Abstract:
A method and apparatus for initiating secure operations in a microprocessor system is described. In one embodiment, one initiating logical processor initiates the process by halting the execution of the other logical processors, and then loading initialization and secure virtual machine monitor software into memory. The initiating processor then loads the initialization software into secure memory for authentication and execution. The initialization software then authenticates and registers the secure virtual machine monitor software prior to secure system operations.

Description:
FIELD 
   The present invention relates generally to microprocessor systems, and more specifically to microprocessor systems that may operate in a trusted or secured environment. 
   BACKGROUND 
   The increasing number of financial and personal transactions being performed on local or remote microcomputers has given impetus for the establishment of “trusted” or “secured” microprocessor environments. The problem these environments try to solve is that of loss of privacy, or data being corrupted or abused. Users do not want their private data made public. They also do not want their data altered or used in inappropriate transactions. Examples of these include unintentional release of medical records or electronic theft of funds from an on-line bank or other depository. Similarly, content providers seek to protect digital content (for example, music, other audio, video, or other types of data in general) from being copied without authorization. 
   Existing trusted systems may utilize a complete closed set of trusted software. This method is relatively simple to implement, but has the disadvantage of not allowing the simultaneous use of common, commercially available operating system and application software. This disadvantage limits the acceptance of such a trusted system. 

   
     DESCRIPTION OF THE DRAWINGS 
     The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements and in which: 
       FIG. 1  is a diagram of an exemplary software environment executing in a microprocessor system. 
       FIG. 2  is a diagram of certain exemplary trusted or secured software modules and exemplary system environment, according to one embodiment of the present invention. 
       FIG. 3  is a diagram of an exemplary trusted or secured software environment, according to one embodiment of the present invention. 
       FIG. 4A  is a schematic diagram of an exemplary microprocessor system adapted to support the secured software environment of  FIG. 3 , according to one embodiment of the present invention. 
       FIG. 4B  is a schematic diagram of an exemplary microprocessor system adapted to support the secured software environment of  FIG. 3 , according to an alternate embodiment of the present invention. 
       FIG. 5  is a schematic diagram of an exemplary microprocessor system adapted to support the secured software environment of  FIG. 3 , according to an alternate embodiment of the present invention. 
       FIG. 6  is a time line drawing of the execution of software components, according to one embodiment of the present invention. 
       FIG. 7  is a flowchart of software and other process blocks, according to one embodiment of the present invention. 
   

   DETAILED DESCRIPTION 
   The following description describes techniques for initiating a trusted or secured environment in a microprocessor system. In the following description, numerous specific details such as logic implementations, software module allocation, encryption techniques, bus signaling techniques, and details of operation are set forth in order to provide a more thorough understanding of the present invention. It will be appreciated, however, by one skilled in the art that the invention may be practiced without such specific details. In other instances, control structures, gate level circuits and full software instruction sequences have not been shown in detail in order not to obscure the invention. Those of ordinary skill in the art, with the included descriptions, will be able to implement appropriate functionality without undue experimentation. The invention is disclosed in the form of a microprocessor system. However, the invention may be practiced in other forms of processor such as a digital signal processor, a minicomputer, or a mainframe computer. 
   Referring now to  FIG. 1 , a diagram of an exemplary software environment executing in a microprocessor system is shown. The software shown in  FIG. 1  is not trusted (untrusted). When operating in a high privilege level, the size and constant updating of the operating system  150  make it very difficult to perform any trust analysis in a timely manner. Much of the operating system sits within privilege ring zero ( 0 ), the highest level of privilege. The applications  152 ,  154 , and  156  have much reduced privilege and typically reside within privilege ring three ( 3 ). The existence of the differing privilege rings and the separation of the operating system  150  and applications  152 ,  154  and  156  into these differing privileged rings would appear to allow operating of the software of  FIG. 1  in a trusted mode, based on making a decision to trust the facilities provided by the operating system  150 . However, in practice making such a trust decision is often impractical. Factors that contribute to this problem include the size (number of lines of code) of the operating system  150 , the fact that the operating system  150  may be the recipient of numerous updates (new code modules and patches) and the fact that the operating system  150  may also contain code modules such as device drivers supplied by parties other than the operating system developer. Operating system  150  may be a common one such as Microsoft® Windows®, Linux, or Solaris®, or may be any other appropriate known or otherwise available operating system. The particular types or names of applications or operating systems run or running are not critical. 
