Specification Update

Errata
60 Specification Update
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.
W65. Performance Monitoring Events for Retired Floating Point
Operations (C1h) May Not Be Accurate
Problem: Performance monitoring events that count retired floating point
operations may be too high.
Implication: The Performance Monitoring Event may have an inaccurate count.
Workaround: None identified.
Status: For the steppings affected, see the Summary Tables of Changes.
W66. Global Pages in the Data Translation Look-Aside Buffer
(DTLB) May Not Be Flushed by RSM instruction before
Restoring the Architectural State from SMRAM
Problem: The Resume from System Management Mode (RSM) instruction does
not flush global pages from the Data Translation Look-Aside Buffer
(DTLB) prior to reloading the saved architectural state.
Implication: If SMM turns on paging with global paging enabled and then maps any
of linear addresses of SMRAM using global pages, RSM load may load
data from the wrong location.
Workaround: Do not use global pages in system management mode.
Status: For the steppings affected, see the Summary Tables of Changes.
W67. Data Breakpoint/Single Step on MOV SS/POP SS May Be
Lost after Entry into SMM
Problem: Data Breakpoint/Single Step exceptions are normally blocked for one
instruction following MOV SS/POP SS instructions. Immediately after
executing these instructions, if the processor enters SMM (System
Management Mode), upon RSM (resume from SMM) operation, normal
processing of Data Breakpoint/Single Step exceptions is restored.
Because of this erratum, Data Breakpoints/Single step exceptions on MOVSS/POPSS
instructions may be lost under one of the following conditions.
1. Following SMM entry and after RSM, the next instruction to be executed is HLT or
MWAIT
2. SMM entry after executing MOV SS/POP SS is the result of executing an I/O
instruction that triggers a synchronous SMI (System Management Interrupt)
Implication: Data Breakpoints/Single step operation on MOV SS/POP SS instructions
may be unreliable in the presence of SMIs.
Workaround: None Identified.