[PATCH AUTOSEL 5.1 100/219] perf/x86/intel: Disable check_msr for real HW

Sasha Levin
2019-07-15T14:09:32Z

From: Jiri Olsa <jolsa@redhat.com>

[ Upstream commit d0e1a507bdc761a14906f03399d933ea639a1756 ]

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@hpe.com>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Tom Vaden <tom.vaden@hpe.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Liang Kan <kan.liang@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20190616141313.GD2500@krava
[ Readability edits. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.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 82dad001d1ea..a50e182c38b6 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -19,6 +19,7 @@
#include <asm/intel-family.h>
#include <asm/apic.h>
#include <asm/cpu_device_id.h>
+#include <asm/hypervisor.h>

#include "../perf_event.h"

@@ -3927,6 +3928,13 @@ 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
--
2.20.1