Errata
Specification Update
47
AZ61.
Entry May Fail When Attempting to Set
IA32_DEBUGCTL.FREEZE_WHILE_SMM_EN
Problem:
If bit 14 (FREEZE_WHILE_SMM_EN) is set in the IA32_DEBUGCTL field in the guest-state
area of the VMCS, VM entry may fail as described in Section “VM-Entry Failures During or
After Loading Guest State” of Intel® 64 and IA-32 Architectures Software Developer‟s
Manual Volume 3B: System Programming Guide, Part 2. (The exit reason will be
80000021H and the exit qualification will be zero.) Note that the
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.
AZ62.
VM Entry May Use Wrong Address to Access Virtual-APIC Page
Problem:
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.