perf/x86/msr: Fix SMI overflow

We compute 'delta' and properly sign extend it and then ignore it and recompute the raw value, loosing the sign extention. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Jiri Olsa <jolsa@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Stephane Eranian <eranian@google.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Vince Weaver <vincent.weaver@maine.edu> Cc: kan.liang@intel.com Cc: linux-kernel@vger.kernel.org Cc: luto@kernel.org Cc: ray.huang@amd.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
torvalds · May 12, 2016 · 3c3116b · 3c3116b
1 parent ec336c8
commit 3c3116b
Showing 1 changed file with 1 addition and 1 deletion.
diff --git a/arch/x86/events/msr.c b/arch/x86/events/msr.c
@@ -166,7 +166,7 @@ static void msr_event_update(struct perf_event *event)
 	if (unlikely(event->hw.event_base == MSR_SMI_COUNT))
 		delta = sign_extend64(delta, 31);
 
-	local64_add(now - prev, &event->count);
+	local64_add(delta, &event->count);
 }
 
 static void msr_event_start(struct perf_event *event, int flags)