Patent Publication Number: US-2020285501-A1

Title: Communication interface of a secure interface control

Description:
BACKGROUND 
     The present invention relates generally to computer technology, and more specifically, to a communication interface of a secure interface control. 
     Cloud computing and cloud storage provides users with capabilities to store and process their data in third-party data centers. Cloud computing facilitates the ability to provision a virtual machine (VM) for a customer quickly and easily, without requiring the customer to purchase hardware or to provide floor space for a physical server. The customer may easily expand or contract the VM according to changing preferences or requirements of the customer. Typically, a cloud computing provider provisions the VM, which is physically resident on a server at the provider&#39;s data center. Customers are often concerned about the security of data in the VM, particularly since computing providers often store more than one customer&#39;s data on the same server. Customers may desire security between their own code/data and the cloud computing provider&#39;s code/data, as well as between their own code/data and that of other VMs running at the provider&#39;s site. In addition, the customer may desire security from the provider&#39;s administrators as well as against potential security breaches from other code running on the machine. 
     To handle such sensitive situations, cloud service providers may implement security controls to ensure proper data isolation and logical storage segregation. The extensive use of virtualization in implementing cloud infrastructure results in unique security concerns for customers of cloud services as virtualization alters the relationship between an operating system (OS) and the underlying hardware, be it computing, storage, or even networking hardware. This introduces virtualization as an additional layer that itself must be properly configured, managed and secured. 
     In general, a VM, running as a guest under the control of a host hypervisor, relies on that hypervisor to transparently provide virtualization services for that guest. These services include memory management, instruction emulation, and interruption processing. 
     SUMMARY 
     In accordance with one or more embodiments, a method is provided. The method is implemented by a communication interface of a secure interface control executing between the secure interface control of a computer and hardware of the computer/In this regard, the communication interface receives an instruction and determines whether the instruction is a millicoded instruction. Further, the communication interface enters a millimode comprising enabling the secure interface control to engage millicode of the hardware through the communication interface based on the instruction being the millicoded instruction. The millicode, then, executes the instruction. The technical effects and benefits of the one or more embodiments include eliminating the need for a context switch and associated processing overhead. 
     In accordance with one or more embodiments or the method embodiment above, the instruction can execute by the hardware of the computer based on the instruction not being the millicoded instruction. 
     In accordance with one or more embodiments or any of the method embodiments above, the communication interface can exit the millimode after the instruction is executed by the millicode. Therefore, the technical effects and benefits of embodiments herein include that the communication interface does not include any software context switch or any of the overhead associated with such a content switch. 
     In accordance with one or more embodiments or any of the method embodiments above, the secure interface control can be in communication with an unsecured entity or a secured entity that issues the instruction. 
     In accordance with one or more embodiments or any of the method embodiments above, the unsecured entity can include a hypervisor, the secured entity can include a secured guest, and the instruction can include an architected instruction. 
     In accordance with one or more embodiments or any of the method embodiments above, the millicode can utilize enhancements of the communication interface to access secure storage associated with the instruction in a secure execution context. 
     In accordance with one or more embodiments or any of the method embodiments above, the millicode can be an extension of the hardware that performs functions of the secure interface control upon executing the instruction. 
     In accordance with one or more embodiments or any of the method embodiments above, the millicode, acting as the secure interface control, can be dispatching a secure entity and sets an indication that a secure entity is running and loads a secure guest state into the hardware. 
     In accordance with one or more embodiments or any of the method embodiments above, the hardware can use the secure guest state to execute security checks while a secure guest domain associated with the secure entity is running. 
     In accordance with one or more embodiments, any of the method embodiments above can be implements as a computer program product or a system. 
     Additional features and advantages are realized through the techniques of the present disclosure. Other embodiments and aspects of the invention are described in detail herein and are considered a part of the invention. For a better understanding of the invention with the advantages and the features, refer to the description and to the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The specifics of the exclusive rights described herein are particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features and advantages of the embodiments of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  depicts a table for zone security according to one or more embodiments of the present invention; 
         FIG. 2  depicts virtual and absolute address spaces for performing DAT according to one or more embodiments of the present invention; 
         FIG. 3  depicts a nested, multi-part DAT to support a virtual machine (VM) running under a hypervisor according to one or more embodiments of the present invention; 
         FIG. 4  depicts a mapping of secure guest storage according to one or more embodiments of the present invention; 
         FIG. 5  depicts a system schematic of a dynamic address translation (DAT) operation according to one or more embodiments of the present invention; 
         FIG. 6  depicts a system schematic of a secure interface control memory according to one or more embodiments of the present invention; 
         FIG. 7  depicts a process flow of an import operation according to one or more embodiments of the present invention; 
         FIG. 8  depicts a process flow of an import operation according to one or more embodiments of the present invention; 
         FIG. 9  depicts a process of a donated memory operation according to one or more embodiments of the present invention; 
         FIG. 10  depicts a process flow of a transition of non-secure hypervisor pages to secure pages of a secure interface control according to one or more embodiments of the present invention; 
         FIG. 11  depicts a process flow of a secure storage access made by the secure interface control according to one or more embodiments of the present invention; 
         FIG. 12  depicts a process flow of access tagging by the secure interface control and by hardware according to one or more embodiments of the present invention; 
         FIG. 13  depicts a process flow of translations to support secure and non-secure accesses by the program and by the secure interface control according to one or more embodiments of the present invention; 
         FIG. 14  depicts a process flow of a DAT with secure storage protection by the program and the secure interface control according to one or more embodiments of the present invention; 
         FIG. 15  depicts a system including a secure interface control according to one or more embodiments of the present invention; 
         FIG. 16  depicts a process flow for a communication interface of a secure interface control of  FIG. 15  according to one or more embodiments of the present invention; 
         FIG. 17  depicts a cloud computing environment according to one or more embodiments of the present invention; 
         FIG. 18  depicts abstraction model layers according to one or more embodiments of the present invention; 
         FIG. 19  depicts a system according to one or more embodiments of the present invention; and 
         FIG. 20  depicts a node according to one or more embodiments of the present invention. 
     
    
    
     The diagrams depicted herein are illustrative. There can be many variations to the diagram or the operations described therein without departing from the spirit of the invention. For instance, the actions can be performed in a differing order or actions can be added, deleted or modified. Also, the term “coupled” and variations thereof describes having a communications path between two elements and does not imply a direct connection between the elements with no intervening elements/connections between them. All of these variations are considered a part of the specification. 
     DETAILED DESCRIPTION 
     In accordance or more embodiments, the present invention relates to providing a communication interface between a secure interface control and hardware of the same computer. The communication interface operates to move operations (e.g., instructions) from a software layer to a secure interface control provided by the lowest levels of firmware and hardware, thereby leveraging processing efficiencies provided by the hardware. 
     Turning now to an overview of technologies that are more specifically relevant to aspects of the invention, a context switch is a software process of storing a state of a task (e.g., a thread or other process) executing within a machine, so that the task can be restored and execution resumed from the same point later. A context switch enables multiple processes to share a single central processing unit (CPU) and is, therefore, an essential feature of a multitasking operating system. Context switches naturally have associated cost processing overhead. 
     Turning now to an overview of the aspects of the invention, one or more embodiments of the invention address technological problems by providing an efficient, lightweight communication interface of a secure interface control, which does not require a context switch, between software and hardware to provide additional security when running a secure domain. The communication interface, in particular, utilizes hardware to invoke secure interface control functions. The technical effects and benefits of the one or more embodiments include eliminating the need for a context switch and associated processing overhead. 
     A virtual machine (VM), running as a guest under the control of a host hypervisor (e.g., an untrusted entity), relies on that hypervisor to transparently provide virtualization services for that guest. These services can apply to any interface between a secure entity and another untrusted entity that traditionally allows access to the secure resources by this other entity. As mentioned previously, these services can include, but are not limited to memory management, instruction emulation, and interruption processing. For example, for interrupt and exception injection, the hypervisor typically reads and/or writes into a prefix area (low core) of the guest. The term “virtual machine” or “VM” as used herein refers to a logical representation of a physical machine (computing device, processor, etc.) and its processing environment (operating system (OS), software resources, etc.). The VM is maintained as software that executes on an underlying host machine (physical processor or set of processors). From the perspective of a user or software resource, the VM appears to be its own independent physical machine. The terms “hypervisor” and “VM Monitor (VMM)” as used herein refer to a processing environment or platform service that manages and permits multiple VM&#39;s to execute using multiple (and sometimes different) OS&#39;s on a same host machine. It should be appreciated that deploying a VM includes an installation process of the VM and an activation (or starting) process of the VM. In another example, deploying a VM includes an activation (or starting) process of the VM (e.g., in case the VM is previously installed or already exists). 
     In order to facilitate and support secure guests (e.g., secure entity), a technical challenge exists where additional security is required between the hypervisor and the secure guests without relying on the hypervisor, such that the hypervisor cannot access data from the VM, and hence, cannot provide services in the way described above. 
