From: Kan Liang <kan.li...@intel.com>
This patch fixes an issue which introduced by commit
1a78d93750bb5f61abdc59a91fc3bd06a214542a ("perf/x86/intel: Streamline
LBR MSR handling in PMI").
The old patch not only avoids writing LBR_SELECT MSR in PMI, but also
avoids updating lbr_select variable. So in PMI, FREEZE_LBRS_ON_PMI bit
is always mistakenly set for IA32_DEBUGCTLMSR MSR, which causes
superfluous increase/decrease of LBR_TOS when collecting LBR callstack.
Reported-by: Milian Wolff <m...@milianw.de>
Signed-off-by: Kan Liang <kan.li...@intel.com>
---
arch/x86/kernel/cpu/perf_event_intel_lbr.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kernel/cpu/perf_event_intel_lbr.c
b/arch/x86/kernel/cpu/perf_event_intel_lbr.c
index b2c9475..a1d07c7 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_lbr.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_lbr.c
@@ -151,10 +151,9 @@ static void __intel_pmu_lbr_enable(bool pmi)
* No need to reprogram LBR_SELECT in a PMI, as it
* did not change.
*/
- if (cpuc->lbr_sel && !pmi) {
- lbr_select = cpuc->lbr_sel->config;
+ lbr_select = cpuc->lbr_sel->config;
+ if (cpuc->lbr_sel && !pmi)
wrmsrl(MSR_LBR_SELECT, lbr_select);
- }
rdmsrl(MSR_IA32_DEBUGCTLMSR, debugctl);
orig_debugctl = debugctl;
--
1.8.3.1
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