field to specify that opcode and operand fields to select operands (sourcel/destination and source 2 ); and an occurrence of this ADD instruction in an instruction stream will have specific contents in the operand fields that select specific operands. A set of SIMD extensions referred to as the Advanced Vector Extensions (AVX) (AVX 1  and AVX 2 ) and using the Vector Extensions (VEX) coding scheme has been released and/or published (e.g., see Intel® 64 and IA-32 Architectures Software Developer&#39;s Manual, September 2014; and see Intel® Advanced Vector Extensions Programming Reference, October 2014). 
     Exemplary Instruction Formats 
     Embodiments of the instruction(s) described herein may be embodied in different formats. Additionally, exemplary systems, architectures, and pipelines are detailed herein. Embodiments of the instruction(s) may be executed on such systems, architectures, and pipelines, but are not limited to those detailed. 
     Generic Vector Friendly Instruction Format 
     A vector friendly instruction format is an instruction format that is suited for vector instructions (e.g., there are certain fields specific to vector operations). While embodiments are described in which both vector and scalar operations are supported through the vector friendly instruction format, alternative embodiments use only vector operations the vector friendly instruction format. 
       FIGS.  7 A through  7 B  are block diagrams illustrating a generic vector friendly instruction format and instruction templates thereof according to embodiments of the invention.  FIG.  7 A  is a block diagram illustrating a generic vector friendly instruction format and class A instruction templates thereof according to embodiments of the invention; while  FIG.  7 B  is a block diagram illustrating the generic vector friendly instruction format and class B instruction templates thereof according to embodiments of the invention. Specifically, a generic vector friendly instruction format  700  for which are defined class A and class B instruction templates, both of which include no memory access  705  instruction templates and memory access  720  instruction templates. The term generic in the context of the vector friendly instruction format refers to the instruction format not being tied to any specific instruction set. 
     While embodiments of the invention will be described in which the vector friendly instruction format supports the following: a 64 byte vector operand length (or size) with 32 bit (4 byte) or 64 bit (8 byte) data element widths (or sizes) (and thus, a 64 byte vector consists of either 16 doubleword-size elements or alternatively, 8 quadword-size elements); a 64 byte vector operand length (or size) with 16 bit (2 byte) or 8 bit (1 byte) data element widths (or sizes); a 32 byte vector operand length (or size) with 32 bit (4 byte), 64 bit (8 byte), 16 bit (2 byte), or 8 bit (1 byte) data element widths (or sizes); and a 16 byte vector operand length (or size) with 32 bit (4 byte), 64 bit (8 byte), 16 bit (2 byte), or 8 bit (1 byte) data element widths (or sizes); alternative embodiments may support more, less and/or different vector operand sizes (e.g., 256 byte vector operands) with more, less, or different data element widths (e.g., 128 bit (16 byte) data element widths). 
     The class A instruction templates in  FIG.  7 A  include:  1 ) within the no memory access  705  instruction templates there is shown a no memory access, full round control type operation  710  instruction template and a no memory access, data transform type operation  715  instruction template; and  2 ) within the memory access  720  instruction templates there is shown a memory access, temporal  725  instruction template and a memory access, non-temporal  730  instruction template. The class B instruction templates in  FIG.  7 B  include:  1 ) within the no memory access  705  instruction templates there is shown a no memory access, write mask control, partial round control type operation  712  instruction template and a no memory access, write mask control, vsize type operation  717  instruction template; and  2 ) within the memory access  720  instruction templates there is shown a memory access, write mask control  727  instruction template. 
     The generic vector friendly instruction format  700  includes the following fields listed herein in the order illustrated in  FIGS.  7 A through  7 B . 
     Format field  740 —a specific value (an instruction format identifier value) in this field uniquely identifies the vector friendly instruction format, and thus occurrences of instructions in the vector friendly instruction format in instruction streams. As such, this field is optional in the sense that it is not needed for an instruction set that has only the generic vector friendly instruction format. 
     Base operation field  742 —its content distinguishes different base operations. 
     Register index field  744 —its content, directly or through address generation, specifies the locations of the source and destination operands, be they in registers or in memory. These include a sufficient number of bits to select N registers from a P×Q (e.g. 32×512, 16×128, 32×1024, 64×1024) register file. While in one embodiment N may be up to three sources and one destination register, alternative embodiments may support more or less sources and destination registers (e.g., may support up to two sources where one of these sources also acts as the destination, may support up to three sources where one of these sources also acts as the destination, may support up to two sources and one destination). 
     Modifier field  746 —its content distinguishes occurrences of instructions in the generic vector instruction format that specify memory access from those that do not; that is, between no memory access  705  instruction templates and memory access  720  instruction templates (e.g., no memory access  746 A and memory access  746 B for the class field  768  respectively in  FIGS.  7 A-B ). Memory access operations read and/or write to the memory hierarchy (in some cases specifying the source and/or destination addresses using values in registers), while non-memory access operations do not (e.g., the source and destinations are registers). While in one embodiment this field also selects between three different ways to perform memory address calculations, alternative embodiments may support more, less, or different ways to perform memory address calculations. 
     Augmentation operation field  750 —its content distinguishes which one of a variety of different operations to be performed in addition to the base operation. This field is context specific. In one embodiment of the invention, this field is divided into a class field  768 , an alpha field  752 , and a beta field  754 . The augmentation operation field  750  allows common groups of operations to be performed in a single instruction rather than 2, 3, or 4 instructions. 
     Scale field  760 —its content allows for the scaling of the index field&#39;s content for memory address generation (e.g., for address generation that uses 2 scale*index+base). 
     Displacement Field  762 A—its content is used as part of memory address generation (e.g., for address generation that uses 2 scale*index+base+displacement). 
     Displacement Factor Field  762 B (note that the juxtaposition of displacement field  762 A directly over displacement factor field  762 B indicates one or the other is used)—its content is used as part of address generation; it specifies a displacement factor that is to be scaled by the size of a memory access (N)—where N is the number of bytes in the memory access (e.g., for address generation that uses 2 scale*index+base+scaled displacement). Redundant low-order bits are ignored and hence, the displacement factor field&#39;s content is multiplied by the memory operands total size (N) in order to generate the final displacement to be used in calculating an effective address. The value of N is determined by the processor hardware at runtime based on the full opcode field  774  (described later herein) and the data manipulation field  754 C. The displacement field  762 A and the displacement factor field  762 B are optional in the sense that they are not used for the no memory access  705  instruction templates and/or different embodiments may implement only one or none of the two. 
     Data element width field  764 —its content distinguishes which one of a number of data element widths is to be used (in some embodiments for all instructions; in other embodiments for only some of the instructions). This field is optional in the sense that it is not needed if only one data element width is supported and/or data element widths are supported using some aspect of the opcodes. 
     Write mask field  770 —its content controls, on a per data element position basis, whether that data element position in the destination vector operand reflects the result of the base operation and augmentation operation. Class A instruction templates support merging-writemasking, while class B instruction templates support both merging- and zeroing-writemasking. When merging, vector masks allow any set of elements in the destination to be protected from updates during the execution of any operation (specified by the base operation and the augmentation operation); in other one embodiment, preserving the old value of each element of the destination where the corresponding mask bit has a 0. In contrast, when zeroing vector masks allow any set of elements in the destination to be zeroed during the execution of any operation (specified by the base operation and the augmentation operation); in one embodiment, an element of the destination is set to  0  when the corresponding mask bit has a 0 value. A subset of this functionality is the ability to control the vector length of the operation being performed (that is, the span of elements being modified, from the first to the last one); however, it is not necessary that the elements that are modified be consecutive. Thus, the write mask field  770  allows for partial vector operations, including loads, stores, arithmetic, logical, etc. While embodiments of the invention are described in which the write mask field&#39;s  770  content selects one of a number of write mask registers that contains the write mask to be used (and thus the write mask field&#39;s  770  content indirectly identifies that masking to be performed), alternative embodiments instead or additional allow the write mask field&#39;s  770  content to directly specify the masking to be performed. 
     Immediate field  772 —its content allows for the specification of an immediate. This field is optional in the sense that is it not present in an implementation of the generic vector friendly format that does not support immediate and it is not present in instructions that do not use an immediate. 
     Class field  768 —its content distinguishes between different classes of instructions. With reference to  FIGS.  7 A-B , the contents of this field select between class A and class B instructions. In  FIGS.  7 A-B , rounded corner squares are used to indicate a specific value is present in a field (e.g., class A  768 A and class B  768 B for the class field  768  respectively in  FIGS.  7 A-B ). 
     Instruction Templates of Class A 
     In the case of the non-memory access  705  instruction templates of class A, the alpha field  752  is interpreted as an RS field  752 A, whose content distinguishes which one of the different augmentation operation types are to be performed (e.g., round  752 A. 1  and data transform  752 A. 2  are respectively specified for the no memory access, round type operation  710  and the no memory access, data transform type operation  715  instruction templates), while the beta field  754  distinguishes which of the operations of the specified type is to be performed. In the no memory access  705  instruction templates, the scale field  760 , the displacement field  762 A, and the displacement scale field  762 B are not present. 
     No-Memory Access Instruction Templates—Full Round Control Type Operation 