     The secure execution described herein provides a hardware mechanism to guarantee isolation between secure storage and non-secure storage as well as between secure storage belonging to different secure users. For secure guests, additional security is provided between the “untrusted” non-secure hypervisor and the secure guests. In order to do this, many of the functions that the hypervisor typically does on behalf of the guests need to be incorporated into the machine. A new secure interface control, also referred to herein as “UV”, is described herein to provide a secure interface between the hypervisor and the secure guests. The terms secure interface control and UV are used interchangeably herein. The secure interface control works in collaboration with the hardware to provide this additional security. In addition, a lower level hypervisor may be providing virtualization for this untrusted hypervisor and, if this lower level hypervisor is implemented in trusted code, it can also be part of the secure interface control. 
     The secure interface control, in one example, is implemented in internal, secure, and trusted hardware and/or firmware. For a secure guest or entity, the secure interface control provides the initialization and maintenance of the secure environment as well as the coordination of the dispatch of these secure entities on the hardware. While the secure guest is actively using data and it is resident in host storage, it is kept “in the clear” in secure storage. Secure guest storage can be accessed by that single secure guest—this being strictly enforced by the hardware. That is, the hardware prevents any non-secure entity (including the hypervisor or other non-secure guests) or different secure guest from accessing that data. In this example, the secure interface control runs as a trusted part of the lowest levels of firmware. The lowest level, or millicode, is really an extension of the hardware and is used to implement the complex instructions and functions defined for example in zAarchitecture® from IBM. Millicode has access to all parts of storage, which in the context of secure execution, includes its own secure UV storage, non-secure hypervisor storage, secure guest storage, and shared storage. This allows it to provide any function needed by the secure guest or by the hypervisor in support of that guest. The secure interface control also has direct access to the hardware which allows the hardware to efficiently provide security checks under the control of conditions established by the secure interface control. 
     In accordance with one or more embodiments of the present invention, the software uses an UV Call (UVC) instruction to request the secure interface control to perform a specific action. For example, the UVC instruction can be used by the hypervisor to initialize the secure interface control, create the secure guest domain (e.g., secure guest configuration), and create the virtual CPUs within that secure configuration. It can also be used to import (decrypt and assign to secure guest domain) and export (encrypt and allow host access to) a secure guest page as part of the hypervisor page-in or page-out operations. In addition, the secure guest has the ability to define storage shared with the hypervisor, make secure-storage shared, and make shared-storage secure. 
     Turning now to  FIG. 1 , a table  100  for zone security is generally shown in accordance with one or more embodiments of the present invention. The zone-security table  100  shown in  FIG. 1  is maintained by the secure interface control and is used by the secure interface control and hardware to guarantee secure access to any page accessed by a secure entity. The zone-security table  100  is indexed by the host absolute address  110 . That is, there is one entry for each page of host absolute storage. Each entry includes information that is used to verify the entry as belonging to the secure entity making the access. 
     Further, as shown in  FIG. 1 , the zone-security table  100  includes a secure domain ID  120  (identifies the secure domain associated with this page); a UV-bit  130  (indicates that this page was donated to the secure interface control and is owned by the secure interface control); a disable address compare (DA)-bit  140  (used to disable the host address pair compare in certain circumstances such as when a secure interface control page that is defined as host absolute does not have an associated host virtual address); a shared (SH)-bit  150  (indicates that the page is shared with the non-secure hypervisor) and a host virtual address  160  (indicates the host virtual address registered for this host absolute address, which is referred to as the host-address pair). Note that a host-address pair indicates a host absolute and associated, registered host virtual address. The host-address pair represents the mapping of this page, once imported by the hypervisor, and the comparison guarantees that the host does not remap that page while it is being used by the guest. 
     Dynamic address translation (DAT) is used to map virtual storage to real storage. When a guest VM is running as a pageable guest under the control of a hypervisor, the guest uses DAT to manage pages resident in its memory. In addition, the host, independently, uses DAT to manage those guest pages (along with its own pages) when the pages are resident in its memory. The hypervisor uses DAT to provide isolation and/or sharing of storage between different VMs as well as to prevent guest access to hypervisor storage. The hypervisor has access to all of the guests&#39; storage when guests are running in a non-secure mode. 
     DAT enables isolation of one application from another while still permitting them to share common resources. Also, it permits the implementation of VMs, which may be used in the design and testing of new versions of OSs along with the concurrent processing of application programs. A virtual address identifies a location in virtual storage. An address space is a consecutive sequence of virtual addresses, together with the specific transformation parameters (including DAT tables) which allow each virtual address to be translated to an associated absolute address which identifies that address with a byte location in storage. 
     DAT uses a multi-table lookup to translate the virtual address to the associated absolute address. This table structure is typically defined and maintained by a storage manager. This storage manager transparently shares the absolute storage between multiple programs by paging out one page, for example, to bring in another page. When the page is paged-out, the storage manager will set an invalid bit in the associated page table, for example. When a program tries to access a page that was paged-out, the hardware will present a program interruption, often referred to as a page fault, to the storage manager. In response, the storage manager will page-in the requested page and reset the invalid bit. This is all done transparent to the program and allows the storage manager to virtualize the storage and share it among various different users. 
     When a virtual address is used by a CPU to access main storage, it is first converted, by means of DAT, to a real address, and then, by means of prefixing, to an absolute address. The designation (origin and length) of the highest-level table for a specific address space is called an address-space-control element (ASCE) and defines the associated address space. 
     Turning now to  FIG. 2 , example virtual address spaces  202  and  204  and an absolute address space  206  for performing DAT are generally shown in accordance with one or more embodiments of the present invention. In the example shown in  FIG. 2 , there are two virtual address spaces: virtual address space  202  (defined by address space control element (ASCE) A  208 ) and virtual address space  204  (defined by ASCE B  210 ). Virtual pages A1.V  212   a   1 , A2.V  212   a   2 , and A3.V  212   a   3  are mapped, by the storage manager in a multi-table (segment  230  &amp; page tables  232   a ,  232   b ) lookup, using ASCE A  208 , to absolute pages A1.A  220   a   1 , A2.A  220   a   2  and A3.A  220   a   3 . Similarly, virtual pages B1.V  214   b   1  and B2.V  214   b   2  are mapped in a two-table  234  &amp;  236  lookup, using ASCE B  210 , to absolute pages B1.A  222   b   1  and B2.A  222   b   2 , respectively. 
     Turning now to  FIG. 3 , an example of a nested, multi-part DAT translation used to support a VM running under a hypervisor is generally shown in accordance with one or more embodiments of the present invention. In the example shown in  FIG. 3 , guest A virtual address space A  302  (defined by guest ASCE (GASCE) A  304 ) and guest B virtual address space B  306  (defined by GASCEB  308 ) both reside in a shared host (hypervisor) virtual address space  325 . As shown, virtual page A1.GV  310   a   1 , A2.GV  310   a   2 , and A3.GV  310   a   3 , belonging to guest A, are mapped, by the guest A storage manager, using GASCEA  304  to guest absolute pages A1.HV  340   a   1 , A2.HV  340   a   2 , and A3.HV  340   a   3 , respectively; virtual page B1.GV  320   b   1  and B2.GV  320   b   2 , belonging to guest B, are mapped, independently by the guest B storage manager, using GASCEB  308  to guest absolute pages B1.HV  360   b   1  and B2.HV  360   b   2 , respectively. In this example, these guest absolute pages map directly into the shared host virtual address space  325  and subsequently go through an additional host DAT translation to a host absolute address space  330 . As shown, host virtual addresses A1.HV  340   a   1 , A3.HV  340   a   3 , and B1.HV  360   b   1  are mapped, by the host storage manager using host ASCE (HASCE)  350  to A1.HA  370   a   1 , A3.HA  370   a   3 , and B1.HA  370   b   1 . Host virtual address A2.HV  340   a   2 , belonging to guest A, and B2.HV  360   b   2 , belonging to guest B, are both mapped to the same host absolute page AB2.HA  380 . This enables data to be shared between these two guests. During the guest DAT translation, each of the guest table addresses is treated as a guest absolute and undergoes an additional, nested host DAT translation. 
     Embodiments of the present invention described herein provide secure guest and UV storage protection. Access to secure storage by non-secure guests and the hypervisor is prohibited. The hypervisor provides that, for a given resident secure guest page, the following occurs. The associated host absolute address is only accessible through a single hypervisor (host) DAT mapping. That is, there is a single host virtual address that maps to any given host absolute address assigned to a secure guest. The hypervisor DAT mapping (host virtual to host absolute) associated with a given secure guest page does not change while it is paged-in. The host absolute page associated with a secure guest page is mapped for a single secure guest. 
     Sharing of storage between secure guests is also prohibited according to one or more embodiments of the present invention. Storage is shared between a single secure guest and the hypervisor under control of the secure guest. UV storage is secure storage and is accessible by the secure control interface but not the guests/hosts. Storage is allocated to the secure control interface by the hypervisor. According to one or more embodiments of the present invention, any attempted violation of these rules is prohibited by the hardware and secure control interface. 
