[patch 18/20] i386: Handle P6s without performance counters in nmiwatchdog

[Greg KH]

-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Andi Kleen <ak@xxxxxxx>

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@xxxxxxxxxxxx>
Signed-off-by: Andi Kleen <ak@xxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 arch/i386/kernel/cpu/perfctr-watchdog.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- 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 nm
 	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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