     In the no memory access full round control type operation  710  instruction template, the beta field  754  is interpreted as a round control field  754 A, whose content(s) provide static rounding. While in the described embodiments of the invention the round control field  754 A includes a suppress all floating point exceptions (SAE) field  756  and a round operation control field  758 , alternative embodiments may support may encode both these concepts into the same field or only have one or the other of these concepts/fields (e.g., may have only the round operation control field  758 ). 
     SAE field  756 —its content distinguishes whether or not to disable the exception event reporting; when the SAE field&#39;s  756  content indicates suppression is enabled, a given instruction does not report any kind of floating-point exception flag and does not raise any floating point exception handler. 
     Round operation control field  758 —its content distinguishes which one of a group of rounding operations to perform (e.g., Round-up, Round-down, Round-towards-zero and Round-to-nearest). Thus, the round operation control field  758  allows for the changing of the rounding mode on a per instruction basis. In one embodiment of the invention where a processor includes a control register for specifying rounding modes, the round operation control field&#39;s  758  content overrides that register value. 
     No Memory Access Instruction Templates—Data Transform Type Operation 
     In the no memory access data transform type operation  715  instruction template, the beta field  754  is interpreted as a data transform field  754 B, whose content distinguishes which one of a number of data transforms is to be performed (e.g., no data transform, swizzle, broadcast). 
     In the case of a memory access  720  instruction template of class A, the alpha field  752  is interpreted as an eviction hint field  752 B, whose content distinguishes which one of the eviction hints is to be used (in  FIG.  7 A , temporal  752 B. 1  and non-temporal  752 B. 2  are respectively specified for the memory access, temporal  725  instruction template and the memory access, non-temporal  730  instruction template), while the beta field  754  is interpreted as a data manipulation field  754 C, whose content distinguishes which one of a number of data manipulation operations (also known as primitives) is to be performed (e.g., no manipulation; broadcast; up conversion of a source; and down conversion of a destination). The memory access  720  instruction templates include the scale field  760 , and optionally the displacement field  762 A or the displacement scale field  762 B. 
     Vector memory instructions perform vector loads from and vector stores to memory, with conversion support. As with regular vector instructions, vector memory instructions transfer data from/to memory in a data element-wise fashion, with the elements that are actually transferred is dictated by the contents of the vector mask that is selected as the write mask. 
     Memory Access Instruction Templates—Temporal 
     Temporal data is data likely to be reused soon enough to benefit from caching. This is, however, a hint, and different processors may implement it in different ways, including ignoring the hint entirely. 
     Memory Access Instruction Templates—Non-Temporal 
     Non-temporal data is data unlikely to be reused soon enough to benefit from caching in the 1st-level cache and should be given priority for eviction. This is, however, a hint, and different processors may implement it in different ways, including ignoring the hint entirely. 
     Instruction Templates of Class B 
     In the case of the instruction templates of class B, the alpha field  752  is interpreted as a write mask control (Z) field  752 C, whose content distinguishes whether the write masking controlled by the write mask field  770  should be a merging or a zeroing. 
     In the case of the non-memory access  705  instruction templates of class B, part of the beta field  754  is interpreted as an RL field  757 A, whose content distinguishes which one of the different augmentation operation types are to be performed (e.g., round  757 A. 1  and vector length (VSIZE)  757 A. 2  are respectively specified for the no memory access, write mask control, partial round control type operation  712  instruction template and the no memory access, write mask control, VSIZE type operation  717  instruction template), while the rest of the beta field  754  distinguishes which of the operations of the specified type is to be performed. In the no memory access  705  instruction templates, the scale field  760 , the displacement field  762 A, and the displacement scale field  762 B are not present. 
     In the no memory access, write mask control, partial round control type operation  712  instruction template, the rest of the beta field  754  is interpreted as a round operation field  759 A and exception event reporting is disabled (a given instruction does not report any kind of floating-point exception flag and does not raise any floating point exception handler). 
     Round operation control field  759 A—just as round operation control field  758 , its content distinguishes which one of a group of rounding operations to perform (e.g., Round-up, Round-down, Round-towards-zero and Round-to-nearest). Thus, the round operation control field  759 A allows for the changing of the rounding mode on a per instruction basis. In one embodiment of the invention where a processor includes a control register for specifying rounding modes, the round operation control field&#39;s  758  content overrides that register value. 
     In the no memory access, write mask control, VSIZE type operation  717  instruction template, the rest of the beta field  754  is interpreted as a vector length field  759 B, whose content distinguishes which one of a number of data vector lengths is to be performed on (e.g., 128, 256, or 512 byte). 
     In the case of a memory access  720  instruction template of class B, part of the beta field  754  is interpreted as a broadcast field  757 B, whose content distinguishes whether or not the broadcast type data manipulation operation is to be performed, while the rest of the beta field  754  is interpreted the vector length field  759 B. The memory access  720  instruction templates include the scale field  760 , and optionally the displacement field  762 A or the displacement scale field  762 B. 
     With regard to the generic vector friendly instruction format  700 , a full opcode field  774  is shown including the format field  740 , the base operation field  742 , and the data element width field  764 . While one embodiment is shown where the full opcode field  774  includes all of these fields, the full opcode field  774  includes less than all of these fields in embodiments that do not support all of them. The full opcode field  774  provides the operation code (opcode). 
     The augmentation operation field  750 , the data element width field  764 , and the write mask field  770  allow these features to be specified on a per instruction basis in the generic vector friendly instruction format. 
     The combination of write mask field and data element width field create typed instructions in that they allow the mask to be applied based on different data element widths. 
     The various instruction templates found within class A and class B are beneficial in different situations. In some embodiments of the invention, different processors or different cores within a processor may support only class A, only class B, or both classes. For instance, a high performance general purpose out-of-order core intended for general-purpose computing may support only class B, a core intended primarily for graphics and/or scientific (throughput) computing may support only class A, and a core intended for both may support both (of course, a core that has some mix of templates and instructions from both classes but not all templates and instructions from both classes is within the purview of the invention). Also, a single processor may include multiple cores, all of which support the same class or in which different cores support different class. For instance, in a processor with separate graphics and general purpose cores, one of the graphics cores intended primarily for graphics and/or scientific computing may support only class A, while one or more of the general purpose cores may be high performance general purpose cores with out of order execution and register renaming intended for general-purpose computing that support only class B. Another processor that does not have a separate graphics core, may include one more general purpose in-order or out-of-order cores that support both class A and class B. Of course, features from one class may also be implement in the other class in different embodiments of the invention. Programs written in a high level language would be put (e.g., just in time compiled or statically compiled) into an variety of different executable forms, including: 1) a form having only instructions of the class(es) supported by the target processor for execution; or 2) a form having alternative routines written using different combinations of the instructions of all classes and having control flow code that selects the routines to execute based on the instructions supported by the processor which is currently executing the code. 
     Exemplary Specific Vector Friendly Instruction Format 
       FIG.  8    is a block diagram illustrating an exemplary specific vector friendly instruction format according to embodiments of the invention.  FIG.  8    shows a specific vector friendly instruction format  800  that is specific in the sense that it specifies the location, size, interpretation, and order of the fields, as well as values for some of those fields. The specific vector friendly instruction format  800  may be used to extend the x86 instruction set, and thus some of the fields are similar or the same as those used in the existing x86 instruction set and extension thereof (e.g., AVX). This format remains consistent with the prefix encoding field, real opcode byte field, MOD R/M field, SIB field, displacement field, and immediate fields of the existing x86 instruction set with extensions. The fields from  FIG.  7    into which the fields from  FIG.  8    map are illustrated. 
     It should be understood that, although embodiments of the invention are described with reference to the specific vector friendly instruction format  800  in the context of the generic vector friendly instruction format  700  for illustrative purposes, the invention is not limited to the specific vector friendly instruction format  800  except where claimed. For example, the generic vector friendly instruction format  700  contemplates a variety of possible sizes for the various fields, while the specific vector friendly instruction format  800  is shown as having fields of specific sizes. By way of specific example, while the data element width field  764  is illustrated as a one bit field in the specific vector friendly instruction format  800 , the invention is not so limited (that is, the generic vector friendly instruction format  700  contemplates other sizes of the data element width field  764 ). 
     The specific vector friendly instruction format  800  includes the following fields listed herein in the order illustrated in  FIG.  8 A . 
     EVEX Prefix (Bytes  0 - 3 )  802 —is encoded in a four-byte form. 
     Format Field  740  (EVEX Byte  0 , bits [ 7 : 0 ])—the first byte (EVEX Byte  0 ) is the format field  740  and it contains 0×62 (the unique value used for distinguishing the vector friendly instruction format in one embodiment of the invention). 
     The second-fourth bytes (EVEX Bytes  1 - 3 ) include a number of bit fields providing specific capability. 