     Turning now to  FIG. 4 , an example of mapping of secure guest storage is generally shown in accordance with one or more embodiments of the present invention.  FIG. 4  resembles  FIG. 3 , except that the example of  FIG. 4  does not allow for sharing of storage between secure guest A and secure guest B. In the non-secure example of  FIG. 3 , both host virtual address A2.HV  340   a   2 , belonging to guest A, and B2.HV  360   b   2 , belonging to guest B, are mapped to the same host absolute page AB2.HA  380 . In the secure guest storage example of  FIG. 4 , host virtual address A2.HV  340   a   2 , belonging to guest A, maps to host absolute address A2.HA  490   a , whereas B2.HV  360   b   2 , belonging to guest B, maps to its own B2.HA  490   b . In this example, there is no sharing between secure guests. 
     While the secure guest page resides on disk, it is encrypted. When the hypervisor pages-in a secure guest page, it issues a UV Call (UVC), which causes the secure control interface to mark the page as secure (unless shared), decrypt it (unless shared), and register it (in the zone-security table) as belonging to the appropriate secure guest (guest A, for example). In addition, it registers the associated host virtual address (A3.HV  340   a   3 , for example) to that host absolute page (referred to as host-address pair). If the hypervisor fails to issue the correct UVC, it receives an exception when trying to access the secure guest page. When the hypervisor pages out a guest page, a similar UVC is issued which encrypts the guest page (unless shared) before marking the guest page as non-secure and registering it in the zone-security table as non-secure. 
     In an example having five given host absolute pages K, P, L, M, and N, each of the host absolute pages are marked as secure by the secure control interface when the hypervisor pages them in. This prevents non-secure guests and the hypervisor from accessing them. Host absolute pages K, P, and M are registered as belonging to guest A when the hypervisor pages them in; host absolute pages L and N are registered to guest B when paged-in by the Hypervisor. Shared pages, pages shared between a single secure guest and the hypervisor, are not encrypted or decrypted during paging. They are not marked as secure (allows access by hypervisor) but are registered with a single secure guest domain in the zone-security table. 
     In accordance with one or more embodiments of the present invention, when a non-secure guest or the hypervisor tries to access a page that is owned by a secure guest, the hypervisor receives a secure-storage access (PIC3D) exception. No additional translation step is required to determine this. 
     In accordance with one or more embodiments, when a secure entity tries to access a page, the hardware performs an additional translation check that verifies that the storage does indeed belong to that particular secure guest. If not, a non-secure access (PIC3E) exception is presented to the hypervisor. In addition, if the host virtual address being translated does not match the host virtual address from the registered host-address pair in the zone-security table, a secure-storage violation (‘3F’x) exception is recognized. To enable sharing with the hypervisor, a secure guest may access storage that is not marked as secure as long as the translation checks allow for access. 
     Turning now to  FIG. 5 , a system schematic  500  of a DAT operation is generally shown in accordance with one or more embodiments of the present invention. The system schematic  500  includes a host primary virtual address space  510  and a host home virtual address space  520 , from which pages are translated (e.g., see host DAT translation  525 ; note that the dotted lines represent mapping through the DAT translation  525 ) to a hypervisor (host) absolute address space  530 . For instance,  FIG. 5  illustrates the sharing of host absolute storage by two different host virtual address spaces and also the sharing of one of those host virtual addresses between not only two guests but, in addition, with the host itself. In this regard, the host primary virtual address space  510  and the host home virtual address space  520  are examples of two host virtual address spaces, each of which is addressed by a separate ASCE, the host primary ASCE (HPASCE)  591  and host home ASCE (HHASCE)  592 , respectively. Note that all secure interface control storage (both virtual and real) is donated by the hypervisor and marked as secure. Once donated, the secure interface control storage can only be accessed by the secure interface control for as long as an associated secure entity exists. 
     As illustrated, the host primary virtual address space  510  includes a Guest A absolute page A1.HV, a Guest A absolute page A2.HV, a guest B absolute page B1.HV, and a host virtual page H3.HV. The host home virtual address space  520  includes a secure-interface-control virtual page U1.HV, a host virtual page H1.HV, and a host virtual page H2.HV. 
     In accordance with one or more embodiments of the present invention, all secure guest (e.g., secure Guest A &amp; secure Guest B) storage is registered, in the zone-security table described herein, as belonging to a secure guest configuration, and the associated host virtual address (e.g., A1.HV, A2.HV, B1.HV) is also registered as part of a host-address pair. In one or more embodiments, all secure guest storage is mapped in the host primary virtual space. In addition, all secure interface control storage is registered, also in the zone-security table, as belonging to the secure interface control and may be further differentiated in the zone-security table based on the associated secure guest domain. In accordance with one or more embodiments of the present invention, UV virtual storage is mapped in host home virtual space and the associated host virtual address is registered as part of the host-address pair. In accordance with one or more embodiments, UV real storage does not have an associated host virtual mapping, and the DA bit in the zone-security table (which indicates that the virtual address comparison is disabled) is set to indicate this. Host storage is marked as non-secure and is also registered in the zone-security table as non-secure. 
     Thus, in the case where ‘guest absolute=host virtual,’ the hypervisor (host) primary DAT tables (defined by the HPASCE  591 ) translate the pages of the host primary virtual address space  510  as follows: the Guest A Absolute Page A1.HV is mapped to a Host Absolute A1.HA belonging to Secure Guest A; the Guest A Absolute Page A2.HV is mapped to a Host Absolute A2.HA belonging to Secure Guest A; the Guest B Absolute Page B1.HV is mapped to a Host Absolute B1.HA belonging to Secure Guest B; and the Host Virtual Page H3.HV is mapped to a Host Absolute Page H3.HA Non-Secure Host (and there is no host-address pair since it is non-secure). Further, the hypervisor (host) home DAT tables (defined by the HHASCE  592 ) translate the pages of the host home virtual address space  520  as follows: the Secure Interface Control Virtual Page U1.HV is mapped to a Host Absolute Page U1.HA defined as Secure UV Virtual; the Host Virtual Page H1.HV is mapped to a Host Absolute Page H1.HA defined as Non-Secure; and the Host Virtual Page H2.HV is mapped to a Host Absolute Page H2.HA defined as Non-Secure. There is no host-address pair associated with either H1.HA or H2.HA since they are non-secure. 
     In operation, if a secure guest tries to access a secure page assigned to the secure interface control, a secure-storage violation (‘3F’X) exception is presented by the hardware to the hypervisor. If a non-secure guest or the hypervisor tries to access any secure page (including those assigned to the secure interface control), a secure-storage access (‘3D’X) exception is presented by the hardware to the hypervisor. Alternatively, an error condition can be presented for attempted accesses made to secure interface control space. If the hardware detects a mismatch in the secure assignment (e.g., the storage is registered in the zone-security table as belonging to a secure guest rather than to the secure interface control, or there is mismatch in host-address pair being used with the registered pair) on a secure interface control access, a check is presented. 
     In other words, the host primary virtual address space  510  includes host virtual pages A1.HV and A2.HV (belonging to secure guest A) and B1.HV (belonging to secure guest B), which map to host absolute A1.HA, A2.HA, and B1.HA, respectively. In addition, the host primary virtual address space  510  includes host (hypervisor) page H3.HV, which maps to host absolute H3.HA. The host home virtual space  520  includes two host virtual pages H1.HV and H2.HV, which map into host absolute pages H1.HA and H2.HA. Both the host primary virtual address space  510  and the host home virtual address space  520  map into the single host absolute  530 . The storage pages belonging to secure guest A and secure guest B are marked as secure and registered in the zone-security table  100  shown in  FIG. 1  with their secure domains and associated host virtual addresses. The host storage, on the other hand, is marked as non-secure. When the hypervisor is defining the secure guests, it must donate host storage to the secure interface control to use for secure control blocks needed in support of these secure guests. This storage can be defined in either host absolute or host virtual space and, in one example, specifically, in host home virtual space. Returning to  FIG. 5 , a host absolute pages U1.HA and U2.HA Secure UV Absolute is secure-interface-control storage that is defined as host absolute storage. As a result, these pages are marked as secure and registered in the zone-security table  100  shown in  FIG. 1  as belonging to the secure interface control and with an associated secure domain. Since the pages are defined as host absolute addresses, there is no associated host virtual address so the DA-bit is set in the zone-security table  100 . 
     After the translation, an example of the Hypervisor (Host) Absolute Address Space  530  can be found in  FIG. 6 . The  FIG. 6  a system schematic  600  regarding a secure interface control memory is depicted according to one or more embodiments of the present invention. The system schematic  600  illustrates a Hypervisor (Host) Absolute Address Space  630  including a Host Absolute Page A2.HA Secure Guest A (for A2.HV); a Host Absolute Page B1.HA Secure Guest B (for B1.HV); a Host Absolute Page H1.HA Non-Secure (Host); a Host Absolute Page H2.HA Non-Secure (Host); a Host Absolute Page U3.HA Secure UV Real (no HV mapping); a Host Absolute Page U1.HA Secure UV Virtual (for U1.HV); and a Host Absolute Page A1.HA Secure Guest A (for A1.HV). 
