[tip:x86/asm] x86/asm/tsc: Use the full 64-bit TSC in delay_tsc()

[tip-bot for Andy Lutomirski]

Commit-ID:  9cfa1a0279e22063a727fd204a75cf3672860d83
Gitweb:     http://git.kernel.org/tip/9cfa1a0279e22063a727fd204a75cf3672860d83
Author:     Andy Lutomirski <luto@xxxxxxxxxx>
AuthorDate: Thu, 25 Jun 2015 18:44:00 +0200
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Mon, 6 Jul 2015 15:23:27 +0200

x86/asm/tsc: Use the full 64-bit TSC in delay_tsc()

As a very minor optimization, delay_tsc() was only using the low
32 bits of the TSC. It's a delay function, so just use the whole
thing.

Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Brian Gerst <brgerst@xxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Huang Rui <ray.huang@xxxxxxx>
Cc: John Stultz <john.stultz@xxxxxxxxxx>
Cc: Len Brown <lenb@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: kvm ML <kvm@xxxxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/bd1a277c71321b67c4794970cb5ace05efe21ab6.1434501121.git.luto@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 arch/x86/lib/delay.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/lib/delay.c b/arch/x86/lib/delay.c
index 9a52ad0..35115f3 100644
--- a/arch/x86/lib/delay.c
+++ b/arch/x86/lib/delay.c
@@ -49,16 +49,16 @@ static void delay_loop(unsigned long loops)
 /* TSC based delay: */
 static void delay_tsc(unsigned long __loops)
 {
-	u32 bclock, now, loops = __loops;
+	u64 bclock, now, loops = __loops;
 	int cpu;
 
 	preempt_disable();
 	cpu = smp_processor_id();
 	rdtsc_barrier();
-	rdtscl(bclock);
+	bclock = native_read_tsc();
 	for (;;) {
 		rdtsc_barrier();
-		rdtscl(now);
+		now = native_read_tsc();
 		if ((now - bclock) >= loops)
 			break;
 
@@ -80,7 +80,7 @@ static void delay_tsc(unsigned long __loops)
 			loops -= (now - bclock);
 			cpu = smp_processor_id();
 			rdtsc_barrier();
-			rdtscl(bclock);
+			bclock = native_read_tsc();
 		}
 	}
 	preempt_enable();
--
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