   Referring now to  FIG. 2 , a diagram of certain exemplary trusted or secured software modules and exemplary system environment  200  is shown, according to one embodiment of the present invention. In the  FIG. 2  embodiment, processor  202 , processor  212 , processor  222 , and optional other processors (not shown) are shown as separate hardware entities. In other embodiments, the number of processors may differ, as may the boundary of various components and functional units. In some embodiments the processors may be replaced by separate hardware execution threads or “logical processors” running on one or more physical processors. 
   Processors  202 ,  212 ,  222  may contain certain special circuits or logic elements to support secure or trusted operations. For example, processor  202  may contain secure enter (SENTER) logic  204  to support the execution of special SENTER instructions that may initiate trusted operations. Processor  202  may also contain bus message logic  206  to support special bus messages on system bus  230  in support of special SENTER operations. In alternate embodiments, memory control functions of chipset  240  may be allocated to circuits within the processors, and for multiple processors may be included on a single die. In these embodiments, special bus messages may also be sent on busses internal to the processors. The use of special bus messages may increase the security or trustability of the system for several reasons. Circuit elements such as processors  202 ,  212 , and  222  or chipset  240  may only issue or respond to such messages if they contain the appropriate logic elements of embodiments of the present disclosure. Therefore successful exchange of the special bus messages may help ensure proper system configuration. Special bus messages may also permit activities that should normally be prohibited, such as resetting a platform configuration register  278 . The ability of potentially hostile untrusted code to spy on certain bus transactions may be curtailed by allowing special bus messages to be issued only in response to special security instructions. 
   Additionally, processor  202  may contain secure memory  208  to support secure initialization operations. In one embodiment secure memory  208  may be an internal cache of processor  202 , perhaps operating in a special mode. In alternate embodiments secure memory  208  may be special memory. Other processors such as processor  212  and processor  222  may also include SENTER logic  214 ,  224 , bus message logic  216 ,  226 , and secure memory  218 ,  228 . 
   A “chipset” may be defined as a group of circuits and logic that support memory and input/output (I/O) operations for a connected processor or processors. Individual elements of a chipset may be grouped together on a single chip, a pair of chips, or dispersed among multiple chips, including processors. In the  FIG. 2  embodiment, chipset  240  may include circuitry and logic to support memory and I/O operations to support processors  202 ,  212 , and  222 . In one embodiment, chipset  240  may interface with a number of memory pages  250  through  262  and a device-access page table  248  containing control information indicating whether non-processor devices may access the memory pages  250  through  262 . Chipset  240  may include device-access logic  247  that may permit or deny direct memory access (DMA) from I/O devices to selected portions of the memory pages  250  through  262 . In some embodiment the device access logic  247  may contain all relevant information required to permit or deny such accesses. In other embodiments, the device access logic  247  may access such information held in the device access page table  248 . The actual number of memory pages is not important and will change depending upon system requirements. In other embodiments the memory access functions may be external to chipset  240 . The functions of chipset  240  may further be allocated among one or more physical devices in alternate embodiments. 
   Chipset  240  may additionally include its own bus message logic  242  to support special bus messages on system bus  230  in support of special SENTER operations. Some of these special bus messages may include transferring the contents of a key register  244  to a processor  202 ,  212 , or  222 , or permitting a special ALL_JOINED flag  274  to be examined by a processor  202 ,  212 , or  222 . Additional features of the bus message logic  242  may be to register bus activity by processors in an “EXISTS” register  272  and store certain special bus message activity by processors in a “JOINS” register  272 . Equality of contents of EXISTS register  272  and JOINS register  272  may be used to set the special ALL_JOINED flag  274  to indicate all processors in the system are participating in the secure enter process. 
   Chipset  240  may support standard I/O operations on I/O busses such as peripheral component interconnect (PCI), accelerated graphics port (AGP), universal serial bus (USB), low pin count (LPC) bus, or any other kind of I/O bus (not shown). An interface  290  may be used to connect chipset  240  with token  276 , containing one or more platform configuration registers (PCR)  278 ,  279 . In one embodiment, interface  290  may be the LPC bus (Low Pin Count (LPC) Interface Specification, Intel Corporation, rev. 1.0, 29 Dec. 1997) modified with the addition of certain security enhancements. One example of such a security enhancement would be a locality confirming message, utilizing a previously-reserved message header and address information targeting a platform configuration register (PCR)  278  within token  276 . In one embodiment, token  276  may contain special security features, and in one embodiment may include the trusted platform module (TPM)  281  disclosed in the Trusted Computing Platform Alliance (TCPA) Main Specification, version 1.1a, 1 Dec. 2001, issued by the TCPA (available at the time of filing of the present application at www.trustedpc.com). 
