Messages in this thread Patch in this message | | | Date | Sun, 13 Sep 2015 04:09:09 -0700 | From | tip-bot for Kan Liang <> | Subject | [tip:perf/core] perf/x86/intel: Fix LBR callstack issue caused by FREEZE_LBRS_ON_PMI |
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Commit-ID: deb27519bf1f4b21a761c0675dbdf1196df7d72a Gitweb: http://git.kernel.org/tip/deb27519bf1f4b21a761c0675dbdf1196df7d72a Author: Kan Liang <kan.liang@intel.com> AuthorDate: Mon, 17 Aug 2015 08:37:31 -0400 Committer: Ingo Molnar <mingo@kernel.org> 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@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> --- 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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