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

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Date:   Thu, 11 Nov 2021 12:22:14 -0000
From:   "tip-bot2 for Wanpeng Li" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Wanpeng Li <wanpengli@...cent.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: perf/urgent] perf/x86/lbr: Reset LBR_SELECT during vlbr reset

The following commit has been merged into the perf/urgent branch of tip:

Commit-ID:     0fe39a3929ac7af980347814d552a734b51adacf
Gitweb:        https://git.kernel.org/tip/0fe39a3929ac7af980347814d552a734b51adacf
Author:        Wanpeng Li <wanpengli@...cent.com>
AuthorDate:    Fri, 05 Nov 2021 00:20:51 -07:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Thu, 11 Nov 2021 13:09:34 +01:00

perf/x86/lbr: Reset LBR_SELECT during vlbr reset

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.

Signed-off-by: Wanpeng Li <wanpengli@...cent.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Link: https://lkml.kernel.org/r/1636096851-36623-1-git-send-email-wanpengli@tencent.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 6b72e9b..8043213 100644
--- a/arch/x86/events/intel/lbr.c
+++ b/arch/x86/events/intel/lbr.c
@@ -265,6 +265,8 @@ 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);
 }
 
 /*