   Two software components identified in system environment  200  are a Secure Virtual Machine Monitor (SVMM)  282  module and a Secure Initialization Authenticated Code (SINIT-AC)  280  module. The SVMM  282  module may be stored on a system disk or other mass storage, and moved or copied to other locations as necessary. In one embodiment, prior to beginning the secure launch process SVMM  282  may be moved or copied to one or more memory pages  250  through  262 . Following the secure enter process, a virtual machine environment may be created in which the SVMM  282  may operate as the most privileged code within the system, and may be used to permit or deny direct access to certain system resources by the operating system or applications within the created virtual machines. 
   Some of the actions required by the secure enter process may be beyond the scope of simple hardware implementations, and may instead advantageously use a software module whose execution can be implicitly trusted. In one embodiment, these actions may be performed by Secure Initialization (SINIT) code. Three exemplary actions are identified here, but these actions should not be taken to be limiting. One action may require that various controls representing critical portions of the system configuration be tested to ensure that the configuration supports the correct instantiation of the secure environment. In one embodiment, one required test may be that the memory controller configuration provided by chipset  240  does not permit two or more different system bus addresses to touch the same location within memory pages  250  through  262 . A second action may be to configure the device-access page table  248  and device-access logic  247  to protect those memory pages used by the memory-resident copy of SVMM  282  from interference by non-processor devices. A third action may be to calculate and register the SVMM  282  module&#39;s identity and transfer system control to it. Here “register” means placing a trust measurement of SVMM  282  into a register, for example into PCR  278  or into PCR  279 . When this last action is taken, the trustworthiness of the SVMM  282  may be inspected by a potential system user. 
   The SINIT code may be produced by the manufacturer of the processors or of the chipsets. For this reason, the SINIT code may be trusted to aid in the secure launch of chipset  240 . In order to distribute the SINIT code, in one embodiment a well-known cryptographic hash is made of the entire SINIT code, producing a value known as a “digest”. One embodiment produces a 160-bit value for the digest. The digest may then be encrypted by a private key, held in one embodiment by the manufacturer of the processor, to form a digital signature. When the SINIT code is bundled with the corresponding digital signature, the combination may be referred to as SINIT authenticated code (SINIT-AC)  280 . Copies of the SINIT-AC  280  may be later validated as discussed below. 
   The SINIT-AC  280  may be stored on system disk or other mass storage or in a fixed media, and moved or copied to other locations as necessary. In one embodiment, prior to beginning the secure launch process SINIT-AC  280  may be moved or copied into memory pages  250 - 262  to form a memory-resident copy of SINIT-AC. 
   Any logical processor may initiate the secure launch process, and may then be referred to as the initiating logical processor (ILP). In the present example processor  202  becomes the ILP, although any of the processors on system bus  230  could become the ILP. Neither memory-resident copy of SINIT-AC  280  nor memory-resident copy of SVMM  282  may be considered trustworthy at this time since, among other reasons, the other processors or the DMA devices may overwrite memory pages  250 - 262 . 
   The ILP (processor  202 ) then executes a special instruction. This special instruction may be referred to as a secured enter (SENTER) instruction, and may be supported by SENTER logic  204 . Execution of the SENTER instruction may cause the ILP (processor  202 ) to issue special bus messages on system bus  230 , and then wait considerable time intervals for subsequent system actions. After execution of SENTER begins, one of these special bus messages, SENTER BUS MESSAGE, is broadcast on system bus  230 . Those logical processors other than the ILP, which may be referred to as responding logical processors (RLPs), respond to the SENTER BUS MESSAGE with an internal non-maskable event. In the present example, the RLPs include processor  212  and processor  222 . The RLPs must each terminate current operations, send a RLP acknowledge (ACK) special bus message on system bus  230 , and then enter a wait state. It should be noted that the ILP also sends its own ACK message over system bus  230 . 
