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45.
Speculative Page Fault May Cause Livelock
Problem:
If the processor detects a page fault which is corrected before the operating system
page fault handler can be called e.g., DMA activity modifies the page tables and the
corrected page tables are left in a non-accessed or not dirty state, the processor may
livelock. Intel has not been able to reproduce this erratum with commercial software.
Implication: Should this erratum be encountered the processor will livelock resulting in a system
hang or operating system failure.
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.
46.
PAT Index MSB May Be Calculated Incorrectly
Problem:
When Mode B or Mode C paging support is enabled and all of the following events
occur:
• A page walk occurs that returns a large page from memory, and
• A second page walk occurs that hits an internal processor cache for a 4k page
and the Page Attribute Table (PAT) upper index bit in the Page Table Entry for
this page is set to 1b.
It is possible that the PAT upper index bit in the PTE for this 4k page is incorrectly
ignored and assumed to be 0b. The result is that the memory type in the PAT that
should have come from the corresponding PAT index [4-7] incorrectly comes from
PAT index [0-3].
Implication: If an operating system has programmed the PAT in an asymmetrical fashion i.e. PAT
[0-3] is different from PAT [4-7] then an incorrect memory type may be used.
Workaround:
None identified.
Status:
For the steppings affected, see the Summary Tables of Changes.
47.
SQRTPD and SQRTSD May Return QNaN Indefinite Instead of
Negative Zero
Problem:
When DAZ mode is enabled, and a SQRTPD or SQRTSD instruction has a negative
denormal operand, the instruction will return a QNaN indefinite when the specified
response should be a negative zero.
Implication: When this erratum occurs, the instruction will return a QNaN indefinite when a
negative zero is expected.
Workaround:
Ensure that negative denormals are not used as operands to the SQRTPD or
SQRTSD instructions when DAZ mode is enabled. Software could enable FTZ mode to
ensure that negative denormals are not generated by computation prior to execution
of a SQRTPD or SQRTSD instruction.
Status:
For the steppings affected, see the Summary Tables of Changes.
48
Errata
Specification Update
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