From 57c22f49e4c7d27a03e109a317c30b12f1bae0b2 Mon Sep 17 00:00:00 2001
From: Andi Kleen <ak@suse.de>
Date: Sun, 22 Jul 2007 11:12:39 +0200
Subject: [PATCH] i386: Handle P6s without performance counters in nmi watchdog

I got an oops while booting a 32bit kernel on KVM because it doesn't
implement performance counters used by the NMI watchdog. Handle this
case.

Cc: Avi Kivity <avi@qumranet.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 arch/i386/kernel/cpu/perfctr-watchdog.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/i386/kernel/cpu/perfctr-watchdog.c b/arch/i386/kernel/cpu/perfctr-watchdog.c
index 30b5e48aa76b..572900398def 100644
--- a/arch/i386/kernel/cpu/perfctr-watchdog.c
+++ b/arch/i386/kernel/cpu/perfctr-watchdog.c
@@ -346,7 +346,9 @@ static int setup_p6_watchdog(unsigned nmi_hz)
 	perfctr_msr = MSR_P6_PERFCTR0;
 	evntsel_msr = MSR_P6_EVNTSEL0;
 
-	wrmsrl(perfctr_msr, 0UL);
+	/* KVM doesn't implement this MSR */
+	if (wrmsr_safe(perfctr_msr, 0, 0) < 0)
+		return 0;
 
 	evntsel = P6_EVNTSEL_INT
 		| P6_EVNTSEL_OS
-- 
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