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BJ100.
Use of VMASKMOV to Access Memory Mapped I/O or Uncached
Memory May Cause The Logical Processor to Hang
Problem:
Under a complex set of conditions, using VMASKMOV to reference memory mapped I/O
or uncached memory may cause the logical processor to hang.
Implication:
Due to this erratum, the logical processor may hang. Intel's Software Developers
Manual states "VMASKMOV should not be used to access memory mapped I/O and un-
cached memory as the access and the ordering of the individual loads or stores it does
is implementation specific." Intel has not observed this erratum with 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.
BJ101.
PEBS May Unexpectedly Signal a PMI After The PEBS Buffer is Full
Problem:
The Software Developer's Manual states that no PMI should be generated when PEBS
index reaches PEBS Absolute Maximum. Due to this erratum a PMI may be generated
even though the PEBS buffer is full.
Implication:
PEBS may trigger a PMI even though the PEBS index has reached the PEBS Absolute
Maximum.
Workaround:
None identified.
Status:
For the steppings affected, see the Summary Tables of Changes.
BJ102.
XSAVEOPT May Fail to Save Some State after Transitions Into or Out
of STM
Problem:
The XSAVEOPT instruction may optimize performance by not saving state that has not
been modified since the last execution of XRSTOR. This optimization should occur only
if the executions of XSAVEOPT and XRSTOR are either both or neither in SMM (system-
management mode). Due to this erratum, this optimization may be performed by the
first execution of XSAVEOPT after a transition into or out of the STM (SMM-transfer
monitor) if the most recent execution of XRSTOR occurred before that transition. For
transitions into the STM, the erratum applies only to transitions using the VMCALL
instruction. This erratum can occur only if the two executions are at the same privilege
level, use the same linear address, and are either both or neither in VMX non-root
operation. The erratum does not apply if software in SMM never uses XRSTOR or
XSAVEOPT.
Implication:
This erratum may lead to unpredictable system behavior.
Workaround:
STM software should execute the XRSTOR instruction with the value 0 in EDX:EAX after
each transition into the STM (after setting CR4.OSXSAVE) and before each transition
out of the STM. Bytes 512 to 575 of the save area used by XRSTOR should be allocated
in memory, but bytes 0 to 511 need not be. Bytes 512 to 535 should all be 0.
Status:
For the steppings affected, see the Summary Tables of Changes.
Specification Update
51
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