   The chipset  240  may contain a pair of registers, “EXISTS” register  270  and “JOINS” register  272 . These registers may be used to verify that the ILP and all of the RLPs are responding properly to the SENTER BUS MESSAGE. In one embodiment, chipset  240  may keep track of all operational logical processors in the system by writing a “1” into the corresponding bit of the EXISTS register  270  on any system bus transaction made by that logical processor. In this embodiment, each transaction on system bus  230  must contain an identification field containing the logical processor identifier. In one embodiment, this consists of a physical processor identifier and an indentifier for the hardware execution thread within each physical processor. For example, if a thread executing on processor  222  caused any bus transactions on system bus  230 , chipset  240  would see this logical processor identifier within the transaction and write a “1” into the corresponding location  286  within EXISTS register  270 . During the secure launch process, when that same thread on processor  222  sends its ACK message on system bus  230 , the chipset  240  would also see this and could write a “1” into the corresponding location  288  in the JOINS register  272 . (In the  FIG. 2  example, each physical processor is shown with only a single thread executing for clarity. In alternate embodiments the physical processors may support multiple threads, and thereby multiple logical processors.) When the contents of the JOINS register  272  matches the contents of the EXISTS register  270 , then chipset  240  can set an ALL_JOINED flag  246  indicating that all processors have properly responded to the SENTER BUS MESSAGE. 
   In another embodiment, EXISTS register  270  and JOINS register  272  may continue to aid security subsequent to the setting of the ALL_JOINED flag  246 . During the time subsequent to the setting of the ALL_JOINED flag  246  until the end of trusted or secure operations, chipset  240  may continue to monitor and compare bus cycles against the JOINS register  272 . During this period, if chipset  240  ever sees a bus transaction from a logical processor that is not currently identified in JOINS register  272 , then chipset  240  may presume that this logical processor has somehow “appeared” late. This would imply that such a logical processor did not participate in the secure launch process, and therefore could represent an attacker (security threat). In such circumstances, chipset  240  may respond appropriately to keep this attacker out of the secured environment. In one embodiment, chipset  240  may force a system reset in such circumstances. In a second embodiment, similar detection of a “late” processor may be achieved by each logical processor asserting a special reserved signal on the system bus on every transaction following the assertion of the ACK bus message. In this embodiment, following the setting of the ALL_JOINED flag  246  if the chipset  240  observes a bus transaction initiated by a processor without the special signal asserted, then chipset  240  may again presume that this logical processor has somehow appeared “late”, and may represent an attacker. 
   After issuing the SENTER BUS MESSAGE, the ILP (processor  202 ) polls the ALL_JOINED flag  246  to see when and if all processors have properly responded with their ACKs. If the flag  246  is never set, several implementations are possible. A watchdog timer in the ILP or chipset or elsewhere may cause a system reset. Alternatively, the system may hang requiring operator reset. In either case the assertion of a secure environment is protected (in that the secure launch process does not complete unless all processors participate), although the system may not continue to function. In normal operations, after a short time the ALL_JOINED flag  246  is set, and the ILP may be assured that all other logical processors have entered a wait state. 
   When the ALL_JOINED flag  246  is set, the ILP (processor  202 ) may move both a copy of SINIT-AC  280  and key  284  into secure memory  208  for the purpose of authenticating and subsequently executing the SINIT code included in SINIT-AC  280 . In one embodiment, this secure memory  208  may be an internal cache of the ILP (processor  202 ), perhaps operating in a special mode. Key  284  represents the public key corresponding to the private key used to encrypt the digital signature included in the SINIT-AC  280  module, and is used to verify the digital signature and thereby authenticate the SINIT code. In one embodiment, key  284  may already be stored in the processor, perhaps as part of the SENTER logic  204 . In another embodiment, key  284  may be stored in a read-only key register  244  of chipset  240 , which is read by the ILP. In yet another embodiment, either the processor or the chipset&#39;s key register  244  may actually hold a cryptographic digest of key  284 , where key  284  itself is included in the SINIT-AC  280  module. In this last embodiment, the ILP reads the digest from key register  244 , calculates an equivalent cryptographic hash over the key  284  embedded in SINIT-AC  280 , and compares the two digests to ensure the supplied key  284  is indeed trusted. 
