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authorKan Liang <kan.liang@intel.com>2015-08-17 08:37:31 -0400
committerIngo Molnar <mingo@kernel.org>2015-09-13 11:27:22 +0200
commitdeb27519bf1f4b21a761c0675dbdf1196df7d72a (patch)
tree3c7f88c756c4316b8e10265147b9c84795124797 /arch
parentd2878d642a4edd1d57c691dc3e4d7847cbf9d442 (diff)
downloadlinux-deb27519bf1f4b21a761c0675dbdf1196df7d72a.tar.bz2
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@milianw.de> Signed-off-by: Kan Liang <kan.liang@intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vincent.weaver@maine.edu> Link: http://lkml.kernel.org/r/1439815051-8616-1-git-send-email-kan.liang@intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kernel/cpu/perf_event_intel_lbr.c5
1 files 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 b2c9475b7ff2..a1d07c71d3b6 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;