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>

diff --git a/arch/i386/kernel/cpu/perfctr-watchdog.c b/arch/i386/kernel/cpu/perfctr-watchdog.c
index 30b5e48aa76b84375fc408ce866305980d2eda22..572900398def0a7bcda281aa572ebe2cb6f05cc2 100644 (file)
--- 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