User Guide

Errata
38 Specification Update
KBL056 CTR_FRZ May Not Freeze Some Counters
Problem
IA32_PERF_GLOBAL_STATUS.CTR_FRZ (MSR 38EH, bit 59) is set when either (1)
IA32_DEBUGCTL.FREEZE_PERFMON_ON_PMI (MSR 1D9H, bit 12) is set and a PMI is
triggered, or (2) software sets bit 59 of IA32_PERF_GLOBAL_STATUS_SET (MSR
391H). When set, CTR_FRZ should stop all core performance monitoring counters
from counting. However, due to this erratum, IA32_PMC4-7 (MSR C5-C8H) may not
stop counting. IA32_PMC4-7 are only available when a processor core is not shared
by two logical processors.
Implication
General performance monitoring counters 4-7 may not freeze when
IA32_PERF_GLOBAL_STATUS.CTR_FRZ is set.
Workaround None identified.
Status For the steppings affected, see the Summary Table of Changes.
KBL057
Instructions And Branches Retired Performance Monitoring Events May
Overcount
Problem
The performance monitoring events INST_RETIRED (Event C0H; any Umask value)
and BR_INST_RETIRED (Event C4H; any Umask value) count instructions retired and
branches retired, respectively. However, due to this erratum, these events may
overcount in certain conditions when:
- Executing VMASKMOV* instructions with at least one masked vector element
- Executing REP MOVS or REP STOS with Fast Strings enabled (IA32_MISC_ENABLES
MSR (1A0H), bit 0 set)
- An MPX #BR exception occurred on BNDLDX/BNDSTX instructions and the
BR_INST_RETIRED (Event C4H; Umask is 00H or 04H) is used.
Implication
INST_RETIRED and BR_INST_RETIRED performance monitoring events may
overcount.
Workaround None identified.
Status For the steppings affected, see the Summary Table of Changes.
KBL058 Some OFFCORE_RESPONSE Performance Monitoring Events May Overcount
Problem
The performance monitoring events OFFCORE_RESPONSE (Events B7H and BBH)
should count off-core responses matching the request-response configuration
specified in MSR_OFFCORE_RSP_0 and MSR_OFFCORE_RSP_1 (1A6H and 1A7H,
respectively) for core-originated requests. However, due to this erratum, DMND_RFO
(bit 1), DMND_IFETCH (bit 2) and OTHER (bit 15) request types may overcount.
Implication Some OFFCORE_RESPONSE events may overcount.
Workaround
None identified. Software may use the following model-specific events that provide
related performance monitoring data: OFFCORE_REQUESTS (all sub-events),
L2_TRANS.L2_WB and L2_RQSTS.PF_MISS.
Status For the steppings affected, see the Summary Table of Changes.