Specification Update

Errata
20 Specification Update
AM13 LER MSRs May be Incorrectly Updated
Problem: The LER (Last Exception Record) MSRs, MSR_LER_FROM_LIP
(1DDH) and MSR_LER_TO_LIP (1DEH) may contain incorrect values after any of the
following:
• Either STPCLK#, NMI (NonMaskable Interrupt) or external interrupts
• CMP or TEST instructions with an uncacheable memory operand followed by a
conditional jump
• STI/POP SS/MOV SS instructions followed by CMP or TEST instructions
and then by a conditional jump
Implication: When the conditions for this erratum occur, the value of the LER MSRs may be
incorrectly updated.
Workaround: None identified.
Status: For the steppings affected, see the Summary Tables of Changes.
AM14 Performance Monitoring Events for Retired Instructions (C0H) May Not be
Accurate
Problem: The INST_RETIRED performance monitor may miscount retired instructions as follows:
• Repeat string and repeat I/O operations are not counted when a hardware
interrupt is received during or after the last iteration of the repeat flow.
• VMLAUNCH and VMRESUME instructions are not counted.
• HLT and MWAIT instructions are not counted.
The following instructions, if executed during HLT or MWAIT events, are also not
counted:
• RSM from a C-state SMI during an MWAIT instruction.
• RSM from an SMI during a HLT instruction.
Implication: There may be a smaller than expected value in the INST_RETIRED performance
monitoring counter. The extent to which this value is smaller than expected is
determined by the frequency of the above cases.
Workaround: None Identified.
Status: For the steppings affected, see the Summary Tables of Changes.