Commit-ID: deb27519bf1f4b21a761c0675dbdf1196df7d72a
Gitweb: http://git.kernel.org/tip/deb27519bf1f4b21a761c0675dbdf1196df7d72a
Author: Kan Liang <kan.liang@xxxxxxxxx>
AuthorDate: Mon, 17 Aug 2015 08:37:31 -0400
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Sun, 13 Sep 2015 11:27:22 +0200
perf/x86/intel: Fix LBR callstack issue caused by FREEZE_LBRS_ON_PMI
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 <mail@xxxxxxxxxx>
Signed-off-by: Kan Liang <kan.liang@xxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Stephane Eranian <eranian@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Vince Weaver <vincent.weaver@xxxxxxxxx>
Link: http://lkml.kernel.org/r/1439815051-8616-1-git-send-email-kan.liang@xxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
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;
--
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