Specification Update

Errata
Specification Update 37
W10. Inconsistent Reporting of Data Breakpoints on FP (MMX
Technology) Loads
Problem: The reporting of data breakpoints on either FP or MMX technology loads
is dependent upon the code faulting behavior prior to the execution of
the load. If there is a fault pending prior to the execution of the load
and FP exceptions are enabled there is a chance that data breakpoint
on successive FP/MMX technology Loads may be reported twice.
Implication: Software debuggers should be aware of this possibility. There should be
no implications to software operated outside of a debug environment.
Workaround: None identified.
Status: For the steppings affected, see the Summary Tables of Changes.
W11. An Enabled Debug Breakpoint or Single Step Trap May Be Taken after
MOV SS/POP SS Instruction if it is Followed by an Instruction That
Signals a Floating Point Exception
Problem: A MOV SS/POP SS instruction should inhibit all interrupts including
debug breakpoints until after execution of the following instruction. This
is intended to allow the sequential execution of MOV SS/POP SS and
MOV [r/e]SP, [r/e]BP instructions without having an invalid stack
during interrupt handling. However, an enabled debug breakpoint or
single step trap may be taken after MOV SS/POP SS if this instruction is
followed by an instruction that signals a floating point exception rather
than a MOV [r/e]SP, [r/e]BP instruction. This results in a debug
exception being signaled on an unexpected instruction boundary since
the MOV SS/POP SS and the following instruction should be executed
atomically.
Implication: This can result in incorrect signaling of a debug exception and possibly
a mismatched Stack Segment and Stack Pointer. If MOV SS/POP SS is
not followed by a MOV [r/e]SP, [r/e]BP, there may be a mismatched
Stack Segment and Stack Pointer on any exception. Intel has not
observed this erratum with any commercially available software, or
system.
Workaround: As recommended in the IA32 Intel® Architecture Software Developer’s Manual, the
use of MOV SS/POP SS in conjunction with MOV [r/e]SP, [r/e]BP will avoid the failure
since the MOV [r/e]SP, [r/e]BP will not generate a floating point exception. Developers
of debug tools should be aware of the potential incorrect debug event signaling
created by this erratum.
Status: For the steppings affected, see the Summary Tables of Changes.
W12. SysEnter and SysExit Instructions May Write Incorrect
Requestor Privilege Level (RPL) in the FP Code Segment
Selector (FCS)