     Turning now to  FIG. 7 , a process flow  700  for an import operation is generally shown according to one or more embodiments of the present invention. When a secure guest accesses a page that was paged-out by the hypervisor, a sequence of events such as that shown in the process flow  700  occur in order to securely bring that page back in. The process flow  700  beings at block  705 , where the secure guest accesses the guest virtual page. Since the page, for example, is invalid, the hardware presents a host page fault, indicated by program-interruption-code 11 (PIC11), to the hypervisor (see block  715 ). The hypervisor, in turn, identifies an available non-secure host absolute page for this guest page (see block  720 ) and pages-in the encrypted guest page to the identified host absolute page (see block  725 ). 
     At block  730 , the host absolute page is then mapped in the appropriate (based on host virtual address) host DAT tables. At block  735 , the hypervisor host then re-dispatches the secure guest. At block  740 , the secure guest re-accesses the guest secure page. The page fault no longer exists but since this a secure guest access and the page is not marked as secure in the zone-security table  100  of  FIG. 100 , the hardware presents a non-secure-storage exception (PIC3E) to the hypervisor, at block  745 . This PIC3E prevents access by the guest to this secure page until the necessary import has been issued. Next, the process flow  700  proceeds to “A”, which is connected to  FIG. 8 . 
     Turning now to  FIG. 8 , a process flow  800  for performing an import operation is generally shown in accordance with one or more embodiments of the present invention. A well-behaved hypervisor (e.g., performing in an expected manner without errors), in response to the PIC3E, will issue an import UVC (see block  805 ). Note that at this point, a page to be imported is marked as non-secure and can only be accessed by the hypervisor, other non-secure entities, and the secure interface control. It cannot be accessed by secure guests. 
     As part of the import UVC, the trusted firmware acting as the secure interface control checks to see if this page is already locked by the secure interface control (see decision block  810 ). If it is, the process flow  800  proceeds to block  820 . At block  820 , a “busy” return code is returned to the hypervisor that will, in response, delay (see block  825 ) and reissue the Import UVC (the process flow  800  returns to block  805 ). If the page is not already locked then, the process flow  800  proceeds to decision block  822 . 
     At decision block  822 , the secure interface control checks to see if the page is a page which is shared with the non-secure hypervisor. If it is shared (the process flow  800  proceeds to decision block  824 ), the secure interface control registers the host absolute address in the zone-security table with the associated secure guest domain, host virtual address and as shared. This page remains marked as non-secure. This completes the import UVC and the page is now available to be accessed by the guest. Processing continues with the hypervisor re-dispatching guest (block  830 ) and the secure guest accessing the page successfully (block  835 ). 
     If the host virtual page to be imported is not shared with the hypervisor (the process flow  800  proceeds to block  840 ), the secure interface control will mark the page as secure, so that the hypervisor can no longer access the page. At block  845 , the secure interface control locks the page, so that no other UVC can modify the page status. Once the lock is set (at block  850 ), the secure interface control will verify that the contents of the guest page did not change while it was encrypted. If they did change then an error return code is returned to the hypervisor, otherwise, the secure interface control will decrypt the secure page. 
     At block  855 , the secure interface control unlocks the page, allowing access by other UVCs, registers the page in the zone-security table, as secure and associated with the appropriate guest domain and host virtual address to complete the host-address HV-&gt;HA pair. This allows access by the guest and completes the UVC. 
     Turning now to  FIG. 9 , a process flow  900  regarding a donated memory operation is generally shown in accordance with one or more embodiments of the present invention. The process flow  900  begins at block  905 , where a hypervisor issues a query-UVC to the secure interface control. At block  910 , the secure interface control returns data (e.g., Query UVC). This data can include an amount of base zone-specific host-absolute storage required; an amount of base secure-guest-domain-specific host-absolute storage required; an amount of variable secure-guest-domain-specific host-virtual storage required per MB; and/or amount of base secure-guest-CPU-specific host-absolute storage required. 
     At block  915 , the hypervisor reserves base host-absolute zone-specific storage (e.g., based on a size returned by query UVC). At block  920 , the hypervisor issues an initialization to the secure interface control. In this regard, the hypervisor can issue an initialize UVC that provides donated storage for the UV control blocks that are needed to coordinate between the secure guest configurations for the entire zone. The initialize UVC specifies a base zone-specific storage origin. 
     At block  925 , the secure interface control implements the initialization (e.g., initialize UVC) by registering donated storage to UV and marking as secure. For the initialize UVC, the secure interface control can mark donated storage as secure; assign some of that donated storage for the zone-security table; and register the donated storage in zone-security table for UV use with a unique secure-domain, but with no associated secure-guest-domain and as having no associated host-virtual address pair. 
     At block  930 , the hypervisor reserves storage (e.g., base and variable secure-guest-domain-specific storage). For example, the hypervisor reserves base and variable (e.g., based on a size of secure-guest-domain storage) secure-guest-domain-specific storage (e.g., a size returned by the query UVC). At block  935 , the hypervisor issues a create configuration to the secure interface control. In this regard, the hypervisor can issue a create-secure-guest-config UVC that specifies base and variable secure-guest-domain-specific storage origin. Further, the create-secure-guest-config UVC provides donated storage for the UV control blocks that are needed to support this secure guest configuration. 
     At block  940 , the secure interface control implements the create configuration (e.g., create-secure-guest-config UVC). For the create-secure-guest-config UVC, the secure interface control can mark donated storage as secure; register the donated storage in the zone-security table for UV use; and register the donated storage with the associated secure-guest-domain. The donated base (host-absolute) storage is registered as having no associated host-virtual address pair. The donated variable (host-virtual) storage is registered with the associated host-virtual address pair. 
     At block  945 , the hypervisor reserves base secure-guest-CPU-specific storage (e.g., a size returned by the query-UV). At block  950 , the hypervisor specifies a storage origin. For instance, the hypervisor issues to the UV create-secure-guest-CPU that specifies a base secure-guest-CPU-specific storage origin. At block  955 , the secure interface control implements the create-CPU (e.g., create-secure-guest-CPU UVC). For the create-secure-guest-CPU UVC, the secure interface control can mark donated storage as secure and register donated storage in the zone-security table for UV use, but with no associated secure-guest-domain and as having no associated host-virtual address pair. 
     Turning now to  FIG. 10 , a process flow  1000  regarding a transition of non-secure hypervisor pages to secure pages of a secure interface control is generally shown in accordance with one or more embodiments of the present invention. In the process flow  1000 , three hypervisor pages are shown (e.g., a non-secure hypervisor Page A, a non-secure hypervisor Page B, and a non-secure hypervisor Page C). 
     The hypervisor (non-secure) Pages A, B and C can be accessed by a non-secure entity (including the hypervisor). Further, hypervisor (non-secure) Pages A, B and C are marked as non-secure (NS), along with registered in a zone-security table (e.g., the zone-security table  100  shown in  FIG. 1 ) as non-secure and non-shared. At arrow  1005 , an initialize UVC is issued, which transitions Guest Page A to secure interface control real storage page  1010  associated with an entire zone (UV2). The secure interface control real storage  1010  can be marked as secure, along with registered in a zone-security table (e.g., the zone-security table  100  shown in  FIG. 1 ) as UV with no secure guest domain and no hypervisor to host absolute (HV-&gt;HA) mapping. Instead it is registered with a unique UV2 secure domain and the DA-bit is set to 1. Note that the secure interface control real storage  1010  can be accessed by the secure interface control as real. 
     From the hypervisor (Non-secure) Page B, at arrow  1025 , create-SG-config or create-SG-CPU UVC is issued, which transitions this page to a secure interface control real storage  1030  associated with a secure guest domain (UVS). The secure interface control real storage  1030  can be marked as secure, along with registered in a zone-security table (e.g., the zone-security table  100  shown in  FIG. 1 ) as UV with an associated secure guest domain and no hypervisor to host absolute (HV-&gt;HA) mapping (i.e., DA-bit=1). Note that the secure interface control real storage  1010  can be accessed by the secure interface control as real on behalf of a secure guest domain. 
     From the hypervisor (non-secure) Page C, at arrow  1045 , create-SG-config UVC is issued, which transitions this page to a secure interface control virtual storage  1050  associated with a secure guest domain (UVV). The secure interface control virtual storage  1050  can be marked as secure, along with registered in a zone-security table (e.g., the zone-security table  100  shown in  FIG. 1 ) as UV with a secure guest domain and hypervisor to host absolute (HV-&gt;HA) mapping. Note that the secure interface control virtual storage  1050  can be accessed as UV virtual on behalf of a secure guest domain. 
