User Guide

Errata
Specification Update 35
KBL044
Execution of VAESENCLAST Instruction May Produce a #NM Exception
Instead of a #UD Exception
Problem
Execution of VAESENCLAST with VEX.L= 1 should signal a #UD (Invalid Opcode)
exception, however, due to the erratum, a #NM (Device Not Available) exception
may be signaled.
Implication
As a result of this erratum, an operating system may restore AVX and other state
unnecessarily.
Workaround None identified.
Status For the steppings affected, see the Summary Table of Changes.
KBL045
Intel® SGX Enclave Accesses to the APIC-Access Page May Cause APIC-
Access VM Exits
Problem
In VMX non-root operation, Intel SGX (Software Guard Extensions) enclave accesses
to the APIC-access page may cause APIC-access VM exits instead of page faults.
Implication
A VMM (virtual-machine monitor) may receive a VM exit due to an access that should
have caused a page fault, which would be handled by the guest OS (operating
system).
Workaround
A VMM avoids this erratum if it does not map any part of the EPC (Enclave Page
Cache) to the guest’s APIC-access address; an operating system avoids this erratum
if it does not attempt indirect enclave accesses to the APIC.
Status For the steppings affected, see the Summary Table of Changes.
KBL046
CR3 Filtering Does Not Compare Bits [11:5] of CR3 and
IA32_RTIT_CR3_MATCH in PAE Paging Mode
Problem
In PAE paging mode, the CR3[11:5] are used to locate the page-directory-pointer
table. Due to this erratum, those bits of CR3 are not compared to
IA32_RTIT_CR3_MATCH (MSR 572H) when IA32_RTIT_CTL.CR3Filter (MSR 570H, bit
7) is set.
Implication
If multiple page-directory-pointer tables are co-located within a 4KB region, CR3
filtering will not be able to distinguish between them so additional processes may be
traced.
Workaround None identified.
Status For the steppings affected, see the Summary Table of Changes.
KBL047 x87 FDP Value May be Saved Incorrectly
Problem
Execution of the FSAVE, FNSAVE, FSTENV, or FNSTENV instructions in real-address
mode or virtual-8086 mode may save an incorrect value for the x87 FDP (FPU data
pointer). This erratum does not apply if the last non-control x87 instruction had an
unmasked exception.
Implication
Software operating in real-address mode or virtual-8086 mode that depends on the
FDP value for non-control x87 instructions without unmasked exceptions may not
operate properly.
Workaround
None identified. Software should use the FDP value saved by the listed instructions
only when the most recent non-control x87 instruction incurred an unmasked
exception.