linux-kernel - [PATCH] perf/x86/lbr: Reset LBR

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Date:   Fri,  5 Nov 2021 00:20:51 -0700
From:   Wanpeng Li <kernellwp@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...hat.com>, Like Xu <likexu@...cent.com>
Subject: [PATCH] perf/x86/lbr: Reset LBR_SELECT during vlbr reset

From: Wanpeng Li <wanpengli@...cent.com>

lbr_select in kvm guest has residual data even if kvm guest is poweroff.
We can get residual data in the next boot. Because lbr_select is not
reset during kvm vlbr release. Let's reset LBR_SELECT during vlbr reset.

Cc: Like Xu <likexu@...cent.com>
Signed-off-by: Wanpeng Li <wanpengli@...cent.com>
---
 arch/x86/events/intel/lbr.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/events/intel/lbr.c b/arch/x86/events/intel/lbr.c
index 9e6d6eaeb4cb..1076de93a2f5 100644
--- a/arch/x86/events/intel/lbr.c
+++ b/arch/x86/events/intel/lbr.c
@@ -279,6 +279,8 @@ void intel_pmu_lbr_reset(void)
 
 	cpuc->last_task_ctx = NULL;
 	cpuc->last_log_id = 0;
+	if (!static_cpu_has(X86_FEATURE_ARCH_LBR) && cpuc->lbr_select)
+		wrmsrl(MSR_LBR_SELECT, 0);
 }
 
 /*
-- 
2.25.1