     REX field  805  (EVEX Byte  1 , bits [ 7 - 5 ])—consists of a EVEX.R bit field (EVEX Byte  1 , bit [ 7 ]—R), EVEX.X bit field (EVEX byte  1 , bit [ 6 ]—X), and  757 BEX byte  1 , bit[ 5 ]-B). The EVEX.R, EVEX.X, and EVEX.B bit fields provide the same functionality as the corresponding VEX bit fields, and are encoded using is complement form, i.e. ZMMO is encoded as  1111 B, ZMM 15  is encoded as  0000 B. Other fields of the instructions encode the lower three bits of the register indexes as is known in the art (rrr, xxx, and bbb), so that Rrrr, Xxxx, and Bbbb may be formed by adding EVEX.R, EVEX.X, and EVEX.B. 
     REX′ field  810 —this is the first part of the REX′ field  810  and is the EVEX.R′ bit field (EVEX Byte  1 , bit [ 4 ]-R′) that is used to encode either the upper 16 or lower 16 of the extended 32 register set. In one embodiment of the invention, this bit, along with others as indicated herein, is stored in bit inverted format to distinguish (in the well-known x86 32-bit mode) from the BOUND instruction, whose real opcode byte is 62, but does not accept in the MOD R/M field (described herein) the value of 11 in the MOD field; alternative embodiments of the invention do not store this and the other indicated bits herein in the inverted format. A value of 1 is used to encode the lower 16 registers. In other words, R′Rrrr is formed by combining EVEX.R′, EVEX.R, and the other RRR from other fields. 
     Opcode map field  815  (EVEX byte  1 , bits [ 3 : 0 ]—mmmm)—its content encodes an implied leading opcode byte ( 0 F,  0 F  38 , or  0 F 3). 
     Data element width field  764  (EVEX byte  2 , bit [ 7 ]—W)—is represented by the notation EVEX.W. EVEX.W is used to define the granularity (size) of the datatype (either 32-bit data elements or 64-bit data elements). 
     EVEX.vvvv  820  (EVEX Byte  2 , bits [ 6 : 3 ]-vvvv)- the role of EVEX.vvvv may include the following: 1) EVEX.vvvv encodes the first source register operand, specified in inverted (1s complement) form and is valid for instructions with 2 or more source operands; 2) EVEX.vvvv encodes the destination register operand, specified in is complement form for certain vector shifts; or 3) EVEX.vvvv does not encode any operand, the field is reserved and should contain  1111   b.  Thus, EVEX.vvvv field  820  encodes the 4 low-order bits of the first source register specifier stored in inverted (1s complement) form. Depending on the instruction, an extra different EVEX bit field is used to extend the specifier size to 32 registers. 
     EVEX. 0   768  Class field (EVEX byte  2 , bit [ 2 ]-U)—If EVEX. 0  = 0 , it indicates class A or EVEX.UO; if EVEX. 0  = 1 , it indicates class B or EVEX.U 1 . 
     Prefix encoding field  825  (EVEX byte  2 , bits [ 1 : 0 ]-pp)—provides additional bits for the base operation field. In addition to providing support for the legacy SSE instructions in the EVEX prefix format, this also has the benefit of compacting the SIMD prefix (rather than requiring a byte to express the SIMD prefix, the EVEX prefix requires only 2 bits). In one embodiment, to support legacy SSE instructions that use a SIMD prefix ( 66 H, F 2 H, F 3 H) in both the legacy format and in the EVEX prefix format, these legacy SIMD prefixes are encoded into the SIMD prefix encoding field; and at runtime are expanded into the legacy SIMD prefix prior to being provided to the decoder&#39;s PLA (so the PLA can execute both the legacy and EVEX format of these legacy instructions without modification). Although newer instructions could use the EVEX prefix encoding field&#39;s content directly as an opcode extension, certain embodiments expand in a similar fashion for consistency but allow for different meanings to be specified by these legacy SIMD prefixes. An alternative embodiment may redesign the PLA to support the 2 bit SIMD prefix encodings, and thus not require the expansion. 
     Alpha field  752  (EVEX byte  3 , bit [ 7 ]—EH; also known as EVEX.EH, EVEX.rs, EVEX.RL, EVEX.write mask control, and EVEX.N; also illustrated with a)—as previously described, this field is context specific. 
     Beta field  754  (EVEX byte  3 , bits [ 6 : 4 ]-SSS, also known as EVEX.s 2 - 0 , EVEX.r 2 - 0 , EVEX.rr 1 , EVEX.LLO, EVEX.LLB; also illustrated with PP( 3 )—as previously described, this field is context specific. 
     REX′ field  810 —this is the remainder of the REX′ field and is the EVEX.V′ bit field (EVEX Byte  3 , bit [ 3 ]-V′) that may be used to encode either the upper 16 or lower 16 of the extended 32 register set. This bit is stored in bit inverted format. A value of 1 is used to encode the lower 16 registers. In other words, V′VVVV is formed by combining EVEX.V′, EVEX.vvvv. 
     Write mask field  770  (EVEX byte  3 , bits [ 2 : 0 ]-kkk)—its content specifies the index of a register in the write mask registers as previously described. In one embodiment of the invention, the specific value EVEX kkk=000 has a special behavior implying no write mask is used for the particular instruction (this may be implemented in a variety of ways including the use of a write mask hardwired to all ones or hardware that bypasses the masking hardware). 
     Real Opcode Field  830  (Byte  4 ) is also known as the opcode byte. Part of the opcode is specified in this field. 
     MOD R/M Field  840  (Byte  5 ) includes MOD field  842 , Reg field  844 , and R/M field  846 . As previously described, the MOD field&#39;s  842  content distinguishes between memory access and non-memory access operations. The role of Reg field  844  can be summarized to two situations: encoding either the destination register operand or a source register operand, or be treated as an opcode extension and not used to encode any instruction operand. The role of R/M field  846  may include the following: encoding the instruction operand that references a memory address, or encoding either the destination register operand or a source register operand. 
     Scale, Index, Base (SIB) Byte  850  (Byte  6 )—As previously described, the scale field&#39;s  760  content is used for memory address generation. SIB.SS  852 , SIB.xxx  854  and SIB.bbb  856 —the contents of these fields have been previously referred to with regard to the register indexes Xxxx and Bbbb. 
     Displacement field  762 A (Bytes  7 - 10 )—when MOD field  842  contains 10, bytes  7 - 10  are the displacement field  762 A, and it works the same as the legacy 32-bit displacement (disp 32 ) and works at byte granularity. 
     Displacement factor field  762 B (Byte  7 )—when MOD field  842  contains 01, byte  7  is the displacement factor field  762 B. The location of this field is that same as that of the legacy x86 instruction set  8 -bit displacement (disp 8 ), which works at byte granularity. Since disp 8  is sign extended, it can only address between −128 and 127 bytes offsets; in terms of 64 byte cache lines, disp 8  uses  8  bits that can be set to only four really useful values −128, −64, 0, and 64; since a greater range is often needed, disp 32  is used; however, disp 32  requires 4 bytes. In contrast to disp 8  and disp 32 , the displacement factor field  762 B is a reinterpretation of disp 8 ; when using displacement factor field  762 B, the actual displacement is determined by the content of the displacement factor field multiplied by the size of the memory operand access (N). This type of displacement is referred to as disp 8 *N. This reduces the average instruction length (a single byte of used for the displacement but with a much greater range). Such compressed displacement is based on the assumption that the effective displacement is multiple of the granularity of the memory access, and hence, the redundant low-order bits of the address offset do not need to be encoded. In other words, the displacement factor field  762 B substitutes the legacy x86 instruction set 8-bit displacement. Thus, the displacement factor field  762 B is encoded the same way as an x86 instruction set 8-bit displacement (so no changes in the ModRM/SIB encoding rules) with the only exception that disp 8  is overloaded to disp 8 *N. In other words, there are no changes in the encoding rules or encoding lengths but only in the interpretation of the displacement value by hardware (which needs to scale the displacement by the size of the memory operand to obtain a byte-wise address offset). Immediate field  772  operates as previously described. 
     Full Opcode Field 
       FIG.  8 B  is a block diagram illustrating the fields of the specific vector friendly instruction format  800  that make up the full opcode field  774  according to one embodiment of the invention. Specifically, the full opcode field  774  includes the format field  740 , the base operation field  742 , and the data element width (W) field  764 . The base operation field  742  includes the prefix encoding field  825 , the opcode map field  815 , and the real opcode field  830 . 
     Register Index Field 
       FIG.  8 C  is a block diagram illustrating the fields of the specific vector friendly instruction format  800  that make up the register index field  744  according to one embodiment of the invention. Specifically, the register index field  744  includes the REX field  805 , the REX′ field  810 , the MODR/M.reg field  844 , the MODR/M.r/m field  846 , the VVVV field  820 , xxx field  854 , and the bbb field  856 . 
     Augmentation Operation Field 
       FIG.  8 D  is a block diagram illustrating the fields of the specific vector friendly instruction format  800  that make up the augmentation operation field  750  according to one embodiment of the invention. When the class (U) field  768  contains  0 , it signifies EVEX.UO (class A  768 A); when it contains  1 , it signifies EVEX.U 1  (class B  768 B). When U=0 and the MOD field  842  contains  11  (signifying a no memory access operation), the alpha field  752  (EVEX byte  3 , bit [ 7 ]—EH) is interpreted as the rs field  752 A. When the rs field  752 A contains a  1  (round  752 A. 1 ), the beta field  754  (EVEX byte  3 , bits [ 6 : 4 ]-SSS) is interpreted as the round control field  754 A. The round control field  754 A includes a one bit SAE field  756  and a two bit round operation field  758 . When the rs field  752 A contains a  0  (data transform  752 A. 2 ), the beta field  754  (EVEX byte  3 , bits [ 6 : 4 ]-SSS) is interpreted as a three bit data transform field  754 B. When U= 0  and the MOD field  842  contains 00, 01, or 10 (signifying a memory access operation), the alpha field  752  (EVEX byte  3 , bit [ 7 ]—EH) is interpreted as the eviction hint (EH) field  752 B and the beta field  754  (EVEX byte  3 , bits [ 6 : 4 ]-SSS) is interpreted as a three bit data manipulation field  754 C. 
     When U= 1 , the alpha field  752  (EVEX byte  3 , bit [ 7 ]—EH) is interpreted as the write mask control (Z) field  752 C. When U= 1  and the MOD field  842  contains  11  (signifying a no memory access operation), part of the beta field  754  (EVEX byte  3 , bit [ 4 ]-SO) is interpreted as the RL field  757 A; when it contains a  1  (round  757 A. 1 ) the rest of the beta field  754  (EVEX byte  3 , bit [ 6 - 5 ]-S 2 - 1 ) is interpreted as the round operation field  759 A, while when the RL field  757 A contains a  0  (VSIZE  757 .A 2 ) the rest of the beta field  754  (EVEX byte  3 , bit [ 6 - 5 ]-S 2 - 1 ) is interpreted as the vector length field  759 B (EVEX byte  3 , bit [ 6 - 5 ]-L 1 - 0 ). When U=1 and the MOD field  842  contains 00, 01, or 10 (signifying a memory access operation), the beta field  754  (EVEX byte  3 , bits [ 6 : 4 ]-SSS) is interpreted as the vector length field  759 B (EVEX byte  3 , bit [ 6 - 5 ]-L 1 - 0 ) and the broadcast field  757 B (EVEX byte  3 , bit [ 4 ]-B). 
     Exemplary Register Architecture 
       FIG.  9    is a block diagram of a register architecture  900  according to one embodiment of the invention. In the embodiment illustrated, there are  32  vector registers  910  that are 512 bits wide; these registers are referenced as zmm 0  through zmm 31 . The lower order 256 bits of the lower 16 zmm registers are overlaid on registers ymm 0 - 16 . The lower order 128 bits of the lower 16 zmm registers (the lower order 128 bits of the ymm registers) are overlaid on registers xmm 0 - 15 . The specific vector friendly instruction format  800  operates on these overlaid register file as illustrated in the below tables. 
     