     Turning now to  FIG. 11 , a process flow  1100  regarding a secure storage access made by the program or the secure interface control is depicted in accordance with one or more embodiments. This represents the situation where the secure interface control is going to access guest storage or secure interface control storage and must tag that access correctly in order to allow the hardware to verify the security of that access.  1100  describes this tagging of storage accesses by the secure interface control. The process flow  1100  begins at block  1110 , where the secure interface control determines whether it is making an access to a secure interface control storage. 
     If this is not an access to the secure interface control storage, then the process flow  1100  proceeds to decision block  1112  (as shown by the NO arrow). At decision block  1112 , the secure interface control determines whether it is making an access to a secure guest storage. If this is not an access to the secure guest storage, then the process flow  1100  proceeds to proceeds to “B” (which is connected to process flow  1200  of  FIG. 12 ) which will use the default setting for non-secure accesses. If this is an access to the secure guest storage, then the process flow  1100  proceeds to decision block  1113 , where the secure interface control determines if a default secure guest domain is being used. If yes, then the process flow  1100  proceeds to proceeds to “B” (which is connected to process flow  1200  of  FIG. 12 ) which will use the default setting for secure guest accesses. If no, then the process flow  1100  proceeds to block  1114 . At block  1114 , an appropriate secure guest domain is loaded into SG-secure-domain register (and proceeds to “B”, which is connected to process flow  1200  of  FIG. 12 ). 
     If this is an access to the secure interface control storage, then the process flow  1100  proceeds to block  1120  (as shown by the YES arrow). At block  1120 , the access is tagged as secure-UV (e.g., uses UV-secure-domain register). 
     The process flow  1100  then proceeds to decision block  1130 , where the secure interface control determines whether this is an access to UVV space (e.g., SG-Config Variable Table). If it is an access to UVV space, then the process flow  1100  proceeds to block  1134  (as shown by the YES arrow). At block  1134 , the access is tagged as virtual. At block  1136 , an applicable secure guest domain is loaded into UV-secure-domain register. At block  1138 , DAT translation and access storage is ready to begin. Returning to decision block  1130 , if this is not an access to UVV space, then the process flow  1100  proceeds to block  1140  (as shown by the NO arrow). At block  1140 , the access is tagged as real. 
     At decision block  1150 , the secure interface control determines whether this is an access to UVS space (e.g., SG Configuration or CPU table). If this is an access to UVS space, then the process flow  1100  proceeds to block  1136  (as shown by the YES arrow). If this is not an access to UVS space, then the process flow  1100  proceeds to block  1170  (as shown by the NO arrow). This access would then be an access to UV2 space (e.g., Zone-Security Table). At block  1170 , a unique UV2 secure domain is loaded into UV-secure-domain register. 
       FIG. 12  depicts a process flow  1200  in accordance with one or more embodiments of the present invention. When a guest is dispatched, SIE Entry firmware can indicate to the hardware that a guest is running (e.g., guest mode active) and can indicate whether the guest is secure. If the guest is secure, the associated secure guest domain can be loaded into the hardware (e.g., in the SG-secure-domain register). When a program is accessing storage, the hardware can tag the access based on the current state of the program at the time of the access.  FIG. 12  illustrates an example of this process in process flow  1200 . At block  1205 , the hardware can determine whether the machine is currently running in guest mode and if not, can tag the access as being a host access at block  1210  and as being a non-secure access at block  1215 . If the machine is running in guest mode at block  1205 , the access can be tagged as a guest access at block  1220  and further determine whether the current guest is a secure guest at block  1225 . If the guest is not secure, the access can be tagged as non-secure at block  1215 . If the guest is secure, the hardware can tag the guest as secure at block  1230 , which can associate the secure guest with the SG-secure-domain register that was loaded when the secure guest was dispatched. For both non-secure and secure guests, a DAT status can be checked at block  1235 . The access can be tagged as real at block  1240 , if DAT is off. The access can be tagged as virtual at block  1245 , if DAT is on. Once the access is tagged as real at block  1240  with DAT off or as virtual at block  1245  with DAT on, the hardware is ready to begin translation and access storage at block  1250 , as further described in  FIG. 13 . 
       FIG. 13  depicts an example of translation done by the hardware to support both secure and non-secure accesses in process flow  1300  in accordance with one or more embodiments of the present invention. At block  1305 , the hardware can determine whether the access is tagged as a guest translation, and if so, and the access is virtual at block  1310 , then guest DAT can be performed at block  1315 . During guest DAT translation, there can be nested, intermediate fetches for guest DAT tables. The table fetches can be tagged as guest real and as secure if the original translation was tagged as secure. The table fetches can also follow the translation process of process flow  1300 . After the guest DAT is performed for an access tagged as guest virtual at block  1315  and for any access tagged as guest real at block  1310  (virtual=No), guest prefixing and guest memory offset can be applied at block  1320 . At the completion of the guest translation process, the resulting address can be tagged as host virtual and as secure if the original guest translation was tagged as secure at block  1325 . The process  1300  can continue as for any access tagged as host virtual. If the original access is a host access at block  1305 , (guest=No) and virtual at block  1330 , then host DAT can be performed block  1335 . Host table fetches can be marked as non-secure at block  1335 . After host DAT is performed at block  1335 , or if the original host access was tagged as real (virtual=No) at block  1330 , then host prefixing can be applied at block  1340 . The resulting address can be a host absolute address at block  1345 . 
       FIG. 14  depicts an example of DAT translation with secure storage protection that can be performed by the hardware in process flow  1400  in accordance with one or more embodiments of the present invention. Continuing from block  1345  of  FIG. 13 , if a secure-UV access is identified at block  1405 , then the hardware can verify whether the storage is registered as secure-UV storage at block  1410 , and if not, an error is presented at block  1415 . A secure-UV access can be made by the secure control interface when accessing UV storage. If the storage is registered as secure-UV storage at block  1410 , then protection checks can continue as may be performed for any secure access except the UV-secure-domain-register (setup by the secure control interface before making a secure-UV access) can be used as the specified secure domain for the domain check at block  1420  where processing continues. In addition, any violation that is detected (entry point D) for a UV access at block  1425  can be presented as an error at block  1430  rather than an exception to the hypervisor at block  1435  as is done for a secure guest violation at block  1425  (Secure-UV=No). 
     For access that are not tagged as secure-UV accesses at block  1405 , the hardware determines if the access is a secure guest access at block  1440 , and if not, and if the page is marked as secure at block  1445 , an exception can be presented to the hypervisor at block  1435 . Otherwise, if the access is not a secure guest access at block  1440  and the page is not marked as secure at block  1445 , then translation is successful at block  1450 . 
     If the access is a secure guest access at block  1440  or a secure-UV access to storage registered as secure-UV storage at block  1410 , the hardware can check to make sure the storage is registered to the secure entity associated with the access at block  1420 . If this is a secure-UV access, the specified secure-domain can be obtained from the UV-secure-domain register (loaded by the secure control interface based on secure-UV storage being accessed) and for a secure-guest access, the specified secure-domain is obtained from the SG-secure-domain register (loaded when the secure entity is dispatched). If the storage being accessed is not registered to the specified secure-domain at block  1420 , then for secure-UV accesses at block  1425  an error is taken at block  1430  and for secure-guest accesses at block  1425  (secure-UV=No) an exception is presented to the hypervisor at block  1435 . 
     For secure accesses to storage at block  1440  and block  1410  that are registered to the specified secure-domain at block  1420 , if the virtual address check is disabled, i.e., the DA-bit=1 at block  1455  and the access is real at block  1460 , then translation is complete at block  1450 . If, however, the DA-bit=1 at block  1455  but the access is virtual at block  1460  (real=No), then for secure-UV accesses at block  1425  an error is taken at block  1430  and for secure-guest accesses at block  1425  (secure-UV=No) an exception is presented to the hypervisor at block  1435 . If the DA-bit=0 at block  1455  and the access is a virtual access at block  1475 , then the hardware can determine if the host virtual to host absolute mapping of the access matches that registered for this host absolute address at block  1470 . If so, then translation completes successfully at block  1450 . If the mapping does not match at block  1470 , then for secure-UV accesses at block  1425  an error is taken at block  1430  and for secure-guest accesses at block  1425  (secure-UV=No) an exception is presented to the hypervisor at block  1435 . If the DA-bit=0 and the access is a real access at block  1475  (virtual=No) then for secure-UV accesses at block  1425  an error is taken at block  1430  and for secure-guest accesses at block  1425  (secure-UV=No) an exception is presented to the hypervisor at block  1435 ; alternately, the translation may complete successfully at block  1450 . Any access by the I/O subsystem at block  1480  can check to see if the page is marked as secure at block  1445  and if the page is secure, an exception can be presented to the hypervisor at block  1435 ; if the page is not marked as secure, the translation is successful at block  1450 . 
     Various checks of storage registration and mapping can be managed collectively through zone security table interface  1485 . For example, blocks  1410 ,  1420 ,  1455 ,  1470 , and  1475  can interface with a zone security table that is associated with a same zone to manage various accesses. 
