Errata
Specification Update
45
AN87.
Code Segment Limit/Canonical Faults on RSM May Be Serviced before
Higher Priority Interrupts/Exceptions
Problem:
Normally, when the processor encounters a Segment Limit or Canonical Fault due to
code execution, a #GP (General Protection Exception) fault is generated after all
higher priority Interrupts and exceptions are serviced. Due to this erratum, if RSM
(Resume from System Management Mode) returns to execution flow that results in a
Code Segment Limit or Canonical Fault, the #GP fault may be serviced before a higher
priority Interrupt or Exception (for example 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. Intel has not observed this erratum on any commercially
available software.
Workaround:
None Identified.
Status:
For the steppings affected, see the
AN88.
LBR, BTS, BTM May Report a Wrong Address When an
Exception/Interrupt Occurs in 64-bit Mode
Problem:
An exception/interrupt event should be transparent to the LBR (Last Branch Record),
BTS (Branch Trace Store) and BTM (Branch Trace Message) mechanisms. However,
during a specific boundary condition where the exception/interrupt occurs right after
the execution of an instruction at the lower canonical boundary (0x00007FFFFFFFFFFF)
in 64-bit mode, the LBR return registers will save a wrong return address with bits 63
to 48 incorrectly sign extended to all 1’s. Subsequent BTS and BTM operations which
report the LBR will also be incorrect.
Implication:
LBR, BTS and BTM may report incorrect information in the event of an
exception/interrupt.
Workaround:
None identified.
Status:
For the steppings affected, see the
AN89.
CMPSB, LODSB, or SCASB in 64-bit Mode with Count Greater or Equal
to 2
48
May Terminate Early
Problem:
In 64-bit Mode CMPSB, LODSB, or SCASB executed with a repeat prefix and count
greater than or equal to 2
48
may terminate early. Early termination may result in one
of the following.
•
The last iteration not being executed
•
Signaling of a canonical limit fault (#GP) on the last iteration
Implication:
While in 64-bit mode, with count greater or equal to 2
48
, repeat string operations
CMPSB, LODSB or SCASB may terminate without completing the last iteration. Intel
has not observed this erratum with any commercially available software.
Workaround:
Do not use repeated string operations with RCX greater than or equal to 2
48
.
Status:
