linux-kernel - [tip:perf/core] perf/x86/intel: Disable check

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Date:   Mon, 17 Jun 2019 07:41:12 -0700
From:   tip-bot for Jiri Olsa <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
        mingo@...nel.org, kan.liang@...ux.intel.com, peterz@...radead.org,
        acme@...nel.org, alexander.shishkin@...ux.intel.com,
        jolsa@...hat.com, jolsa@...nel.org, tom.vaden@....com,
        hpa@...or.com, namhyung@...nel.org, tglx@...utronix.de
Subject: [tip:perf/core] perf/x86/intel: Disable check_msr for real HW

Commit-ID:  d0e1a507bdc761a14906f03399d933ea639a1756
Gitweb:     https://git.kernel.org/tip/d0e1a507bdc761a14906f03399d933ea639a1756
Author:     Jiri Olsa <jolsa@...hat.com>
AuthorDate: Sun, 16 Jun 2019 16:13:13 +0200
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Mon, 17 Jun 2019 12:36:24 +0200

perf/x86/intel: Disable check_msr for real HW

Tom Vaden reported false failure of the check_msr() function, because
some servers can do POST tracing and enable LBR tracing during
bootup.

Kan confirmed that check_msr patch was to fix a bug report in
guest, so it's ok to disable it for real HW.

Reported-by: Tom Vaden <tom.vaden@....com>
Signed-off-by: Jiri Olsa <jolsa@...nel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Acked-by: Tom Vaden <tom.vaden@....com>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Liang Kan <kan.liang@...ux.intel.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: https://lkml.kernel.org/r/20190616141313.GD2500@krava
[ Readability edits. ]
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 arch/x86/events/intel/core.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index 5e6ae481dee7..bda450ff51ee 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -20,6 +20,7 @@
 #include <asm/intel-family.h>
 #include <asm/apic.h>
 #include <asm/cpu_device_id.h>
+#include <asm/hypervisor.h>
 
 #include "../perf_event.h"
 
@@ -4050,6 +4051,13 @@ static bool check_msr(unsigned long msr, u64 mask)
 {
 	u64 val_old, val_new, val_tmp;
 
+	/*
+	 * Disable the check for real HW, so we don't
+	 * mess with potentionaly enabled registers:
+	 */
+	if (hypervisor_is_type(X86_HYPER_NATIVE))
+		return true;
+
 	/*
 	 * Read the current value, change it and read it back to see if it
 	 * matches, this is needed to detect certain hardware emulators