Intel Xeon Processor LV and ULV Specification Update

Errata
Specification Update 27
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 may load data from the wrong location.
Workaround: Workaround: Do not use global pages in System Management Mode.
Status: For the steppings affected, see the Summary Tables of Changes.
AF30. Data Breakpoint/Single Step on MOV SS/POP SS May Be Lost after
Entry into SMM
Problem: 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.
Status: For the steppings affected, see the Summary Tables of Changes.
AF31. CS Limit Violation on RSM May Be Serviced before Higher Priority
Interrupts/Exceptions
Problem: When the processor encounters a CS (Code Segment) limit violation, a #GP (General
Protection Exception) fault is generated after all higher priority Interrupts and
exceptions are serviced. Because of this erratum, if RSM (Resume from System
Management Mode) returns to execution flow where a CS limit violation occurs, the
#GP fault may be serviced before a higher priority Interrupt or Exception (e.g. NMI
(Non-Maskable Interrupt), Debug break(#DB), Machine Check (#MC), etc).
Implication: Operating systems may observe a #GP fault being serviced before higher priority
interrupts and Exceptions.
Workaround: None identified.
Status: For the steppings affected, see the Summary Tables of Changes.