Errata
34 Specification Update
BG47. Performance Monitor Events INSTR_RETIRED and MEM_INST_RETIRED May
Count Inaccurately
Problem: The performance monitor event INSTR_RETIRED (Event C0H) should count the number
of instructions retired, and MEM_INST_ RETIRED (Event 0BH) should count the number
of load or store instructions retired. However, due to this erratum, they may
undercount.
Implication: The performance monitor event INSTR_RETIRED and MEM_INST_RETIRED may reflect
a count lower than the actual number of events.
Workaround:None identified.
Status: For the steppings affected, see the Summary Tables of Changes.
BG48. A Page Fault May Not Be Generated When the PS bit Is Set to “1” in a PML4E
or PDPTE
Problem: On processors supporting Intel 64 architecture, the PS bit (Page Size, Bit 7) is reserved
in PML4Es and PDPTEs. If the translation of the linear address of a memory access
encounters a PML4E or a PDPTE with PS set to 1, a page fault should occur. Due to this
erratum, PS of such an entry is ignored and no page fault will occur due to its being set.
Implication: Software may not operate properly if it relies on the processor to deliver page faults
when reserved bits are set in paging-structure entries.
Workaround:Software should not set Bit 7 in any PML4E or PDPTE that has Present Bit (Bit 0) set to
“1”.
Status: For the steppings affected, see the Summary Tables of Changes.
BG49. BIST Results May Be Additionally Reported after a GETSEC[WAKEUP] or INIT-
SIPI Sequence
Problem: BIST results should only be reported in EAX the first time a logical processor wakes up
from the Wait-For-SIPI state. Due to this erratum, BIST results may be additionally
reported after INIT-SIPI sequences and when waking up RLP's from the SENTER sleep
state using the GETSEC[WAKEUP] command.
Implication: An INIT-SIPI sequence may show a non-zero value in EAX upon wakeup when a zero
value is expected. RLP's waking up for the SENTER sleep state using the
GETSEC[WAKEUP] command may show a different value in EAX upon wakeup than
before going into the SENTER sleep state.
Workaround:If necessary software may save the value in EAX prior to launching into the secure
environment and restore upon wakeup and/or clear EAX after the INIT-SIPI sequence.
Status: For the steppings affected, see the Summary Tables of Changes.
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