       
         
           
               
               
               
               
             
               
                   
               
               
                 Adjustable  
                   
                   
                   
               
               
                 Vector  
                   
                 Opera- 
                   
               
               
                 Length 
                 Class 
                 tions 
                 Registers 
               
               
                   
               
             
            
               
                 Instruction  
                 A (FIG. 7A;  
                 710, 715, 
                 zmm registers (the  
               
               
                 Templates that  
                 U = 0) 
                 725, 730 
                 vector length is 64  
               
               
                 do not include 
                 B (FIG. 7B;  
                 712 
                 byte) 
               
               
                 the vector  
                 U = 1) 
                   
                 zmm registers (the  
               
               
                 length field  
                   
                   
                 vector length is 64  
               
               
                 759B 
                   
                   
                 byte) 
               
               
                 Instruction  
                 B (FIG. 7B;  
                 717, 727 
                 zmm, ymm, or xmm  
               
               
                 templates  
                 U = 1) 
                   
                 registers (the vector  
               
               
                 that do include  
                   
                   
                 length is 64 byte, 32  
               
               
                 the vector  
                   
                   
                 byte, or 16 byte)  
               
               
                 length field  
                   
                   
                 depending on the  
               
               
                 759B 
                   
                   
                 vector length 
               
               
                   
                   
                   
                 field 759B 
               
               
                   
               
            
           
         
       
     
