linux-kernel - Re: [PATCH v6 bpf-next 1/3] perf: enable branch record for software events

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Message-ID: <YTtjeyfJXXiDielu@hirez.programming.kicks-ass.net>
Date:   Fri, 10 Sep 2021 15:54:03 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Song Liu <songliubraving@...com>
Cc:     bpf@...r.kernel.org, linux-kernel@...r.kernel.org, acme@...nel.org,
        mingo@...hat.com, kjain@...ux.ibm.com, kernel-team@...com,
        John Fastabend <john.fastabend@...il.com>,
        Andrii Nakryiko <andrii@...nel.org>
Subject: Re: [PATCH v6 bpf-next 1/3] perf: enable branch record for software
 events

On Fri, Sep 10, 2021 at 12:40:51PM +0200, Peter Zijlstra wrote:

> The below seems to cure that.

Seems I lost a hunk, fold below.

diff --git a/arch/x86/events/intel/lbr.c b/arch/x86/events/intel/lbr.c
index 9e6d6eaeb4cb..6b72e9b55c69 100644
--- a/arch/x86/events/intel/lbr.c
+++ b/arch/x86/events/intel/lbr.c
@@ -228,20 +228,6 @@ static void __intel_pmu_lbr_enable(bool pmi)
 		wrmsrl(MSR_ARCH_LBR_CTL, lbr_select | ARCH_LBR_CTL_LBREN);
 }
 
-static void __intel_pmu_lbr_disable(void)
-{
-	u64 debugctl;
-
-	if (static_cpu_has(X86_FEATURE_ARCH_LBR)) {
-		wrmsrl(MSR_ARCH_LBR_CTL, 0);
-		return;
-	}
-
-	rdmsrl(MSR_IA32_DEBUGCTLMSR, debugctl);
-	debugctl &= ~(DEBUGCTLMSR_LBR | DEBUGCTLMSR_FREEZE_LBRS_ON_PMI);
-	wrmsrl(MSR_IA32_DEBUGCTLMSR, debugctl);
-}
-
 void intel_pmu_lbr_reset_32(void)
 {
 	int i;
@@ -779,8 +765,12 @@ void intel_pmu_lbr_disable_all(void)
 {
 	struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
 
-	if (cpuc->lbr_users && !vlbr_exclude_host())
+	if (cpuc->lbr_users && !vlbr_exclude_host()) {
+		if (static_cpu_has(X86_FEATURE_ARCH_LBR))
+			return __intel_pmu_arch_lbr_disable();
+
 		__intel_pmu_lbr_disable();
+	}
 }
 
 void intel_pmu_lbr_read_32(struct cpu_hw_events *cpuc)