   A copy of SINIT-AC and a copy of a public key may then exist within secure memory  208 . The ILP may now validate the copy of SINIT-AC by decrypting the digital signature included in the copy of the SINIT-AC using the copy of a public key. This decryption produces an original copy of a cryptographic hash&#39;s digest. If a newly-calculated digest matches this original digest then the copy of SINIT-AC and its included SINIT code may be considered trustable. 
   The ILP may now issue another special bus message, SENTER CONTINUE MESSAGE, via system bus  230  signaling the waiting RLP&#39;s (processor  212 , processor  222 ) and chipset  240  that secured operations are going to be initiated. The ILP may now register the unique identity of the SINIT-AC module by writing the SINIT-AC module&#39;s cryptographic digest value to a platform configuration register  272  in the security token  276 , as outlined below. The ILP&#39;s execution of its SENTER instruction may now terminate by transferring execution control to the trusted copy of the SINIT code held within the ILP&#39;s secure memory  208 . The trusted SINIT code may then perform its system test and configuration actions and may register the memory-resident copy of SVMM, in accordance with the definition of “register” above. 
   Registration of the memory-resident copy of SVMM may be performed in several manners. In one embodiment, the SENTER instruction running on the ILP writes the calculated digest of SINIT-AC into PCR  278  within the security token  276 . Subsequently, the trusted SINIT code may write the calculated digest of the memory-resident SVMM to the same PCR  278  or another PCR  279  within the security token  276 . If the SVMM digest is written to the same PCR  278 , the security token  276  hashes the original contents (SINIT digest) with the new value (SVMM digest) and writes the result back into the PCR  278 . In embodiments where the first (initializing) write to PCR  278  is limited to the SENTER instruction, the resulting digest may be used as a root of trust for the system. 
   Once the trusted SINIT code has completed its execution, and has registered the identity of the SVMM in a PCR, the SINIT code may transfer ILP execution control to the SVMM. In a typical embodiment, the first SVMM instructions executed by the ILP may represent a self-initialization routine for the SVMM. The ILP may in one embodiment issue individual RLP JOIN MESSAGE special bus messages to each RLP, causing each of the RLPs to join in operations under the supervision of the now-executing copy of SVMM. From this point onwards, the overall system is operating in trusted mode as outlined in the discussion of  FIG. 3  below. 
   Referring now to  FIG. 3 , a diagram of an exemplary trusted or secured software environment is shown, according to one embodiment of the present invention. In the  FIG. 3  embodiment, trusted and untrusted software may be loaded simultaneously and may execute simultaneously on a single computer system. A SVMM  350  selectively permits or prevents direct access to hardware resources  380  from one or more untrusted operating systems  340  and untrusted applications  310  through  330 . In this context, “untrusted” does not necessarily mean that the operating system or applications are deliberately misbehaving, but that the size and variety of interacting code makes it impractical to reliably assert that the software is behaving as desired, and that there are no viruses or other foreign code interfering with its execution. In a typical embodiment, the untrusted code might consist of the normal operating system and applications found on today&#39;s personal computers. 
   SVMM  350  also selectively permits or prevents direct access to hardware resources  380  from one or more trusted or secure kernels  360  and one or more trusted applications  370 . Such a trusted or secure kernel  360  and trusted applications  370  may be limited in size and functionality to aid in the ability to perform trust analysis upon it. The trusted application  370  may be any software code, program, routine, or set of routines which is executable in a secure environment. Thus, the trusted application  370  may be a variety of applications, or code sequences, or may be a relatively small application such as a Java applet. 
   Instructions or operations normally performed by operating system  340  or kernel  360  that could alter system resource protections or privileges may be trapped by SVMM  350 , and selectively permitted, partially permitted, or rejected. As an example, in a typical embodiment, instructions that change the processor&#39;s page table that would normally be performed by operating system  340  or kernel  360  would instead be trapped by SVMM  350 , which would ensure that the request was not attempting to change page privileges outside the domain of its virtual machine. 
