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perf/x86/intel: Disable FREEZE_LBRS_ON_PMI when LBR operates in callstack mode

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LBR callstack is designed for PEBS, It does not work well with
FREEZE_LBRS_ON_PMI for non PEBS event. If FREEZE_LBRS_ON_PMI is set for
non PEBS event, PMIs near call/return instructions may cause superfluous
increase/decrease of LBR_TOS.

This patch modifies __intel_pmu_lbr_enable() to not enable
FREEZE_LBRS_ON_PMI when LBR operates in callstack mode. We currently
don't use LBR callstack to capture kernel space callchain, so disabling
FREEZE_LBRS_ON_PMI should not be a problem.

Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com>
Signed-off-by: Kan Liang <kan.liang@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: eranian@google.com
Cc: jolsa@redhat.com
Link: http://lkml.kernel.org/r/1415156173-10035-15-git-send-email-kan.liang@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Yan, Zheng 2014-11-04 21:56:10 -05:00 committed by Ingo Molnar
parent 4b85490099
commit 2c70d0086e
1 changed files with 13 additions and 4 deletions
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17
arch/x86/kernel/cpu/perf_event_intel_lbr.c
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@ -131,14 +131,23 @@ static void intel_pmu_lbr_filter(struct cpu_hw_events *cpuc);
static void __intel_pmu_lbr_enable(void)
{
u64 debugctl;
struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
u64 debugctl, lbr_select = 0;
if (cpuc->lbr_sel)
wrmsrl(MSR_LBR_SELECT, cpuc->lbr_sel->config);
if (cpuc->lbr_sel) {
lbr_select = cpuc->lbr_sel->config;
wrmsrl(MSR_LBR_SELECT, lbr_select);
}
rdmsrl(MSR_IA32_DEBUGCTLMSR, debugctl);
debugctl |= (DEBUGCTLMSR_LBR | DEBUGCTLMSR_FREEZE_LBRS_ON_PMI);
debugctl |= DEBUGCTLMSR_LBR;
/*
* LBR callstack does not work well with FREEZE_LBRS_ON_PMI.
* If FREEZE_LBRS_ON_PMI is set, PMI near call/return instructions
* may cause superfluous increase/decrease of LBR_TOS.
*/
if (!(lbr_select & LBR_CALL_STACK))
debugctl |= DEBUGCTLMSR_FREEZE_LBRS_ON_PMI;
wrmsrl(MSR_IA32_DEBUGCTLMSR, debugctl);
}