Intel X5472 Specification Update - Page 35

FREEZE_WHILE_SMM_EN bit in the guest IA32_DEBUGCTL field may be set due to a VMWRITE to that field or due to a VM exit that occurs while IA32_DEBUGCTL.FREEZE_WHILE_SMM_EN=1 Implication: A VMM will not be able to properly virtualize a guest using the FREEZE_WHILE_SMM feature. Workaround: It is possible for the BIOS to contain a workaround for this erratum. Alternatively, the following software workaround may be used. If a VMM wants to use the FREEZE_WHILE_SMM feature, it can configure an entry in the VM-entry MSR-load area for the IA32_DEBUGCTL MSR (1D9H); the value in the entry should set the FREEZE_WHILE_SMM_EN bit. In addition, the VMM should use VMWRITE to clear the FREEZE_WHILE_SMM_EN bit in the guest IA32_DEBUGCTL field before every VM entry. (It is necessary to do this before every VM entry because each VM exit will save that bit as 1.) This workaround prevents the VM-entry failure and sets the FREEZE_WHILE_SMM_EN bit in the IA32_DEBUGCTL MSR. Status: For the steppings affected, see the Summary Tables of Changes. AX59. Problem: VM Entry May Use Wrong Address to Access Virtual-APIC Page When XFEATURE_ENABLED_MASK register (XCR0) bit 1 (SSE) is 1, a VM entry executed with the "use TPR shadow" VM-execution control set to 1 may use the wrong address to access data on the virtual-APIC page. Implication: An affected VM entry may exhibit the following behaviors: (1) it may use wrong areas of the virtual-APIC page to determine whether VM entry fails or whether it induces a VM exit due to the TPR threshold; or (2) it may clear wrong areas of the virtual-APIC page. Workaround: It is possible for the BIOS to contain a workaround for this erratum. Status: For the steppings affected, see the Summary Tables of Changes. AX60. Problem: INIT Incorrectly Resets IA32_LSTAR MSR In response to an INIT reset initiated either via the INIT# pin or an IPI (Inter Processor Interrupt), the processor should leave MSR values unchanged. Due to this erratum IA32_LSTAR MSR (C0000082H), which is used by the iA32e SYSCALL instruction, is being cleared by an INIT reset. Implication: If software programs a value in IA32_LSTAR to be used by the SYSCALL instruction and the processor subsequently receives an INIT reset, the SYSCALL instructions will not behave as intended. Intel has not observed this erratum in any commercially available software. Workaround: It is possible for the BIOS to contain a workaround for this erratum. Status: For the steppings affected, see the Summary Tables of Changes. AX61. Problem: CPUID Instruction May Return Incorrect Brand String When a CPUID instruction is executed with EAX = 8000_0002H, 8000_0003H, or 8000_0004H, the returned EAX, EBX, ECX, and/or EDX values may be incorrect. Implication: When this erratum occurs, the processor may report an incorrect brand string. Workaround: It is possible for the BIOS to contain a workaround for this erratum. Status: For the steppings affected, see the Summary Tables of Changes. AX62. Problem: Global Instruction TLB Entries May Not be Invalidated on a VM Exit or VM Entry If a VMM is using global page entries (CR4.PGE is enabled and any present pagedirectories or page-table entries are marked global), then on a VM entry, the instruction TLB (Translation Lookaside Buffer) entries caching global page translations 35 Intel® Xeon® Processor 5400 Series Specification Update