     In other words, the vector length field  759 B selects between a maximum length and one or more other shorter lengths, where each such shorter length is half the length of the preceding length; and instructions templates without the vector length field  759 B operate on the maximum vector length. Further, in one embodiment, the class B instruction templates of the specific vector friendly instruction format  800  operate on packed or scalar single/double-precision floating point data and packed or scalar integer data. Scalar operations are operations performed on the lowest order data element position in an zmm/ymm/xmm register; the higher order data element positions are either left the same as they were prior to the instruction or zeroed depending on the embodiment. 
     Write mask registers  915 —in the embodiment illustrated, there are  8  write mask registers (k 0  through k 7 ), each 64 bits in size. In an alternate embodiment, the write mask registers  915  are 16 bits in size. As previously described, in one embodiment of the invention, the vector mask register k 0  cannot be used as a write mask; when the encoding that would normally indicate k 0  is used for a write mask, it selects a hardwired write mask of 0xFFFF, effectively disabling write masking for that instruction. 
     General-purpose registers  925 —in the embodiment illustrated, there are sixteen 64-bit general-purpose registers that are used along with the existing x86 addressing modes to address memory operands. These registers are referenced by the names RAX, RBX, RCX, RDX, RBP, RSI, RDI, RSP, and R 8  through R 15 . 
     Scalar floating point stack register file (x87 stack)  945 , on which is aliased the MMX packed integer flat register file  950 —in the embodiment illustrated, the x87 stack is an eight-element stack used to perform scalar floating-point operations on 32/64/80-bit floating point data using the x87 instruction set extension; while the MMX registers are used to perform operations on 64-bit packed integer data, as well as to hold operands for some operations performed between the MMX and XMM registers. 
     Alternative embodiments of the invention may use wider or narrower registers. Additionally, alternative embodiments of the invention may use more, less, or different register files and registers. 
     Exemplary Core Architectures, Processors, and Computer Architectures 
     Processor cores may be implemented in different ways, for different purposes, and in different processors. For instance, implementations of such cores may include: 1) a general purpose in-order core intended for general-purpose computing; 2) a high performance general purpose out-of-order core intended for general-purpose computing; 3) a special purpose core intended primarily for graphics and/or scientific (throughput) computing. Implementations of different processors may include: 1) a CPU including one or more general purpose in-order cores intended for general-purpose computing and/or one or more general purpose out-of-order cores intended for general-purpose computing; and 2) a coprocessor including one or more special purpose cores intended primarily for graphics and/or scientific (throughput). Such different processors lead to different computer system architectures, which may include: 1) the coprocessor on a separate chip from the CPU; 2) the coprocessor on a separate die in the same package as a CPU; 3) the coprocessor on the same die as a CPU (in which case, such a coprocessor is sometimes referred to as special purpose logic, such as integrated graphics and/or scientific (throughput) logic, or as special purpose cores); and 4) a system on a chip that may include on the same die the described CPU (sometimes referred to as the application core(s) or application processor(s)), the above described coprocessor, and additional functionality. Exemplary core architectures are described next, followed by descriptions of exemplary processors and computer architectures. 
     Exemplary Core Architectures 
     In-Order and Oout-of-Order Core Block Diagram 
       FIG.  10 A  is a block diagram illustrating both an exemplary in-order pipeline and an exemplary register renaming, out-of-order issue/execution pipeline according to embodiments of the invention.  FIG.  10 B  is a block diagram illustrating both an exemplary embodiment of an in-order architecture core and an exemplary register renaming, out-of-order issue/execution architecture core to be included in a processor according to embodiments of the invention. The solid lined boxes in  FIGS.  10 A-B  illustrate the in-order pipeline and in-order core, while the optional addition of the dashed lined boxes illustrates the register renaming, out-of-order issue/execution pipeline and core. Given that the in-order aspect is a subset of the out-of-order aspect, the out-of-order aspect will be described. 
     In  FIG.  10 A , a processor pipeline  1000  includes a fetch stage  1002 , a length decode stage  1004 , a decode stage  1006 , an allocation stage  1008 , a renaming stage  1010 , a scheduling (also known as a dispatch or issue) stage  1012 , a register read/memory read stage  1014 , an execute stage  1016 , a write back/memory write stage  1018 , an exception handling stage  1022 , and a commit stage  1024 . 
       FIG.  10 B  shows processor core  1090  including a front end unit  1030  coupled to an execution engine unit  1050 , and both are coupled to a memory unit  1070 . The core  1090  may be a reduced instruction set computing (RISC) core, a complex instruction set computing (CISC) core, a very long instruction word (VLIW) core, or a hybrid or alternative core type. As yet another option, the core  1090  may be a special-purpose core, such as, for example, a network or communication core, compression engine, coprocessor core, general purpose computing graphics processing unit (GPGPU) core, graphics core, or the like. 
     The front end unit  1030  includes a branch prediction unit  1032  coupled to an instruction cache unit  1034 , which is coupled to an instruction translation lookaside buffer (TLB)  1036 , which is coupled to an instruction fetch unit  1038 , which is coupled to a decode unit  1040 . The decode unit  1040  (or decoder) may decode instructions, and generate as an output one or more micro-operations, micro-code entry points, microinstructions, other instructions, or other control signals, which are decoded from, or which otherwise reflect, or are derived from, the original instructions. The decode unit  1040  may be implemented using various different mechanisms. Examples of suitable mechanisms include, but are not limited to, look-up tables, hardware implementations, programmable logic arrays (PLAs), microcode read only memories (ROMs), etc. In one embodiment, the core  1090  includes a microcode ROM or other medium that stores microcode for certain macroinstructions (e.g., in decode unit  1040  or otherwise within the front end unit  1030 ). The decode unit  1040  is coupled to a rename/allocator unit  1052  in the execution engine unit  1050 . 
     The execution engine unit  1050  includes the rename/allocator unit  1052  coupled to a retirement unit  1054  and a set of one or more scheduler unit(s)  1056 . The scheduler unit(s)  1056  represents any number of different schedulers, including reservations stations, central instruction window, etc. The scheduler unit(s)  1056  is coupled to the physical register file(s) unit(s)  1058 . Each of the physical register file(s) units  1058  represents one or more physical register files, different ones of which store one or more different data types, such as scalar integer, scalar floating point, packed integer, packed floating point, vector integer, vector floating point, status (e.g., an instruction pointer that is the address of the next instruction to be executed), etc. In one embodiment, the physical register file(s) unit  1058  comprises a vector registers unit, a write mask registers unit, and a scalar registers unit. These register units may provide architectural vector registers, vector mask registers, and general purpose registers. The physical register file(s) unit(s)  1058  is overlapped by the retirement unit  1054  to illustrate various ways in which register renaming and out-of-order execution may be implemented (e.g., using a reorder buffer(s) and a retirement register file(s); using a future file(s), a history buffer(s), and a retirement register file(s); using a register maps and a pool of registers; etc.). The retirement unit  1054  and the physical register file(s) unit(s)  1058  are coupled to the execution cluster(s)  1060 . The execution cluster(s)  1060  includes a set of one or more execution units  1062  and a set of one or more memory access units  1064 . The execution units  1062  may perform various operations (e.g., shifts, addition, subtraction, multiplication) and on various types of data (e.g., scalar floating point, packed integer, packed floating point, vector integer, vector floating point). While some embodiments may include a number of execution units dedicated to specific functions or sets of functions, other embodiments may include only one execution unit or multiple execution units that all perform all functions. The scheduler unit(s)  1056 , physical register file(s) unit(s)  1058 , and execution cluster(s)  1060  are shown as being possibly plural because certain embodiments create separate pipelines for certain types of data/operations (e.g., a scalar integer pipeline, a scalar floating point/packed integer/packed floating point/vector integer/vector floating point pipeline, and/or a memory access pipeline that each have their own scheduler unit, physical register file(s) unit, and/or execution cluster—and in the case of a separate memory access pipeline, certain embodiments are implemented in which only the execution cluster of this pipeline has the memory access unit(s)  1064 ). It should also be understood that where separate pipelines are used, one or more of these pipelines may be out-of-order issue/execution and the rest in-order. 
     The set of memory access units  1064  is coupled to the memory unit  1070 , which includes a data TLB unit  1072  coupled to a data cache unit  1074  coupled to a level 2 (L2) cache unit  1076 . In one exemplary embodiment, the memory access units  1064  may include a load unit, a store address unit, and a store data unit, each of which is coupled to the data TLB unit  1072  in the memory unit  1070 . The instruction cache unit  1034  is further coupled to a level 2 (L2) cache unit  1076  in the memory unit  1070 . The L2 cache unit  1076  is coupled to one or more other levels of cache and eventually to a main memory. 
     By way of example, the exemplary register renaming, out-of-order issue/execution core architecture may implement the pipeline  1000  as follows: 1) the instruction fetch  1038  performs the fetch and length decoding stages  1002  and  1004 ; 2) the decode unit  1040  performs the decode stage  1006 ; 3) the rename/allocator unit  1052  performs the allocation stage  1008  and renaming stage  1010 ; 4) the scheduler unit(s)  1056  performs the schedule stage  1012 ; 5) the physical register file(s) unit(s)  1058  and the memory unit  1070  perform the register read/memory read stage  1014 ; the execution cluster  1060  perform the execute stage  1016 ; 6) the memory unit  1070  and the physical register file(s) unit(s)  1058  perform the write back/memory write stage  1018 ; 7) various units may be involved in the exception handling stage  1022 ; and 8) the retirement unit  1054  and the physical register file(s) unit(s)  1058  perform the commit stage  1024 . 
     The core  1090  may support one or more instructions sets (e.g., the x86 instruction set (with some extensions that have been added with newer versions); the MIPS instruction set of MIPS Technologies of Sunnyvale, Calif.; the ARM instruction set (with optional additional extensions such as NEON) of ARM Holdings of Sunnyvale, Calif.), including the instruction(s) described herein. In one embodiment, the core  1090  includes logic to support a packed data instruction set extension (e.g., AVX 1 , AVX 2 ), thereby allowing the operations used by many multimedia applications to be performed using packed data. 
     It should be understood that the core may support multithreading (executing two or more parallel sets of operations or threads), and may do so in a variety of ways including time sliced multithreading, simultaneous multithreading (where a single physical core provides a logical core for each of the threads that physical core is simultaneously multithreading), or a combination thereof (e.g., time sliced fetching and decoding and simultaneous multithreading thereafter such as in the Intel® Hyperthreading technology). 
     While register renaming is described in the context of out-of-order execution, it should be understood that register renaming may be used in an in-order architecture. While the illustrated embodiment of the processor also includes separate instruction and data cache units  1034 / 1074  and a shared L2 cache unit  1076 , alternative embodiments may have a single internal cache for both instructions and data, such as, for example, a Level 1 (L1) internal cache, or multiple levels of internal cache. In some embodiments, the system may include a combination of an internal cache and an external cache that is external to the core and/or the processor. Alternatively, all of the cache may be external to the core and/or the processor. 
     Specific Exemplary In-Order Core Architecture 
       FIGS.  11 A-B  illustrate a block diagram of a more specific exemplary in-order core architecture, which core would be one of several logic blocks (including other cores of the same type and/or different types) in a chip. The logic blocks communicate through a high-bandwidth interconnect network (e.g., a ring network) with some fixed function logic, memory I/O interfaces, and other necessary I/O logic, depending on the application. 
       FIG.  11 A  is a block diagram of a single processor core, along with its connection to the on-die interconnect network  1102  and with its local subset of the Level 2 (L2) cache  1104 , according to embodiments of the invention. In one embodiment, an instruction decoder  1100  supports the x86 instruction set with a packed data instruction set extension. An L1 cache  1106  allows low-latency accesses to cache memory into the scalar and vector units. While in one embodiment (to simplify the design), a scalar unit  1108  and a vector unit  1110  use separate register sets (respectively, scalar registers  1112  and vector registers  1114 ) and data transferred between them is written to memory and then read back in from a level 1 (L1) cache  1106 , alternative embodiments of the invention may use a different approach (e.g., use a single register set or include a communication path that allow data to be transferred between the two register files without being written and read back). 
     The local subset of the L2 cache  1104  is part of a global L2 cache that is divided into separate local subsets, one per processor core. Each processor core has a direct access path to its own local subset of the L2 cache  1104 . Data read by a processor core is stored in its L2 cache subset  1104  and can be accessed quickly, in parallel with other processor cores accessing their own local L2 cache subsets. Data written by a processor core is stored in its own L2 cache subset  1104  and is flushed from other subsets, if necessary. The ring network ensures coherency for shared data. The ring network is bi-directional to allow agents such as processor cores, L2 caches and other logic blocks to communicate with each other within the chip. Each ring data-path is  1012 -bits wide per direction. 