   Referring now to  FIG. 4A , one embodiment of a microprocessor system  400  adapted to support the secured software environment of  FIG. 3  is shown. CPU A  410 , CPU B  414 , CPU C  418 , and CPU D  422  may be configured with additional microcode or logic circuitry to support the execution of special instructions. In one embodiment, this additional microcode or logic circuitry may be the SENTER logic  204  of FIG.  2 . These special instructions may support the issuance of special bus messages on system bus  420  that may enable the proper synchronization of the processors while launching the secure environment. In one embodiment, the issuance of special bus messages may be supported by circuitry such as the bus message logic  206  of FIG.  2 . Similarly chipset  430  may be similar to chipset  240  and may support the above-mentioned special cycles on system bus  420 . The number of physical processors may vary upon the implementation of a particular embodiment. In one embodiment, the processors may be Intel® Pentium® class microprocessors. Chipset  430  may interface with mass storage devices such as fixed media  444  or removable media  448  via PCI bus  446 , or, alternately, via USB  442 , an integrated controller electronics (IDE) bus (not shown), a small computer systems interconnect (SCSI) bus (not shown), or any other I/O busses. The fixed media  444  or removable media  448  may be magnetic disks, magnetic tape, magnetic diskettes, magneto-optical drives, CD-ROM, DVD-ROM, Flash memory cards, or many other forms of mass storage. 
   In the  FIG. 4A  embodiment, the four processors CPU A  410 , CPU B  414 , CPU C  418 , and CPU D  422  are shown as four separate hardware entities. In other embodiments, the number of processors may differ. Indeed, the physically discrete processors may be replaced by separate hardware execution threads running on one or more physical processors. In the latter case these threads possess many of the attributes of additional physical processors. In order to have a generic expression to discuss using any mixture of multiple physical processors and multiple threads upon processors, the expression “logical processor” may be used to describe either a physical processor or a thread operating in one or more physical processors. Thus, one single-threaded processor may be considered a logical processor, and multi-threaded or multi-core processors may be considered multiple logical processors. 
   In one embodiment, chipset  430  interfaces with a modified LPC bus  450 . Modified LPC bus  450  may be used to connect chipset  430  with a security token  454 . Token  454  may in one embodiment include the TPM  471  envisioned by the Trusted Computing Platform Alliance (TCPA). 
   Referring now to  FIG. 4B , an alternate embodiment of a microprocessor system  490  adapted to support the secured software environment of  FIG. 3  is shown. Differing from the  FIG. 4A  embodiment, CPU A  410  and CPU B  414  may be connected to chipset  428  with system bus A  402  whereas CPU C  418  and CPU D  422  may be connected to chipset  428  with system bus B  404 . In other embodiments more than two system busses may be utilized. In another alternative embodiment, point-to-point busses may be used. Special instructions may support the issuance of special bus messages on system bus A  402  and system bus B  404  that may enable the proper synchronization of the processors while launching the secure environment. In one embodiment, the issuance of special bus messages may be supported by circuitry such as the bus message logic  206  of FIG.  2 . 
   In one embodiment, chipset  428  is responsible for maintaining consistency and coherency across system bus A  402  and system bus B  404 . If a bus message, standard or special, is sent across system bus A  402 , chipset  428  reflects that message (when appropriate) onto system bus B  404 , and vice-versa. 
   In an alternate embodiment, chipset  428  treats system bus A  402  and system bus B  404  as independent subsystems. Any special bus messages issued on system bus A  402  apply only to processors on that bus: similarly, special bus messages issued on system bus B  404  apply only to processors on that bus. Any protected memory that is established with respect to system bus A  402  is only accessible to processors connected to system bus A  402 , and the processors on system bus B  404  may be treated as untrusted devices. To gain access to any protected memory established for CPU A  410  and CPU B  414  on system bus A  402 , processors CPU C  418  and CPU D  422  on system bus B  404  must perform their own SENTER process, creating a registered environment equal to that created for the processors on system bus A  402 . 
   Referring now to  FIG. 5 , a schematic diagram of an exemplary microprocessor system  500  adapted to support the secured software environment of  FIG. 3  is shown, according to an alternate embodiment of the present invention. Differing from the  FIG. 4A  embodiment, each processor (for example, CPU A  510 ) may include certain chipset functions (for example, chipset functions  593 ) that, for example, perform memory controller functions and device access logic functions. These chipset functions thereby allow the direct connection of memory (for example, memory A  502 ) to the processor. Other chipset functions may remain in a separate chipset  530 . Special bus messages may be issued across system bus  520 . 
