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BJ85.
PCMPESTRI, PCMPESTRM, VPCMPESTRI and VPCMPESTRM Always
Operate with 32-bit Length Registers
Problem:
In 64-bit mode, using REX.W=1 with PCMPESTRI and PCMPESTRM or VEX.W=1 with
VPCMPESTRI and VPCMPESTRM should support a 64-bit length operation with RAX/
RDX. Due to this erratum, the length registers are incorrectly interpreted as 32-bit
values.
Implication:
Due to this erratum, using REX.W=1 with PCMPESTRI and PCMPESTRM as well as
VEX.W=1 with VPCMPESTRI and VPCMPESTRM do not result in promotion to 64-bit
length registers.
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.
BJ86.
VM Entries That Return From SMM Using VMLAUNCH May Not Update
The Launch State of the VMCS
Problem:
Successful VM entries using the VMLAUNCH instruction should set the launch state of
the VMCS to "launched". Due to this erratum, such a VM entry may not update the
launch state of the current VMCS if the VM entry is returning from SMM.
Implication:
Subsequent VM entries using the VMRESUME instruction with this VMCS will fail.
RFLAGS.ZF is set to 1 and the value 5 (indicating VMRESUME with non-launched VMCS)
is stored in the VM-instruction error field. This erratum applies only if dual monitor
treatment of SMI and SMM is active.
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.
BJ87.
Interrupt From Local APIC Timer May Not Be Detectable While Being
Delivered
Problem:
If the local-APIC timer's CCR (current-count register) is 0, software should be able to
determine whether a previously generated timer interrupt is being delivered by first
reading the delivery-status bit in the LVT timer register and then reading the bit in the
IRR (interrupt-request register) corresponding to the vector in the LVT timer register. If
both values are read as 0, no timer interrupt should be in the process of being
delivered. Due to this erratum, a timer interrupt may be delivered even if the CCR is 0
and the LVT and IRR bits are read as 0. This can occur only if the DCR (Divide
Configuration Register) is greater than or equal to 4. The erratum does not occur if
software writes zero to the Initial Count Register before reading the LVT and IRR bits.
Implication:
Software that relies on reads of the LVT and IRR bits to determine whether a timer
interrupt is being delivered may not operate properly.
Workaround:
Software that uses the local-APIC timer must be prepared to handle the timer
interrupts, even those that would not be expected based on reading CCR and the LVT
and IRR bits; alternatively, software can avoid the problem by writing zero to the Initial
Count Register before reading the LVT and IRR bits.
Status:
For the steppings affected, see the Summary Tables of Changes.
46
Specification Update
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