       FIG. 15  depicts a system  1500  according to one or more embodiments of the present invention. The system  1500 , which can be any computing device as described herein, includes a hardware  1501  supporting a processor  1502 , a system memory  1503 , and a secure interface control  1530 . Operating on the hardware  1501  is a logical partition hypervisor  1510  that supports one or more untrusted entities (e.g., hypervisors; represented by untrusted entities  1521  and  1522 ). The untrusted (e.g., un-secured) entity  1521  supports one or more secured entities (e.g., guests) (represented by a secured entity  1541   a . 0  through a secured entity  1541   a .n, where n is an integer greater than 0). Similarly, the untrusted entity  1522  supports one or more secured entities (represented by a secured entity  1542   a . 0  through a secured entity  1542   a .n, where n is an integer greater than 0). Any of the hypervisors  1521  and  1522  and/or secured entities  1541  and  1542  can make a call (e.g., an instruction call) to the secure interface control  1530 . The hypervisors  1521  and  1522  and/or secured entities  1541  and  1542 , can be considered software of the system  1500  that are in communication with the secure interface control  1530 . In the context of this patent, the hypervisor being described corresponds to untrusted entities  1521  and  1522  and may also be referred to as the host or the operating system (OS). The LPAR hypervisor  1510  is part of trusted firmware although it is not necessarily a part of the secure interface control. The secured entity  1541  and  1542  may also be referred to as the guest, virtual machine (VM) or container. 
     As noted herein, the secure interface control  1530  provides a secure interface between the hypervisors  1521  and  1522  and the secured entities  1541  and  1542  by working in collaboration with the hardware  1501  and millicode  1570  to provide additional security. As shown, the secure interface control  1530  is implemented in internal, secure, and trusted hardware and/or firmware (e.g., resident on the hardware  1501  between software of the system  1500  and the hardware  1501 ) to provide the initialization and maintenance of a secure environment, as well as the coordination of the dispatch of these secure entities on the hardware  1501 . That is, the secure interface control  1530  runs as a trusted part of the lowest levels of firmware so that each single secured entities  1541  and  1542  can use a distinct portion of data secure storage, as strictly enforced by the hardware  1501 . 
     Many of architected base instructions or commands of the machine, such as Move Character Long (MVCL) and Start Interpretive Execution (SIE) are implemented in millicode  1570 . In this context, the millicode  1570 , using a hardware interface (herein referred to as a communication interface  1580 ), acts as an extension to the hardware  1510  providing an implementation for more complex architectural instructions (i.e., a millicoded instruction). This communication interface  1580  is optimized to provide enter and leave “millimode” to implement these millicoded instructions and functions. In accordance with one or more embodiments, the secure interface control  1570 , in turn, leverages this communication interface  1580 , as, many of the newly added functions required by the secure interface control  1530  are implemented in millicode  1570 , such as secure SIE dispatch and UV Call (UVC). Note that there is no “secure interface control mode.” That is, the system  1500  does not enter and exit a secure interface control mode, rather the millicode  1570  performs secure interface control functions as it would other functions in the system  1500 . As a result, there is no transition between running as the secure interface control  1530  and running as “normal” millicode. Therefore, the technical effects and benefits of embodiments herein include that the communication interface  1580  does not include any software context switch or any of the overhead associated with such a content switch. Further, the hardware  1501  maintains the “architected” state of the guest or hypervisor code that is running and keeps it independent from the “temporary” millicode state. For example, the hardware  1501  continues to monitor and maintain interruptions at the architected guest and/or hypervisor level that invoked the secure interface control  1530 . 
     In accordance with one or more embodiments, when a secure entity  1541  or  1542  is dispatched by the un-trusted entity  1521  or  1522 , the SIE entry millicode sets a new indication that a secure entity is running and loads the secure guest state, including the secure domain ID, into the hardware  1501 . The hardware  1501  then uses this state to make the necessary security checks while that secure guest domain is running. 
     Since the millicode  1570  is already trusted firmware, the millicode  1570  is able to access guest facilities, hypervisor facilities and secure interface control facilities “seamlessly” without switching modes. It can also access all of storage (non-secure storage, secure storage associated with a specific secure guest domain and auxiliary-secure storage which is also sometimes associated with a particular secure guest domain). In one or more implementations, the millicode  1570  does so by using expanded hardware facilities that allow it to specify which type of storage it intends to access so that the proper security checks can be done by the hardware  1501 . These checks are done even when the accesses are performed by the secure interface control  1530 . The secure interface control  1530  makes use of these new mechanisms when executing the UVC instruction and when interpreting certain other host or guest instructions and functions (e.g., some of the UVC command invoke the millicode  1570  for any accesses to secure guest or secure-UV storage). 
       FIG. 16  depicts a process flow  1600  for a communication interface  1580  of  FIG. 15  according to one or more embodiments of the present invention. The process flow  1600  depicts an example of using the existing millicode interface (e.g., the communication interface  1580  of  FIG. 15 ), for UVC without a context switch, while the hardware  1501  of  FIG. 15  already maintains two separate contexts (architected and millicode). 
     The process flow  1600  begins at block  1610 , where the system  1500  of  FIG. 15  executes an architected instruction (e.g., MVCL or UVC). The architected instruction can originate from a program or software, such as a secure entity  1541 ,  1542  or the untrusted entity  1521 ,  1522 . At decision block  1620 , the communication interface  1580  determines whether the architected instruction is a millicoded instruction. If the architected instruction is not the millicoded instruction, the process flow  1630  proceeds to block  1640  where the architected instruction is performed directly by the hardware  1501  without any millicode control. Then, the process ends at block  1640 . 
     If the architected instruction is the millicoded instruction, the process flow  1630  proceeds to block  1650  where the communication interface  1580  of  FIG. 15  enters a millimode. Entering the millimode by the  1580  includes when the hardware  1501  is engaged through the communication interface  1580  to perform the millicoded instruction. At block  1660 , the millicode  1570  of  FIG. 15  performs the millicoded instruction. 
     In this regard, the secure interface control  1580  executing in the hardware  1501  of  FIG. 15  receives an architected instruction (e.g., UVC) from the hypervisors  1521  and  1522  and/or the secured entities  1541  and  1542 . At decision block  1620 , the secure interface control  1570  leverages the communication interface  1580  to determine whether the architected instruction is a millicoded instruction. Note that the millicode  1570  is an extension of the hardware that performs functions of the secure interface control when executing the architected instruction. Enhancements have been made to the communication interface  1580  that allow the millicode  1570  to access all of storage including secure storage associated with a specific secure guest domain (e.g., relative to the secure entity  1541 ,  1542  associated with the architected instruction) in a secure execution context. Communication interface enhancements include additional control bits that can be set by the millicode to specify a secure access. Further, when a secure guest is dispatched, the secure interface control executed in millicode can set an indication that a secure guest is running and load a secure guest state into the hardware. This secure dispatch code can easily access both non-secure portions of the guest state and secure portions of the guest state. At block  1670 , the communication interface  1580  of  FIG. 15  exits the millimode. Then, the process ends at block  1640 . In turn, the hardware continues to use the secure guest state (even when not running in millimode) to execute security checks while a secure guest domain associated with the secure guest is running. 
     It is to be understood that although this disclosure includes a detailed description on cloud computing, implementation of the teachings recited herein are not limited to a cloud computing environment. Rather, embodiments of the present invention are capable of being implemented in conjunction with any other type of computing environment now known or later developed. 
     Cloud computing is a model of service delivery for enabling convenient, on-demand network access to a shared pool of configurable computing resources (e.g., networks, network bandwidth, servers, processing, memory, storage, applications, VMs, and services) that can be rapidly provisioned and released with minimal management effort or interaction with a provider of the service. This cloud model may include at least five characteristics, at least three service models, and at least four deployment models. 
     Characteristics are as follows: 
     On-demand self-service: a cloud consumer can unilaterally provision computing capabilities, such as server time and network storage, as needed automatically without requiring human interaction with the service&#39;s provider. 
     Broad network access: capabilities are available over a network and accessed through standard mechanisms that promote use by heterogeneous thin or thick client platforms (e.g., mobile phones, laptops, and PDAs). 
     Resource pooling: the provider&#39;s computing resources are pooled to serve multiple consumers using a multi-tenant model, with different physical and virtual resources dynamically assigned and reassigned according to demand. There is a sense of location independence in that the consumer generally has no control or knowledge over the exact location of the provided resources but may be able to specify location at a higher level of abstraction (e.g., country, state, or datacenter). 
     Rapid elasticity: capabilities can be rapidly and elastically provisioned, in some cases automatically, to quickly scale out and rapidly released to quickly scale in. To the consumer, the capabilities available for provisioning often appear to be unlimited and can be purchased in any quantity at any time. 
