Datasheet

Errata
Specification Update 43
AH4. Exception Record (LER) MSRVERW/VERR/LSL/LAR Instructions May
Unexpectedly Update the Last Exception Record (LER) MSR
Problem: The LER MSR may be unexpectedly updated, if the resultant value of the Zero Flag
(ZF) is zero after executing the following instructions.
1. VERR (ZF=0 indicates unsuccessful segment read verification)
2. VERW (ZF=0 indicates unsuccessful segment write verification)
3. LAR (ZF=0 indicates unsuccessful access rights load)
4. LSL (ZF=0 indicates unsuccessful segment limit load)
Implication: The value of the LER MSR may be inaccurate if VERW/VERR/LSL/LAR instructions are
executed after the occurrence of an exception.
Workaround: Software exception handlers that rely on the LER MSR value should read the LER MSR
before executing VERW/VERR/LSL/LAR instructions.
Status: For the steppings affected, see the Summary Tables of Changes.
AH5. DR3 Address Match on MOVD/MOVQ/MOVNTQ Memory Store
Instruction May Incorrectly Increment Performance Monitoring Count
for Saturating SIMD Instructions Retired (Event CFH)
Problem: Performance monitoring for Event CFH normally increments on saturating SIMD
instruction retired. Regardless of DR7 programming, if the linear address of a retiring
memory store MOVD/MOVQ/MOVNTQ instruction executed matches the address in
DR3, the CFH counter may be incorrectly incremented.
Implication: The value observed for performance monitoring count for saturating SIMD instructions
retired may be too high. The size of the error is dependent on the number of
occurrences of the conditions described above, while the counter is active.
None Identified.
Status: For the steppings affected, see the Summary Tables of Changes.
AH6. SYSRET May Incorrectly Clear RF (Resume Flag) in the RFLAGS
Register
Problem: In normal operation, SYSRET will restore the value of RFLAGS from R11 (the value
previously saved upon execution of the SYSCALL instruction). Due to this erratum, the
RFLAGS.RF bit will be unconditionally cleared after execution of the SYSRET
instruction.
Implication: The SYSRET instruction can not be used if the RF flag needs to be set after returning
from a system call. Intel has not observed this erratum with any commercially
available software.
Workaround: Use the IRET instruction to return from a system call, if RF flag has to be set after the
return.
Status: For the steppings affected, see the Summary Tables of Changes