   Each processor may make indirect accesses to memory connected to other processors: however, these accesses may be considerably slower when compared to accesses to a processor&#39;s own memory. Prior to the start of the SENTER process, software may move copies of SINIT-AC  566  and SVMM  574  from fixed media  544  into local memory  504 , forming copy of SINIT-AC  556  and copy of SVMM  572 . In one embodiment, the memory  504  may be selected because it is directly accessed by the processor intended to be the ILP, in the  FIG. 5  example this is CPU B  514 . Alternatively, the SINIT-AC  566  and SVMM  574  copies may be placed in other memories attached to other (non-ILP) processors, so long as the ILP  514  has the ability to access those memories. CPU B ILP  514  begins the secure enter process by issuing the SENTER instruction, as already described in  FIG. 2 , and with similar consequences and bus cycles issued. Chipset  530  may utilize EXISTS register  576 , JOINS register  580 , and ALL_JOINED flag  584  as described above in connection with  FIG. 2  to determine whether all processors have properly responded to the SENTER BUS MESSAGE and signal this information to the ILP. The ILP (CPU B  514 ) may again move the memory-resident copy of SINIT-AC  556  into secure memory  560 , along with a copy of a public key  564 . Upon verification and registration of SINIT-AC  556 , ILP may then continue to verification and registration of the memory-resident copy of SVMM  572 . 
   Referring now to  FIG. 6 , a time line drawing of various operations is shown, according to one embodiment of the present invention. The timeline of  FIG. 6  shows the overall schedule of the operations discussed in connection with the exemplary system discussed in connection with  FIG. 2  above. When software decides that secure or trusted operations are desired, at time  610  any software locates and makes a copy of SINIT-AC  280  and SVMM  282  available to a subsequent SENTER instruction. In this example, software loads a copy of SINIT-AC  280  and a copy of SVMM  282  into one or more memory pages  250 - 262 . One processor, in the present example processor  202 , is then selected to be the ILP, which issues the SENTER instruction at time  612 . At time  614  the ILP&#39;s SENTER instruction issues the SENTER BUS MESSAGE  616 . The ILP then issues its own SENTER ACK  608  at time  618  prior to entering a wait-for-chipset-flag state at time  628 . 
   Each RLP, such as processor  222 , respond to the SENTER BUS MESSAGE  616  by completing the current instruction during time  620 . The RLP then issues its SENTER ACK  622  and then enters a state  634  where it waits for an SENTER CONTINUE MESSAGE. 
   The chipset  240  spends time  624  setting the JOINS register  272  responsive to the SENTER ACK messages observed on system bus  230 . When the JOINS register  272  contents matches the EXISTS register  270  contents, chipset  240  sets the ALL_JOINED flag  246  at time  626 . 
   During this time, the ILP may remain in a loop while polling the ALL_JOINED flag  246 . When the ALL_JOINED flag  246  is set, and ILP determines that the ALL_JOINED flag  246  is set at time  630 , the ILP may then issue the SENTER CONTINUE MESSAGE during time  632 . When the SENTER CONTINUE MESSAGE is broadcast on system bus  230  at time  636 , the RLPs may enter a wait-for-join state. For example, the RLP of processor  222  enters a wait-for-join state during time period  638 . 
   Upon issuing the SENTER CONTINUE MESSAGE, the ILP may then (in time period  640 ) bring the public key of key register  244  of chipset  240  and a copy of SINIT-AC into its secure memory  208  to form a copy of the key and a copy of SINIT-AC. In another embodiment, key register  244  may contain a digest of the public key, and the actual public key may be included in, or with, the SINIT-AC. Upon authenticating the copy of SINIT-AC as described above in connection with  FIG. 2 , the ILP may then actually execute the copy of SINIT-AC within secure memory  208 . 
   After the copy of SINIT-AC within secure memory  208  begins execution, it then (during time period  640 ) validates and registers the memory-resident copy of SVMM. After the copy of SVMM is registered in the PCR  278  of security token  276 , the memory-resident copy of SVMM itself begins execution. At this time, during ongoing time period  650 , SVMM operations are established in the ILP. 