       FIG.  11 B  is an expanded view of part of the processor core in  FIG.  11 A  according to embodiments of the invention.  FIG.  11 B  includes an Ll data cache  1106 A part of the L1 cache  1106 , as well as more detail regarding the vector unit  1110  and the vector registers  1114 . Specifically, the vector unit  1110  is a 16-wide vector processing unit (VPU) (see the 16-wide ALU  1128 ), which executes one or more of integer, single-precision float, and double-precision float instructions. The VPU supports swizzling the register inputs with swizzle unit  1120 , numeric conversion with numeric convert units  1122 A-B, and replication with replication unit  1124  on the memory input. Write mask registers  1126  allow predicating resulting vector writes. 
       FIG.  12    is a block diagram of a processor  1200  that may have more than one core, may have an integrated memory controller, and may have integrated graphics according to embodiments of the invention. The solid lined boxes in  FIG.  12    illustrate a processor  1200  with a single core  1202 A, a system agent  1210 , a set of one or more bus controller units  1216 , while the optional addition of the dashed lined boxes illustrates an alternative processor  1200  with multiple cores  1202 A-N, a set of one or more integrated memory controller unit(s)  1214  in the system agent unit  1210 , and special purpose logic  1208 . 
     Thus, different implementations of the processor  1200  may include: 1) a CPU with the special purpose logic  1208  being integrated graphics and/or scientific (throughput) logic (which may include one or more cores), and the cores  1202 A-N being one or more general purpose cores (e.g., general purpose in-order cores, general purpose out-of-order cores, a combination of the two); 2) a coprocessor with the cores  1202 A-N being a large number of special purpose cores intended primarily for graphics and/or scientific (throughput); and 3) a coprocessor with the cores  1202 A-N being a large number of general purpose in-order cores. Thus, the processor  1200  may be a general-purpose processor, coprocessor or special-purpose processor, such as, for example, a network or communication processor, compression engine, graphics processor, GPGPU (general purpose graphics processing unit), a high-throughput many integrated core (MIC) coprocessor (including  30  or more cores), embedded processor, or the like. The processor may be implemented on one or more chips. The processor  1200  may be a part of and/or may be implemented on one or more substrates using any of a number of process technologies, such as, for example, BiCMOS, CMOS, or NMOS. 
     The memory hierarchy includes respective one or more levels of caches  1204 A-N within cores  1202 A-N, a set or one or more shared cache units  1206 , and external memory (not shown) coupled to the set of integrated memory controller units  1214 . The set of shared cache units  1206  may include one or more mid-level caches, such as level 2 (L2), level 3 (L3), level 4 (L4), or other levels of cache, a last level cache (LLC), and/or combinations thereof. While in one embodiment a ring based interconnect unit  1212  interconnects the special purpose logic  1208 , the set of shared cache units  1206 , and the system agent unit  1210 /integrated memory controller unit(s)  1214 , alternative embodiments may use any number of well-known techniques for interconnecting such units. In one embodiment, coherency is maintained between one or more cache units  1206  and cores  1202 -A-N. 
     In some embodiments, one or more of the cores  1202 A-N are capable of multi-threading. The system agent  1210  includes those components coordinating and operating cores  1202 A-N. The system agent unit  1210  may include for example a power control unit (PCU) and a display unit. The PCU may be or include logic and components needed for regulating the power state of the cores  1202 A-N and the special purpose logic  1208 . The display unit is for driving one or more externally connected displays. 
     The cores  1202 A-N may be homogenous or heterogeneous in terms of architecture instruction set; that is, two or more of the cores  1202 A-N may be capable of execution the same instruction set, while others may be capable of executing only a subset of that instruction set or a different instruction set. 
     Exemplary Computer Architectures 
       FIGS.  13  through  16    are block diagrams of exemplary computer architectures. Other system designs and configurations known in the arts for laptops, desktops, handheld PCs, personal digital assistants, engineering workstations, servers, network devices, network hubs, switches, embedded processors, digital signal processors (DSPs), graphics devices, video game devices, set-top boxes, micro controllers, cell phones, portable media players, hand held devices, and various other electronic devices, are also suitable. In general, a huge variety of systems or electronic devices capable of incorporating a processor and/or other execution logic as disclosed herein are generally suitable. 
     Referring now to  FIG.  13   , shown is a block diagram of a system  1300  in accordance with one embodiment of the present invention. The system  1300  may include one or more processors  1310 ,  1315 , which are coupled to a controller hub  1320 . In one embodiment the controller hub  1320  includes a graphics memory controller hub (GMCH)  1390  and an Input/Output Hub (IOH)  1350  (which may be on separate chips); the GMCH  1390  includes memory and graphics controllers to which are coupled memory  1340  and a coprocessor  1345 ; the IOH  1350  couples input/output (I/O) devices  1360  to the GMCH  1390 . Alternatively, one or both of the memory and graphics controllers are integrated within the processor (as described herein), the memory  1340  and the coprocessor  1345  are coupled directly to the processor  1310 , and the controller hub  1320  in a single chip with the IOH  1350 . 
     The optional nature of additional processors  1315  is denoted in  FIG.  13    with broken lines. Each processor  1310 ,  1315  may include one or more of the processing cores described herein and may be some version of the processor  1200 . 
     The memory  1340  may be, for example, dynamic random access memory (DRAM), phase change memory (PCM), or a combination of the two. For at least one embodiment, the controller hub  1320  communicates with the processor(s)  1310 ,  1315  via a multi-drop bus, such as a frontside bus (FSB), point-to-point interface such as QuickPath Interconnect (QPI), or similar connection  1395 . 
     In one embodiment, the coprocessor  1345  is a special-purpose processor, such as, for example, a high-throughput MIC processor, a network or communication processor, compression engine, graphics processor, GPGPU, embedded processor, or the like. In one embodiment, controller hub  1320  may include an integrated graphics accelerator. 
     There can be a variety of differences between the processors  1310 ,  1315  in terms of a spectrum of metrics of merit including architectural, microarchitectural, thermal, power consumption characteristics, and the like. 
     In one embodiment, the processor  1310  executes instructions that control data processing operations of a general type. Embedded within the instructions may be coprocessor instructions. The processor  1310  recognizes these coprocessor instructions as being of a type that should be executed by the attached coprocessor  1345 . Accordingly, the processor  1310  issues these coprocessor instructions (or control signals representing coprocessor instructions) on a coprocessor bus or other interconnect, to coprocessor  1345 . Coprocessor(s)  1345  accept and execute the received coprocessor instructions. 
     Referring now to  FIG.  14   , shown is a block diagram of a first more specific exemplary system  1400  in accordance with an embodiment of the present invention. As shown in  FIG.  14   , multiprocessor system  1400  is a point-to-point interconnect system, and includes a first processor  1470  and a second processor  1480  coupled via a point-to-point interconnect  1450 . Each of processors  1470  and  1480  may be some version of the processor  1200 . In one embodiment of the invention, processors  1470  and  1480  are respectively processors  1310  and  1315 , while coprocessor  1438  is coprocessor  1345 . In another embodiment, processors  1470  and  1480  are respectively processor  1310  coprocessor  1345 . 
     Processors  1470  and  1480  are shown including integrated memory controller (IMC) units  1472  and  1482 , respectively. Processor  1470  also includes as part of its bus controller unit&#39;s point-to-point (P-P) interfaces  1476  and  1478 ; similarly, second processor  1480  includes P-P interfaces  1486  and  1488 . Processors  1470 ,  1480  may exchange information via a point-to-point (P-P) interconnect  1450  using P-P interface circuits  1478 ,  1488 . As shown in  FIG.  14   , IMCs  1472  and  1482  couple the processors to respective memories, namely a memory  1432  and a memory  1434 , which may be portions of main memory locally attached to the respective processors. 
     Processors  1470 ,  1480  may each exchange information with a chipset  1490  via individual P-P interfaces  1452 ,  1454  using point to point interface circuits  1476 ,  1494 ,  1486 ,  1498 . Chipset  1490  may optionally exchange information with the coprocessor  1438  via a high-performance interface  1492  and an interconnect  1439 . In one embodiment, the coprocessor  1438  is a special-purpose processor, such as, for example, a high-throughput MIC processor, a network or communication processor, compression engine, graphics processor, GPGPU, embedded processor, or the like. 
     A shared cache (not shown) may be included in either processor or outside of both processors, yet connected with the processors via P-P interconnect, such that either or both processors&#39; local cache information may be stored in the shared cache if a processor is placed into a low power mode. 
     Chipset  1490  may be coupled to a first bus  1416  via an interface  1496 . In one embodiment, first bus  1416  may be a Peripheral Component Interconnect (PCI) bus, or a bus such as a PCI Express bus or another third generation I/O interconnect bus, although the scope of the present invention is not so limited. 
     As shown in  FIG.  14   , various I/O devices  1414  may be coupled to first bus  1416 , along with a bus bridge  1418  which couples first bus  1416  to a second bus  1420 . In one embodiment, one or more additional processor(s)  1415 , such as coprocessors, high-throughput MIC processors, GPGPU&#39;s, accelerators (such as, e.g., graphics accelerators or digital signal processing (DSP) units), field programmable gate arrays, or any other processor, are coupled to first bus  1416 . In one embodiment, second bus  1420  may be a low pin count (LPC) bus. Various devices may be coupled to a second bus  1420  including, for example, a keyboard and/or mouse  1422 , communication devices  1427  and a storage unit  1428  such as a disk drive or other mass storage device which may include instructions/code and data  1430 , in one embodiment. Further, an audio I/O  1424  may be coupled to the second bus  1420 . Note that other architectures are possible. For example, instead of the point-to-point architecture of  FIG.  14   , a system may implement a multi-drop bus or other such architecture. 
     Referring now to  FIG.  15   , shown is a block diagram of a second more specific exemplary system  1500  in accordance with an embodiment of the present invention. Like elements in  FIGS.  14  and  15    bear like reference numerals, and certain aspects of  FIG.  14    have been omitted from  FIG.  15    in order to avoid obscuring other aspects of  FIG.  15   . 
       FIG.  15    illustrates that the processors  1470 ,  1480  may include integrated memory and I/O control logic (“CL”)  1572  and  1582 , respectively. Thus, the CL  1572 ,  1582  include integrated memory controller units and include I/O control logic.  FIG.  15    illustrates that not only are the memories  1432 ,  1434  coupled to the CL  1572 ,  1582 , but also that I/O devices  1514  are also coupled to the control logic  1572 ,  1582 . Legacy I/O devices  1515  are coupled to the chipset  1490 . 
     Referring now to  FIG.  16   , shown is a block diagram of a SoC  1600  in accordance with an embodiment of the present invention. Similar elements in  FIG.  12    bear like reference numerals. Also, dashed lined boxes are optional features on more advanced SoCs. In  FIG.  16   , an interconnect unit(s)  1602  is coupled to: an application processor  1610  which includes a set of one or more cores  1202 A-N and shared cache unit(s)  1206 ; a system agent unit  1210 ; a bus controller unit(s)  1216 ; an integrated memory controller unit(s)  1214 ; a set or one or more coprocessors  1620  which may include integrated graphics logic, an image processor, an audio processor, and a video processor; an static random access memory (SRAM) unit  1630 ; a direct memory access (DMA) unit  1632 ; and a display unit  1640  for coupling to one or more external displays. In one embodiment, the coprocessor(s)  1620  include a special-purpose processor, such as, for example, a network or communication processor, compression engine, GPGPU, a high-throughput MIC processor, embedded processor, or the like. 
     Embodiments of the mechanisms disclosed herein may be implemented in hardware, software, firmware, or a combination of such implementation approaches. Embodiments of the invention may be implemented as computer programs or program code executing on programmable systems comprising at least one processor, a storage system (including volatile and non-volatile memory and/or storage elements), at least one input device, and at least one output device. 
     Program code, such as code  1430  illustrated in  FIG.  14   , may be applied to input instructions to perform the functions described herein and generate output information. The output information may be applied to one or more output devices, in known fashion. For purposes of this application, a processing system includes any system that has a processor, such as, for example; a digital signal processor (DSP), a microcontroller, an application specific integrated circuit (ASIC), or a microprocessor. 
     The program code may be implemented in a high level procedural or object oriented programming language to communicate with a processing system. The program code may also be implemented in assembly or machine language, if desired. In fact, the mechanisms described herein are not limited in scope to any particular programming language. In any case, the language may be a compiled or interpreted language. 
     One or more aspects of at least one embodiment may be implemented by representative instructions stored on a machine-readable medium which represents various logic within the processor, which when read by a machine causes the machine to fabricate logic to perform the techniques described herein. Such representations, known as “IP cores” may be stored on a tangible, machine readable medium and supplied to various customers or manufacturing facilities to load into the fabrication machines that actually make the logic or processor. 
     Such machine-readable storage media may include, without limitation, non-transitory, tangible arrangements of articles manufactured or formed by a machine or device, including storage media such as hard disks, any other type of disk including floppy disks, optical disks, compact disk read-only memories (CD-ROMs), compact disk rewritable&#39;s (CD-RWs), and magneto-optical disks, semiconductor devices such as read-only memories (ROMs), random access memories (RAMs) such as dynamic random access memories (DRAMs), static random access memories (SRAMs), erasable programmable read-only memories (EPROMs), flash memories, electrically erasable programmable read-only memories (EEPROMs), phase change memory (PCM), magnetic or optical cards, or any other type of media suitable for storing electronic instructions. 
