Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932066AbaKEDKs (ORCPT ); Tue, 4 Nov 2014 22:10:48 -0500 Received: from mga01.intel.com ([192.55.52.88]:23408 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753352AbaKEDKr (ORCPT ); Tue, 4 Nov 2014 22:10:47 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.07,317,1413270000"; d="scan'208";a="617287018" From: Kan Liang To: a.p.zijlstra@chello.nl, eranian@google.com Cc: linux-kernel@vger.kernel.org, mingo@redhat.com, paulus@samba.org, acme@kernel.org, jolsa@redhat.com, ak@linux.intel.com, Kan Liang Subject: [PATCH V7 14/17] perf, x86: disable FREEZE_LBRS_ON_PMI when LBR operates in callstack mode Date: Tue, 4 Nov 2014 21:56:10 -0500 Message-Id: <1415156173-10035-15-git-send-email-kan.liang@intel.com> X-Mailer: git-send-email 1.8.3.2 In-Reply-To: <1415156173-10035-1-git-send-email-kan.liang@intel.com> References: <1415156173-10035-1-git-send-email-kan.liang@intel.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Yan, Zheng 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 Signed-off-by: Kan Liang --- arch/x86/kernel/cpu/perf_event_intel_lbr.c | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-) diff --git a/arch/x86/kernel/cpu/perf_event_intel_lbr.c b/arch/x86/kernel/cpu/perf_event_intel_lbr.c index a9e3a0d..12a87b0 100644 --- a/arch/x86/kernel/cpu/perf_event_intel_lbr.c +++ b/arch/x86/kernel/cpu/perf_event_intel_lbr.c @@ -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); } -- 1.8.3.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/