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From: Jiri Olsa <jolsa@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>, Kan Liang <kan.liang@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>,
	David Carrillo-Cisneros <davidcc@google.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	lkml <linux-kernel@vger.kernel.org>,
	Ingo Molnar <mingo@kernel.org>,
	Namhyung Kim <namhyung@kernel.org>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Andi Kleen <ak@linux.intel.com>, Tom Vaden <tom.vaden@hpe.com>
Subject: [RFC] perf/x86/intel: Disable check_msr for real hw
Date: Fri, 14 Jun 2019 13:28:53 +0200	[thread overview]
Message-ID: <20190614112853.GC4325@krava> (raw)

hi,
the HPE server can do POST tracing and have enabled LBR
tracing during the boot, which makes check_msr fail falsly.

It looks like check_msr code was added only to check on guests
MSR access, would it be then ok to disable check_msr for real
hardware? (as in patch below)

We could also check if LBR tracing is enabled and make
appropriate checks, but this change is simpler ;-)

ideas? thanks,
jirka


---
 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 71001f005bfe..1194ae7e1992 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 up with potentionaly enabled regs.
+	 */
+	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
-- 
2.21.0


             reply	other threads:[~2019-06-14 11:28 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-14 11:28 Jiri Olsa [this message]
2019-06-14 13:33 ` Peter Zijlstra
2019-06-14 13:45 ` Liang, Kan
2019-06-16 14:13   ` [PATCH] " Jiri Olsa
2019-06-16 20:56     ` Vaden, Tom (HPE Server OS Architecture)
2019-06-17 14:41     ` [tip:perf/core] perf/x86/intel: Disable check_msr for real HW tip-bot for Jiri Olsa
2019-06-21 17:48 ` [RFC] perf/x86/intel: Disable check_msr for real hw Andi Kleen
2019-06-23 22:40   ` Jiri Olsa
2019-06-23 23:44     ` Vaden, Tom (HPE Server OS Architecture)
2019-06-24  8:06     ` Paolo Bonzini
2019-06-24 16:46     ` Andi Kleen
2019-06-24 18:06       ` Jiri Olsa
2019-06-24 18:38         ` Andi Kleen
2019-06-24 18:49           ` Jiri Olsa

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