     Measured service: cloud systems automatically control and optimize resource use by leveraging a metering capability at some level of abstraction appropriate to the type of service (e.g., storage, processing, bandwidth, and active user accounts). Resource usage can be monitored, controlled, and reported, providing transparency for both the provider and consumer of the utilized service. 
     Service Models are as follows: 
     Software as a Service (SaaS): the capability provided to the consumer is to use the provider&#39;s applications running on a cloud infrastructure. The applications are accessible from various client devices through a thin client interface such as a web browser (e.g., web-based e-mail). The consumer does not manage or control the underlying cloud infrastructure including network, servers, operating systems, storage, or even individual application capabilities, with the possible exception of limited user-specific application configuration settings. 
     Platform as a Service (PaaS): the capability provided to the consumer is to deploy onto the cloud infrastructure consumer-created or acquired applications created using programming languages and tools supported by the provider. The consumer does not manage or control the underlying cloud infrastructure including networks, servers, operating systems, or storage, but has control over the deployed applications and possibly application hosting environment configurations. 
     Infrastructure as a Service (IaaS): the capability provided to the consumer is to provision processing, storage, networks, and other fundamental computing resources where the consumer is able to deploy and run arbitrary software, which can include operating systems and applications. The consumer does not manage or control the underlying cloud infrastructure but has control over operating systems, storage, deployed applications, and possibly limited control of select networking components (e.g., host firewalls). 
     Deployment Models are as follows: 
     Private cloud: the cloud infrastructure is operated solely for an organization. It may be managed by the organization or a third party and may exist on-premises or off-premises. 
     Community cloud: the cloud infrastructure is shared by several organizations and supports a specific community that has shared concerns (e.g., mission, security requirements, policy, and compliance considerations). It may be managed by the organizations or a third party and may exist on-premises or off-premises. 
     Public cloud: the cloud infrastructure is made available to the general public or a large industry group and is owned by an organization selling cloud services. 
     Hybrid cloud: the cloud infrastructure is a composition of two or more clouds (private, community, or public) that remain unique entities but are bound together by standardized or proprietary technology that enables data and application portability (e.g., cloud bursting for load-balancing between clouds). 
     A cloud computing environment is service oriented with a focus on statelessness, low coupling, modularity, and semantic interoperability. At the heart of cloud computing is an infrastructure that includes a network of interconnected nodes. 
     Referring now to  FIG. 17 , illustrative cloud computing environment  50  is depicted. As shown, cloud computing environment  50  includes one or more cloud computing nodes  10  with which local computing devices used by cloud consumers, such as, for example, personal digital assistant (PDA) or cellular telephone  54 A, desktop computer  54 B, laptop computer  54 C, and/or automobile computer system  54 N may communicate. Nodes  10  may communicate with one another. They may be grouped (not shown) physically or virtually, in one or more networks, such as Private, Community, Public, or Hybrid clouds as described hereinabove, or a combination thereof. This allows cloud computing environment  50  to offer infrastructure, platforms and/or software as services for which a cloud consumer does not need to maintain resources on a local computing device. It is understood that the types of computing devices  54 A-N shown in  FIG. 17  are intended to be illustrative only and that computing nodes  10  and cloud computing environment  50  can communicate with any type of computerized device over any type of network and/or network addressable connection (e.g., using a web browser). 
     Referring now to  FIG. 18 , a set of functional abstraction layers provided by cloud computing environment  50  ( FIG. 17 ) is shown. It should be understood in advance that the components, layers, and functions shown in  FIG. 18  are intended to be illustrative only and embodiments of the invention are not limited thereto. As depicted, the following layers and corresponding functions are provided: 
     Hardware and software layer  60  includes hardware and software components. Examples of hardware components include: mainframes  61 ; RISC (Reduced Instruction Set Computer) architecture based servers  62 ; servers  63 ; blade servers  64 ; storage devices  65 ; and networks and networking components  66 . In some embodiments, software components include network application server software  67  and database software  68 . 
     Virtualization layer  70  provides an abstraction layer from which the following examples of virtual entities may be provided: virtual servers  71 ; virtual storage  72 ; virtual networks  73 , including virtual private networks; virtual applications and operating systems  74 ; and virtual clients  75 . 
     In one example, management layer  80  may provide the functions described below. Resource provisioning  81  provides dynamic procurement of computing resources and other resources that are utilized to perform tasks within the cloud computing environment. Metering and Pricing  82  provide cost tracking as resources are utilized within the cloud computing environment, and billing or invoicing for consumption of these resources. In one example, these resources may include application software licenses. Security provides identity verification for cloud consumers and tasks, as well as protection for data and other resources. User portal  83  provides access to the cloud computing environment for consumers and system administrators. Service level management  84  provides cloud computing resource allocation and management such that required service levels are met. Service Level Agreement (SLA) planning and fulfillment  85  provide pre-arrangement for, and procurement of, cloud computing resources for which a future requirement is anticipated in accordance with an SLA. 
     Workloads layer  90  provides examples of functionality for which the cloud computing environment may be utilized. Examples of workloads and functions which may be provided from this layer include: mapping and navigation  91 ; software development and lifecycle management  92 ; virtual classroom education delivery  93 ; data analytics processing  94 ; transaction processing  95 ; and communication interface  96 . It is understood that these are just some examples and that in other embodiments, the layers can include different services. 
     Turning now to  FIG. 19 , a system  1900  is depicted in accordance with one or more embodiments of the present invention. The system  1900  includes an example node  10  (e.g., a hosting node) that is in direct or indirect communication with one or more client devices  20 A- 20 E, such as via a network  165 . The node  10  can be a datacenter or host server, of a cloud-computing provider. The node  10  executes a hypervisor  12 , which facilitates deploying one or more VMs  15  ( 15 A- 15 N). The node  10  further includes a hardware/firmware layer  11  that provides direct support for functions required by the VMs  15 A-N and hypervisor  12  as well as facilitates the hypervisor  12  in providing one or more services to the VMs  15 . In contemporary implementations communication is provided between the hardware/firmware layer  11  and the hypervisor  12 , between the hardware/firmware layer  11  and the VMs  15 , between the hypervisor  12  and the VMs  15 , and between the hypervisor  12  and the VMs  15  via the hardware/firmware layer  11 . In accordance with one or more embodiments, of the present invention, a secure interface control is provided in the hardware/firmware layer  11 , and the direct communication between the hypervisor  12  and the VMs  15  is eliminated. 
     For example, the node  10  can facilitate a client device  20 A to deploy one or more of the VMs  15 A- 15 N. The VMs  15 A- 15 N may be deployed in response to respective requests from distinct client devices  20 A- 20 E. For example, the VM  15 A may be deployed by the client device  20 A, the VM  15 B may be deployed by the client device  20 B, and the VM  15 C may be deployed by the client device  20 C. The node  10  may also facilitate a client to provision a physical server (without running as a VM). The examples described herein embody the provisioning of resources in the node  10  as part of a VM, however the technical solutions described can also be applied to provision the resources as part of a physical server. 
     In an example, the client devices  20 A- 20 E may belong to the same entity, such as a person, a business, a government agency, a department within a company, or any other entity, and the node  10  may be operated as a private cloud of the entity. In this case, the node  10  solely hosts VMs  15 A- 15 N that are deployed by the client devices  20 A- 20 E that belong to the entity. In another example, the client devices  20 A- 20 E may belong to distinct entities. For example, a first entity may own the client device  20 A, while a second entity may own the client device  20 B. In this case, the node  10  may be operated as a public cloud that hosts VMs from different entities. For example, the VMs  15 A- 15 N may be deployed in a shrouded manner in which the VM  15 A does not facilitate access to the VM  15 B. For example, the node  10  may shroud the VMs  15 A- 15 N using an IBM z Systems® Processor Resource/Systems Manager (PRISM) Logical Partition (LPAR) feature. These features, such as PR/SM LPAR provide isolation between partitions, thus facilitating the node  10  to deploy two or more VMs  15 A- 15 N for different entities on the same physical node  10  in different logical partitions. 
     A client device  20 A from the client devices  20 A- 20   e  is a communication apparatus such as a computer, a smartphone, a tablet computer, a desktop computer, a laptop computer, a server computer, or any other communication apparatus that requests deployment of a VM by the hypervisor  12  of the node  10 . The client device  20 A may send a request for receipt by the hypervisor via the network  165 . A VM  15 A, from the VMs  15 A- 15 N is a VM image that the hypervisor  12  deploys in response to a request from the client device  20 A from the client devices  20 A- 20   e . The hypervisor  12  is a VM monitor (VMM), which may be software, firmware, or hardware that creates and runs VMs. The hypervisor  12  facilitates the VM  15 A to use the hardware components of the node  10  to execute programs and/or store data. With the appropriate features and modifications the hypervisor  12  may be IBM z Systems®, Oracle&#39;s VM Server, Citrix&#39;s XenServer, Vmware&#39;s ESX, Microsoft Hyper-V hypervisor, or any other hypervisor. The hypervisor  12  may be a native hypervisor executing on the node  10  directly, or a hosted hypervisor executing on another hypervisor. 
