arch/x86/kernel/cpu/perf_event_msr.c: use sign_extend64() for sign extension

Signed-off-by: NMartin Kepplinger <martin.kepplinger@theobroma-systems.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: George Spelvin <linux@horizon.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Maxime Coquelin <maxime.coquelin@st.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Yury Norov <yury.norov@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

arch/x86/kernel/cpu/perf_event_msr.c

@@ -163,10 +163,9 @@ static void msr_event_update(struct perf_event *event)
 		goto again;
 
 	delta = now - prev;
-	if (unlikely(event->hw.event_base == MSR_SMI_COUNT)) {
-		delta <<= 32;
-		delta >>= 32; /* sign extend */
-	}
+	if (unlikely(event->hw.event_base == MSR_SMI_COUNT))
+		delta = sign_extend64(delta, 31);
+
 	local64_add(now - prev, &event->count);
 }