     Accordingly, embodiments of the invention also include non-transitory, tangible machine-readable media containing instructions or containing design data, such as Hardware Description Language (HDL), which defines structures, circuits, apparatuses, processors and/or system features described herein. Such embodiments may also be referred to as program products. 
     Emulation (Including Binary Translation, Code Morphing, etc.) 
     In some cases, an instruction converter may be used to convert an instruction from a source instruction set to a target instruction set. For example, the instruction converter may translate (e.g., using static binary translation, dynamic binary translation including dynamic compilation), morph, emulate, or otherwise convert an instruction to one or more other instructions to be processed by the core. The instruction converter may be implemented in software, hardware, firmware, or a combination thereof. The instruction converter may be on processor, off processor, or part on and part off processor. 
       FIG.  17    is a block diagram contrasting the use of a software instruction converter to convert binary instructions in a source instruction set to binary instructions in a target instruction set according to embodiments of the invention. In the illustrated embodiment, the instruction converter is a software instruction converter, although alternatively the instruction converter may be implemented in software, firmware, hardware, or various combinations thereof.  FIG.  17    shows a program in a high level language  1702  may be compiled using an x86 compiler  1704  to generate x86 binary code  1706  that may be natively executed by a processor with at least one x86 instruction set core  1716 . The processor with at least one x86 instruction set core  1716  represents any processor that can perform substantially the same functions as an Intel processor with at least one x86 instruction set core by compatibly executing or otherwise processing (1) a substantial portion of the instruction set of the Intel x86 instruction set core or (2) object code versions of applications or other software targeted to run on an Intel processor with at least one x86 instruction set core, in order to achieve substantially the same result as an Intel processor with at least one x86 instruction set core. The x86 compiler  1704  represents a compiler that is operable to generate x86 binary code  1706  (e.g., object code) that can, with or without additional linkage processing, be executed on the processor with at least one x86 instruction set core  1716 . Similarly,  FIG.  17    shows the program in the high level language  1702  may be compiled using an alternative instruction set compiler  1708  to generate alternative instruction set binary code  1710  that may be natively executed by a processor without at least one x86 instruction set core  1714  (e.g., a processor with cores that execute the MIPS instruction set of MIPS Technologies of Sunnyvale, Calif. and/or that execute the ARM instruction set of ARM Holdings of Sunnyvale, Calif.). The instruction converter  1712  is used to convert the x86 binary code  1706  into code that may be natively executed by the processor without an x86 instruction set core  1714 . This converted code is not likely to be the same as the alternative instruction set binary code  1710  because an instruction converter capable of this is difficult to make; however, the converted code will accomplish the general operation and be made up of instructions from the alternative instruction set. Thus, the instruction converter  1712  represents software, firmware, hardware, or a combination thereof that, through emulation, simulation or any other process, allows a processor or other electronic device that does not have an x86 instruction set processor or core to execute the x86 binary code  1706 . 
     Techniques and architectures for executing an instruction with a virtual machine are described herein. In the above description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of certain embodiments. It will be apparent, however, to one skilled in the art that certain embodiments can be practiced without these specific details. In other instances, structures and devices are shown in block diagram form in order to avoid obscuring the description. 
     Reference in the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment. 
     Some portions of the detailed description herein are presented in terms of algorithms and symbolic representations of operations on data bits within a computer memory. These algorithmic descriptions and representations are the means used by those skilled in the computing arts to most effectively convey the substance of their work to others skilled in the art. An algorithm is here, and generally, conceived to be a self-consistent sequence of steps leading to a desired result. The steps are those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like. 
     It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the discussion herein, it is appreciated that throughout the description, discussions utilizing terms such as “processing” or “computing” or “calculating” or “determining” or “displaying” or the like, refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system&#39;s registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission or display devices. 
     Certain embodiments also relate to apparatus for performing the operations herein. This apparatus may be specially constructed for the required purposes, or it may comprise a general purpose computer selectively activated or reconfigured by a computer program stored in the computer. Such a computer program may be stored in a computer readable storage medium, such as, but is not limited to, any type of disk including floppy disks, optical disks, CD-ROMs, and magnetic-optical disks, read-only memories (ROMs), random access memories (RAMs) such as dynamic RAM (DRAM), EPROMs, EEPROMs, magnetic or optical cards, or any type of media suitable for storing electronic instructions, and coupled to a computer system bus. 
     The algorithms and displays presented herein are not inherently related to any particular computer or other apparatus. Various general purpose systems may be used with programs in accordance with the teachings herein, or it may prove convenient to construct more specialized apparatus to perform the required method steps. The required structure for a variety of these systems will appear from the description herein. In addition, certain embodiments are not described with reference to any particular programming language. It will be appreciated that a variety of programming languages may be used to implement the teachings of such embodiments as described herein. 
     In one or more first embodiments, a processor comprises first circuitry to execute a hypervisor process, second circuitry, coupled to the first circuitry, to identify to the hypervisor process an availability of a control parameter which is to determine whether an execution of an instruction with a virtual machine (VM) is to result in a switch by the processor from a flow of the VM to a flow of the hypervisor process, wherein the execution of the instruction is to identify to the VM a hardware characteristic of the processor, and third circuitry, coupled to the first circuitry, to write a value to a repository of the control parameter, the value based on an indication, from the hypervisor process, of whether a resource of the VM is authorized to avail of a host passthrough functionality of the processor. 
     In one or more second embodiments, further to the first embodiment, the control parameter is a first control parameter, the instruction is a first instruction, the VM is a first VM, the switch is a first switch, the value is a first value, the indication is a first indication, and the resource is a first resource, wherein the second circuitry is further to identify to the hypervisor process an availability of a second control parameter which is to determine whether an execution of a second instruction with a second VM is to result in a second switch by the processor from a flow of the second VM to a flow of the hypervisor process, wherein the execution of the second instruction is to identify the hardware characteristic to the second VM, and wherein the third circuitry is further to write a second value to a repository of the second control parameter, the second value based on a second indication, from the hypervisor process, of whether a second resource of the second VM is authorized to avail of the host passthrough functionality. 
     In one or more third embodiments, further to the first embodiment or the second embodiment, the instruction is a first instruction, the VM is a first VM, the switch is a first switch, and the flow is a first flow, and wherein the control parameter which is further to determine whether an execution of a second instruction with a second VM is to result in a second switch by the processor from a second flow of the second VM to the flow of the hypervisor process, wherein the execution of the second instruction is to identify the hardware characteristic to the second VM. 
     In one or more fourth embodiments, further to any of the first through third embodiments, the instruction is a central processing unit identification (CPUID) instruction of an Intel x86 instruction set. 
     In one or more fifth embodiments, a method at a processor, the method comprises executing a hypervisor process, identifying to the hypervisor process an availability of a control parameter which is to determine whether an execution of an instruction with a virtual machine (VM) is to result in a switch by the processor from a flow of the VM to a flow of the hypervisor process, wherein the execution of the instruction is to identify to the VM a hardware characteristic of the processor, and writing a value to a repository of the control parameter, the value based on an indication, from the hypervisor process, of whether a resource of the VM is authorized to avail of a host passthrough functionality of the processor. 
     In one or more sixth embodiments, further to the fifth embodiment, the control parameter is a first control parameter, the instruction is a first instruction, the VM is a first VM, the switch is a first switch, the value is a first value, the indication is a first indication, and the resource is a first resource, wherein the method further comprises identifying to the hypervisor process an availability of a second control parameter which is to determine whether an execution of a second instruction with a second VM is to result in a second switch by the processor from a flow of the second VM to a flow of the hypervisor process, wherein the execution of the second instruction is to identify the hardware characteristic to the second VM, and writing a second value to a repository of the second control parameter, the second value based on a second indication, from the hypervisor process, of whether a second resource of the second VM is authorized to avail of the host passthrough functionality. 
     In one or more seventh embodiments, further to the fifth embodiment or the sixth embodiment, the instruction is a first instruction, the VM is a first VM, the switch is a first switch, and the flow is a first flow, and wherein the control parameter which is further to determine whether an execution of a second instruction with a second VM is to result in a second switch by the processor from a second flow of the second VM to the flow of the hypervisor process, wherein the execution of the second instruction is to identify the hardware characteristic to the second VM. 
     In one or more eighth embodiments, further to any of the fifth through seventh embodiments, the instruction is a central processing unit identification (CPUID) instruction of an Intel x86 instruction set. 
     In one or more ninth embodiments, a system comprises a memory to store first state of a hypervisor process, and second state of a virtual machine (VM) which is to be provided with the hypervisor process, a processor coupled to the memory, the processor comprising first circuitry to execute the hypervisor process, second circuitry, coupled to the first circuitry, to identify to the hypervisor process an availability of a control parameter which is to determine whether an execution of an instruction with the VM is to result in a switch by the processor from a flow of the VM to a flow of the hypervisor process, wherein the execution of the instruction is to identify to the VM a hardware characteristic of the processor, and third circuitry, coupled to the first circuitry, to write a value to a repository of the control parameter, the value based on an indication, from the hypervisor process, of whether a resource of the VM is authorized to avail of a host passthrough functionality of the processor. The system further comprises a display device coupled to the processor and to the memory, the display device to display an image based on the flow of the VM. 
     In one or more tenth embodiments, further to the ninth embodiment, the control parameter is a first control parameter, the instruction is a first instruction, the VM is a first VM, the switch is a first switch, the value is a first value, the indication is a first indication, and the resource is a first resource, wherein the second circuitry is further to identify to the hypervisor process an availability of a second control parameter which is to determine whether an execution of a second instruction with a second VM is to result in a second switch by the processor from a flow of the second VM to a flow of the hypervisor process, wherein the execution of the second instruction is to identify the hardware characteristic to the second VM, and wherein the third circuitry is further to write a second value to a repository of the second control parameter, the second value based on a second indication, from the hypervisor process, of whether a second resource of the second VM is authorized to avail of the host passthrough functionality. 
     In one or more eleventh embodiments, further to the ninth embodiment or the tenth embodiment, the instruction is a first instruction, the VM is a first VM, the switch is a first switch, and the flow is a first flow, and wherein the control parameter which is further to determine whether an execution of a second instruction with a second VM is to result in a second switch by the processor from a second flow of the second VM to the flow of the hypervisor process, wherein the execution of the second instruction is to identify the hardware characteristic to the second VM. 
     In one or more twelfth embodiments, further to any of the ninth through eleventh embodiments, the instruction is a central processing unit identification (CPUID) instruction of an Intel x86 instruction set. 
     In one or more thirteenth embodiments, one or more non-transitory computer-readable storage media having stored thereon instructions which, when executed by one or more processing units, cause the one or more processing units to perform a method comprising detecting an instruction to be executed with a virtual machine (VM) which is provided with a hypervisor process, wherein a processor executes the hypervisor process, based on the instruction, accessing a control parameter which corresponds to a resource of the VM, wherein the control parameter indicates whether the resource is authorized to avail of a host passthrough functionality of the processor, and determining, based on the control parameter, whether an execution of the instruction is to result in a switch by the processor from a flow of the VM to a flow of the hypervisor process, wherein the execution of the instruction is to identify to the VM a hardware characteristic of the processor. 