     Turning now to  FIG. 20 , a node  10  for implementing the teachings herein is shown in according to one or more embodiments of the invention. The node  10  can be an electronic, computer framework comprising and/or employing any number and combination of computing device and networks utilizing various communication technologies, as described herein. The node  10  can be easily scalable, extensible, and modular, with the ability to change to different services or reconfigure some features independently of others. 
     In this embodiment, the node  10  has a processor  2001 , which can include one or more central processing units (CPUs)  2001   a ,  2001   b ,  2001   c , etc. The processor  2001 , also referred to as a processing circuit, microprocessor, computing unit, is coupled via a system bus  2002  to a system memory  2003  and various other components. The system memory  2003  includes read only memory (ROM)  2004  and random access memory (RAM)  2005 . The ROM  2004  is coupled to the system bus  2002  and may include a basic input/output system (BIOS), which controls certain basic functions of the node  10 . The RAM is read-write memory coupled to the system bus  2002  for use by the processor  2001 . 
     The node  10  of  FIG. 20  includes a hard disk  2007 , which is an example of a tangible storage medium readable executable by the processor  2001 . The hard disk  2007  stores software  2008  and data  2009 . The software  2008  is stored as instructions for execution on the node  10  by the processor  2001  (to perform process, such as the processes described with reference to  FIGS. 1-19 . The data  2009  includes a set of values of qualitative or quantitative variables organized in various data structures to support and be used by operations of the software  2008 . 
     The node  10  of  FIG. 20  includes one or more adapters (e.g., hard disk controllers, network adapters, graphics adapters, etc.) that interconnect and support communications between the processor  2001 , the system memory  2003 , the hard disk  2007 , and other components of the node  10  (e.g., peripheral and external devices). In one or more embodiments of the present invention, the one or more adapters can be connected to one or more I/O buses that are connected to the system bus  2002  via an intermediate bus bridge, and the one or more I/O buses can utilize common protocols, such as the Peripheral Component Interconnect (PCI). 
     As shown, the node  10  includes an interface adapter  2020  interconnecting a keyboard  2021 , a mouse  2022 , a speaker  2023 , and a microphone  2024  to the system bus  2002 . The node  10  includes a display adapter  2030  interconnecting the system bus  2002  to a display  2031 . The display adapter  2030  (and/or the processor  2001 ) can include a graphics controller to provide graphics performance, such as a display and management of a GUI  2032 . A communications adapter  2041  interconnects the system bus  2002  with a network  2050  enabling the node  10  to communicate with other systems, devices, data, and software, such as a server  2051  and a database  2052 . In one or more embodiments of the present invention, the operations of the software  2008  and the data  2009  can be implemented on the network  2050  by the server  2051  and the database  2052 . For instance, the network  2050 , the server  2051 , and the database  2052  can combine to provide internal iterations of the software  2008  and the data  2009  as a platform as a service, a software as a service, and/or infrastructure as a service (e.g., as a web application in a distributed system). 
     Embodiments described herein are necessarily rooted in computer technology, and particularly computer servers that host VMs. Further, one or more embodiments of the present invention facilitate an improvement to the operation of computing technology itself, in particular computer servers that host VMs, by facilitating the computer servers that host VMs to host secure VMs, in which even the hypervisor is prohibited from accessing memory, registers, and other such data associated with the secure VM. In addition, one or more embodiments of the present invention provide significant steps towards the improvements of the VM hosting computing servers by using a secure interface control (also referred to herein as an “ultravisor” or “UV”) that includes hardware, firmware (e.g., millicode), or a combination thereof to facilitate a separation of the secure VM and the hypervisor, and thus maintaining a security of the VMs hosted by the computing server. The secure interface control provides lightweight intermediate operations to facilitate the security, without adding substantial overhead to securing VM state during initialization/exit of VMs as described herein. 
     Embodiments of the invention disclosed herein may include system, method, and/or computer program product (herein a system) that implement a communication interface of a secure interface control. Note that, for each of explanation, identifiers for elements are reused for other similar elements of different figures. 
     Various embodiments of the invention are described herein with reference to the related drawings. Alternative embodiments of the invention can be devised without departing from the scope of this invention. Various connections and positional relationships (e.g., over, below, adjacent, etc.) are set forth between elements in the following description and in the drawings. These connections and/or positional relationships, unless specified otherwise, can be direct or indirect, and the present invention is not intended to be limiting in this respect. Accordingly, a coupling of entities can refer to either a direct or an indirect coupling, and a positional relationship between entities can be a direct or indirect positional relationship. Moreover, the various tasks and process steps described herein can be incorporated into a more comprehensive procedure or process having additional steps or functionality not described in detail herein. 
     The following definitions and abbreviations are to be used for the interpretation of the claims and the specification. As used herein, the terms “comprises,” “comprising,” “includes,” “including,” “has,” “having,” “contains” or “containing,” or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a composition, a mixture, process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but can include other elements not expressly listed or inherent to such composition, mixture, process, method, article, or apparatus. 
     Additionally, the term “exemplary” is used herein to mean “serving as an example, instance or illustration.” Any embodiment or design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments or designs. The terms “at least one” and “one or more” may be understood to include any integer number greater than or equal to one, i.e., one, two, three, four, etc. The terms “a plurality” may be understood to include any integer number greater than or equal to two, i.e., two, three, four, five, etc. The term “connection” may include both an indirect “connection” and a direct “connection.” 
     The terms “about,” “substantially,” “approximately,” and variations thereof, are intended to include the degree of error associated with measurement of the particular quantity based upon the equipment available at the time of filing the application. For example, “about” can include a range of ±8% or 5%, or 2% of a given value. 
     The present invention may be a system, a method, and/or a computer program product at any possible technical detail level of integration. The computer program product may include a computer readable storage medium (or media) having computer readable program instructions thereon for causing a processor to carry out aspects of the present invention. 
     The computer readable storage medium can be a tangible device that can retain and store instructions for use by an instruction execution device. The computer readable storage medium may be, for example, but is not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. A non-exhaustive list of more specific examples of the computer readable storage medium includes the following: a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), a static random access memory (SRAM), a portable compact disc read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanically encoded device such as punch-cards or raised structures in a groove having instructions recorded thereon, and any suitable combination of the foregoing. A computer readable storage medium, as used herein, is not to be construed as being transitory signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through a waveguide or other transmission media (e.g., light pulses passing through a fiber-optic cable), or electrical signals transmitted through a wire. 
     Computer readable program instructions described herein can be downloaded to respective computing/processing devices from a computer readable storage medium or to an external computer or external storage device via a network, for example, the Internet, a local area network, a wide area network and/or a wireless network. The network may comprise copper transmission cables, optical transmission fibers, wireless transmission, routers, firewalls, switches, gateway computers and/or edge servers. A network adapter card or network interface in each computing/processing device receives computer readable program instructions from the network and forwards the computer readable program instructions for storage in a computer readable storage medium within the respective computing/processing device. 
     Computer readable program instructions for carrying out operations of the present invention may be assembler instructions, instruction-set-architecture (ISA) instructions, machine instructions, machine dependent instructions, microcode, firmware instructions, state-setting data, configuration data for integrated circuitry, or either source code or object code written in any combination of one or more programming languages, including an object oriented programming language such as Smalltalk, C++, or the like, and procedural programming languages, such as the “C” programming language or similar programming languages. The computer readable program instructions may execute entirely on the user&#39;s computer, partly on the user&#39;s computer, as a stand-alone software package, partly on the user&#39;s computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user&#39;s computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider). In some embodiments, electronic circuitry including, for example, programmable logic circuitry, field-programmable gate arrays (FPGA), or programmable logic arrays (PLA) may execute the computer readable program instructions by utilizing state information of the computer readable program instructions to personalize the electronic circuitry, in order to perform aspects of the present invention. 
     Aspects of the present invention are described herein with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer readable program instructions. 
     These computer readable program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. These computer readable program instructions may also be stored in a computer readable storage medium that can direct a computer, a programmable data processing apparatus, and/or other devices to function in a particular manner, such that the computer readable storage medium having instructions stored therein comprises an article of manufacture including instructions which implement aspects of the function/act specified in the flowchart and/or block diagram block or blocks. 
     The computer readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other device to cause a series of operational steps to be performed on the computer, other programmable apparatus or other device to produce a computer implemented process, such that the instructions which execute on the computer, other programmable apparatus, or other device implement the functions/acts specified in the flowchart and/or block diagram block or blocks. 
     The flowchart and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of instructions, which comprises one or more executable instructions for implementing the specified logical function(s). In some alternative implementations, the functions noted in the blocks may occur out of the order noted in the Figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts or carry out combinations of special purpose hardware and computer instructions. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one more other features, integers, steps, operations, element components, and/or groups thereof. 
     The descriptions of the various embodiments herein have been presented for purposes of illustration, but are not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein was chosen to best explain the principles of the embodiments, the practical application or technical improvement over technologies found in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.