34
Specification Update
AAU56. 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.
AAU57. 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.
AAU58. Pending x87 FPU Exceptions (#MF) May be Signaled Earlier Than
Expected
Problem: x87 instructions that trigger #MF normally service interrupts before the #MF. Due to
this erratum, if an instruction that triggers #MF is executed while Enhanced Intel
SpeedStep
®
Technology transitions, Intel
®
Turbo Boost Technology transitions, or
Thermal Monitor events occur, the pending #MF may be signaled before pending
interrupts are serviced.
Implication: Software may observe #MF being signaled before pending interrupts are serviced.
Workaround: None identified.
Status: For the steppings affected, see the Summary Tables of Changes.
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