   Among the first things that the ILP SVMM operation does is issue individual RLP JOIN MESSAGES on the system bus  230 . An example is a processor  222  JOIN MESSAGE  644 . This message may include a location in memory at which the RLP processor  222  may join in execution of the registered memory-resident copy of SVMM. Alternatively, the ILP SVMM operations may have registered a memory location in a predetermined location in the chipset or memory, and upon receiving the JOIN MESSAGE the RLP retrieves its starting address from this location. After receiving the processor  222  JOIN MESSAGE, and determining its starting address, during time period  646  the RLP processor  222  jumps to this location and joins execution of the registered memory-resident copy of the SVMM. 
   After all the RLPs have joined the registered memory-resident copy of the SVMM, secured operations are established throughout the microcomputer system  200 . 
   Referring now to  FIG. 7 , a flowchart of software and other process blocks is shown, according to one embodiment of the present invention. For the sake of clarity  FIG. 7  only shows process blocks for a single representative RLP. In other embodiments there may be several responding logical processors. 
   The process  700  begins at block  710  when a logical processor makes a copy of the SINIT-AC and SVMM modules available for access by a subsequent SENTER instruction. In this example, in block  712  the ILP loads the SINIT-AC and SVMM code from mass storage into physical memory. In alternative embodiments, any logical processor may do so, not just the ILP. A processor becomes the ILP by executing the SENTER instruction, as identified in block  714 . In block  716 , the ILP SENTER instruction issues an SENTER BUS MESSAGE in block  716 . The ILP then, in block  718 , issues its own SENTER ACK message to the chipset. The ILP then enters a wait state, shown as decision block  720 , and waits for the chipset to set its ALL_JOINED flag. 
   After each RLP receives the SENTER BUS MESSAGE in block  770 , it halts execution with the end of the current instruction, and then in block  772  issues its own SENTER ACK. Each RLP then enters a wait state, shown as decision block  774 , and waits for a SENTER CONTINUE MESSAGE to arrive from the ILP. 
   The chipset sets the corresponding bits in the JOINS register when SENTER ACK messages are received. When the JOINS register contents equals the EXISTS register contents, the chipset sets its ALL_JOINED flag, signaling the ILP to proceed from decision block  720 . 
   The ILP, upon exiting decision block  720  on the YES path, then issues a SENTER CONTINUE MESSAGE in block  722 . This signals each RLP to proceed from decision block  774 . Each RLP then enters a second wait state, shown as decision block  776 , and waits for a SENTER JOIN MESSAGE. 
   Meanwhile the ILP, in block  724 , moves the public key of the chipset and the memory-resident copy of SINIT-AC into its own secure memory for secure execution. The ILP, in block  726 , uses the key to validate the secure-memory-resident copy of SINIT-AC, and then executes it. The execution of SINIT-AC may perform tests of the system configuration and the SVMM copy, then registers the SVMM identity, and finally begins the execution of SVMM in block  728 . As part of actions performed in block  728 , the ILP SINIT code may configure device-access page table  248  and device-access logic  247  of memory and chipset to protect those memory pages used by the memoryresident copy of SVMM  282  from interference by non-processor devices, as shown in block  754 . 
   After the ILP begins execution under the control of SVMM, in block  730  the ILP sends an individual SENTER JOIN MESSAGE to each RLP. After issuing the SENTER JOIN MESSAGE, the ILP then in block  732  begins SVMM operations. 
   The receipt of the SENTER JOIN MESSAGE causes each RLP to leave the wait state represented by decision block  776  along the YES path, and begin SVMM operations in block  780 . The SENTER JOIN MESSAGE may contain the SVMM entry point the RLP branch to when joining SVMM operations. Alternatively, the ILP SVMM code may register the appropriate RLP entry point in a system location (for example, in the chipset), to be retrieved by the RLP upon receipt of the SENTER JOIN MESSAGE. 
   While various embodiments disclosed include two or more processors (either logical or physical processors), it should be understood that such multi-processor and/or multi-threaded systems are described in more detail to explain the added complexity associated with securing a system with multiple logical or physical processors. An embodiment also likely to be advantageous in less complex system may use only one processor. In some cases, the one physical processor may be multi-threading and therefore may include multiple logical processors (and accordingly have an ILP and an RLP as described). In other cases, however, a single-processor, single-threaded system may be used, and still utilize disclosed secure processing techniques. In such cases, there may be no RLP; however, the secure processing techniques still operate to reduce the likelihood that data can be stolen or manipulated in an unauthorized manner. 
   In the foregoing specification, the invention has been described with reference to specific exemplary embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention as set forth in the appended claims. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.