     In one or more fourteenth embodiments, further to the thirteenth embodiment, determining whether the execution of the instruction is to result in the switch comprises performing a search to determine whether a memory region, which is shared by the VM and the hypervisor process, stores information which identifies the hardware characteristic, and where a failure of the search is indicated, determining, based on the control parameter, whether the resource of the VM is authorized to avail of the host passthrough functionality. 
     In one or more fifteenth embodiments, further to the fourteenth embodiment, the method further comprises where the failure of the search is indicated and the resource of the VM is authorized to avail of the host passthrough functionality, signaling the processor to communicate the information to the VM via a host passthrough. 
     In one or more sixteenth embodiments, further to the fifteenth embodiment, the execution of the instruction further results in the information being stored to the memory region. 
     In one or more seventeenth embodiments, further to the fourteenth embodiment, the method further comprises where the failure of the search is indicated and the resource of the VM is unauthorized to avail of the host passthrough functionality, generating a signal to initiate the switch from the flow of the VM to the flow of the hypervisor process. 
     In one or more eighteenth embodiments, further to the fourteenth embodiment, the method further comprises where a success of the search is indicated, providing a result of the execution based on an access of the information in the memory region. 
     In one or more nineteenth embodiments, further to the thirteenth embodiment or the fourteenth embodiment, the instruction is a first instruction, the VM is a first VM, the control parameter is a first control parameter, the resource is a first resource, and the switch is a first switch, wherein the method further comprises detecting a second instruction to be executed with a second VM which is provided with the hypervisor process, based on the second instruction, accessing a second control parameter which corresponds to a second resource of the second VM, wherein the second control parameter indicates whether the second resource is authorized to avail of the host passthrough functionality, and determining, based on the second control parameter, whether an execution of the second instruction is to result in a second switch by the processor from a flow of the second VM to the flow of the hypervisor process, wherein the execution of the second instruction is to identify to the second VM the hardware characteristic of the processor. 
     In one or more twentieth embodiments, further to any of the thirteenth, fourteenth or nineteenth embodiments, the instruction is a first instruction, the VM is a first VM, the resource is a first resource, and the switch is a first switch, the method further comprises detecting a second instruction to be executed with a second VM which is provided with the hypervisor process, accessing the control parameter based on the second instruction, wherein the control parameter further indicates whether a second resource of the second VM is authorized to avail of the host passthrough functionality, and determining, based on the control parameter, whether an execution of the second instruction is to result in a second switch by the processor from a flow of the second VM to the flow of the hypervisor process, wherein the execution of the second instruction is to identify to the second VM the hardware characteristic of the processor. 
     In one or more twenty-first embodiments, further to any of the thirteenth, fourteenth, nineteenth, or twentieth embodiments, the instruction is a central processing unit identification (CPUID) instruction of an Intel x86 instruction set. 
     In one or more twenty-second embodiments, further to any of the thirteenth, fourteenth, nineteenth, twentieth, or twenty-first embodiments, the hypervisor process is a guest hypervisor process which is provided with a host hypervisor process. 
     In one or more twenty-third embodiments, a method comprises detecting an instruction to be executed with a virtual machine (VM) which is provided with a hypervisor process, wherein a processor executes the hypervisor process, based on the instruction, accessing a control parameter which corresponds to a resource of the VM, wherein the control parameter indicates whether the resource is authorized to avail of a host passthrough functionality of the processor, and determining, based on the control parameter, whether an execution of the instruction is to result in a switch by the processor from a flow of the VM to a flow of the hypervisor process, wherein the execution of the instruction is to identify to the VM a hardware characteristic of the processor. 
     In one or more twenty-fourth embodiments, further to the twenty-third embodiment, determining whether the execution of the instruction is to result in the switch comprises performing a search to determine whether a memory region, which is shared by the VM and the hypervisor process, stores information which identifies the hardware characteristic, and where a failure of the search is indicated, determining, based on the control parameter, whether the resource of the VM is authorized to avail of the host passthrough functionality. 
     In one or more twenty-fifth embodiments, further to the twenty-fourth embodiment, the method further comprises where the failure of the search is indicated and the resource of the VM is authorized to avail of the host passthrough functionality, signaling the processor to communicate the information to the VM via a host passthrough. 
     In one or more twenty-sixth embodiments, further to the twenty-fifth embodiment, the execution of the instruction further results in the information being stored to the memory region. 
     In one or more twenty-seventh embodiments, further to the twenty-fourth embodiment, the method further comprises where the failure of the search is indicated and the resource of the VM is unauthorized to avail of the host passthrough functionality, generating a signal to initiate the switch from the flow of the VM to the flow of the hypervisor process. 
     In one or more twenty-eighth embodiments, further to the twenty-fourth embodiment, the method further comprises where a success of the search is indicated, providing a result of the execution based on an access of the information in the memory region. 
     In one or more twenty-ninth embodiments, further to the twenty-third embodiment or the twenty-fourth embodiment, the instruction is a first instruction, the VM is a first VM, the control parameter is a first control parameter, the resource is a first resource, and the switch is a first switch, wherein the method further comprises detecting a second instruction to be executed with a second VM which is provided with the hypervisor process, based on the second instruction, accessing a second control parameter which corresponds to a second resource of the second VM, wherein the second control parameter indicates whether the second resource is authorized to avail of the host passthrough functionality, and determining, based on the second control parameter, whether an execution of the second instruction is to result in a second switch by the processor from a flow of the second VM to the flow of the hypervisor process, wherein the execution of the second instruction is to identify to the second VM the hardware characteristic of the processor. 
     In one or more thirtieth embodiments, further to any of the twenty-third, twenty-fourth, or twenty-ninth embodiments, the instruction is a first instruction, the VM is a first VM, the resource is a first resource, and the switch is a first switch, the method further comprises detecting a second instruction to be executed with a second VM which is provided with the hypervisor process, accessing the control parameter based on the second instruction, wherein the control parameter further indicates whether a second resource of the second VM is authorized to avail of the host passthrough functionality, and determining, based on the control parameter, whether an execution of the second instruction is to result in a second switch by the processor from a flow of the second VM to the flow of the hypervisor process, wherein the execution of the second instruction is to identify to the second VM the hardware characteristic of the processor. 
     In one or more thirty-first embodiments, further to any of the twenty-third, twenty-fourth, twenty-ninth, or thirtieth embodiments, the instruction is a central processing unit identification (CPUID) instruction of an Intel x86 instruction set. 
     In one or more thirty-second embodiments, further to any of the twenty-third, twenty-fourth, twenty-ninth, thirtieth, or thirty-first embodiments, the hypervisor process is a guest hypervisor process which is provided with a host hypervisor process. 
     In one or more thirty-third embodiments, one or more non-transitory computer-readable storage media having stored thereon instructions which, when executed by one or more processing units, cause the one or more processing units to perform a method comprising providing a virtual machine (VM) which is to execute a host operating system, detecting an availability of a control parameter which is to determine whether an execution of an instruction with the VM is to result in a switch by a processor from a flow of the VM to a flow of a hypervisor process, wherein the execution of the instruction is to identify to the VM a hardware characteristic of the processor, based on the availability, making a determination of whether a resource of the VM is to be authorized to avail of a host passthrough functionality of the processor, and signaling the processor to set the control parameter to a value based on the determination. 
     In one or more thirty-fourth embodiments, further to the thirty-third embodiment, the VM is a first VM, the host operating system is a first host operating system, the control parameter is a first control parameter, the instruction is a first instruction, the switch is a first switch, and the resource is a first resource, wherein the method further comprises providing a second VM which is to execute a second host operating system, detecting an availability of a second control parameter which is to determine whether an execution of a second instruction with the second VM is to result in a switch by a processor from a flow of the second VM to the flow of the hypervisor process, wherein the execution of the instruction is to identify the hardware characteristic to the second VM, based on the availability of the second control parameter, making a second determination of whether a second resource of the second VM is to be authorized to avail of the host passthrough functionality, and signaling the processor to set the second control parameter to a second value based on the second determination. 
     In one or more thirty-fifth embodiments, further to the thirty-third embodiment or the thirty-fourth embodiment, the VM is a first VM, the host operating system is a first host operating system, the instruction is a first instruction, the switch is a first switch, and the resource is a first resource, wherein the method further comprises providing a second VM which is to execute a second host operating system, wherein the control parameter is further to determine whether an execution of a second instruction with the second VM is to result in a switch by the processor from a flow of the second VM to the flow of the hypervisor process, wherein the execution of the second instruction is to identify the hardware characteristic to the second VM, based on the availability of the control parameter, making a second determination of whether a second resource of the second VM is to be authorized to avail of the host passthrough functionality, and signaling the processor to set the second control parameter to a second value based on the second determination. 
     In one or more thirty-sixth embodiments, further to any of the thirty-third through thirty-fifth embodiments, the instruction is a central processing unit identification (CPUID) instruction of an Intel x86 instruction set. 
     In one or more thirty-seventh embodiments, a method comprises providing a virtual machine (VM) which is to execute a host operating system, detecting an availability of a control parameter which is to determine whether an execution of an instruction with the VM is to result in a switch by a processor from a flow of the VM to a flow of a hypervisor process, wherein the execution of the instruction is to identify to the VM a hardware characteristic of the processor, based on the availability, making a determination of whether a resource of the VM is to be authorized to avail of a host passthrough functionality of the processor, and signaling the processor to set the control parameter to a value based on the determination. 
     In one or more thirty-eighth embodiments, further to the thirty-seventh embodiment, the VM is a first VM, the host operating system is a first host operating system, the control parameter is a first control parameter, the instruction is a first instruction, the switch is a first switch, and the resource is a first resource, wherein the method further comprises providing a second VM which is to execute a second host operating system, detecting an availability of a second control parameter which is to determine whether an execution of a second instruction with the second VM is to result in a switch by a processor from a flow of the second VM to the flow of the hypervisor process, wherein the execution of the instruction is to identify the hardware characteristic to the second VM, based on the availability of the second control parameter, making a second determination of whether a second resource of the second VM is to be authorized to avail of the host passthrough functionality, and signaling the processor to set the second control parameter to a second value based on the second determination. 
     In one or more thirty-ninth embodiments, further to the thirty-seventh embodiment or the thirty-eighth embodiment, the VM is a first VM, the host operating system is a first host operating system, the instruction is a first instruction, the switch is a first switch, and the resource is a first resource, wherein the method further comprises providing a second VM which is to execute a second host operating system, wherein the control parameter is further to determine whether an execution of a second instruction with the second VM is to result in a switch by the processor from a flow of the second VM to the flow of the hypervisor process, wherein the execution of the second instruction is to identify the hardware characteristic to the second VM, based on the availability of the control parameter, making a second determination of whether a second resource of the second VM is to be authorized to avail of the host passthrough functionality, and signaling the processor to set the second control parameter to a second value based on the second determination. 
     In one or more fortieth embodiments, further to any of the thirty-seventh through thirty-ninth embodiments, the instruction is a central processing unit identification (CPUID) instruction of an Intel x86 instruction set. 
     Besides what is described herein, various modifications may be made to the disclosed embodiments and implementations thereof without departing from their scope. Therefore, the illustrations and examples herein should be construed in an illustrative, and not a restrictive sense. The scope of the invention should be measured solely by reference to the claims that follow.