34
Specification Update
AAN56.
Performance Monitor Event Offcore_response_0 (B7H) Does Not
Count NT Stores to Local DRAM Correctly
Problem:
When a IA32_PERFEVTSELx MSR is programmed to count the Offcore_response_0
event (Event:B7H), selections in the OFFCORE_RSP_0 MSR (1A6H) determine what is
counted. The following two selections do not provide accurate counts when counting NT
(Non-Temporal) Stores:
• OFFCORE_RSP_0 MSR bit [14] is set to 1 (LOCAL_DRAM) and bit [7] is set to 1
(OTHER): NT Stores to Local DRAM are not counted when they should have been.
• OFFCORE_RSP_0 MSR bit [9] is set to (OTHER_CORE_HIT_SNOOP) and bit [7] is
set to 1 (OTHER): NT Stores to Local DRAM are counted when they should not have
been.
Implication:
The counter for the Offcore_response_0 event may be incorrect for NT stores.
Workaround:
None identified.
Status:
For the steppings affected, see the Summary Tables of Changes.
AAN57.
EFLAGS Discrepancy on Page Faults and on EPT-Induced VM Exits
after a Translation Change
Problem:
This erratum is regarding the case where paging structures are modified to change a
linear address from writable to non-writable without software performing an
appropriate TLB invalidation. When a subsequent access to that address by a specific
instruction (ADD, AND, BTC, BTR, BTS, CMPXCHG, DEC, INC, NEG, NOT, OR, ROL/ROR,
SAL/SAR/SHL/SHR, SHLD, SHRD, SUB, XOR, and XADD) causes a page fault or an EPT-
induced VM exit, the value saved for EFLAGS may incorrectly contain the arithmetic flag
values that the EFLAGS register would have held had the instruction completed without
fault or VM exit. For page faults, this can occur even if the fault causes a VM exit or if
its delivery causes a nested fault.
Implication:
None identified. Although the EFLAGS value saved by an affected event (a page fault or
an EPT-induced VM exit) may contain incorrect arithmetic flag values, Intel has not
identified software that is affected by this erratum. This erratum will have no further
effects once the original instruction is restarted because the instruction will produce the
same results as if it had initially completed without fault or VM exit.
Workaround:
If the handler of the affected events inspects the arithmetic portion of the saved
EFLAGS value, then system software should perform a synchronized paging structure
modification and TLB invalidation.
Status:
For the steppings affected, see the Summary Tables of Changes.
Содержание BX80605I5760
Страница 4: ...Contents 4 Specification Update...
