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

tip-bot for Andy Lutomirski
2015-07-06T15:42:37Z

Commit-ID: 9cfa1a0279e22063a727fd204a75cf3672860d83
Gitweb: http://git.kernel.org/tip/9cfa1a0279e22063a727fd204a75cf3672860d83
Author: Andy Lutomirski <luto@kernel.org>
AuthorDate: Thu, 25 Jun 2015 18:44:00 +0200
Committer: Ingo Molnar <mingo@kernel.org>
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@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Huang Rui <ray.huang@amd.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kvm ML <kvm@vger.kernel.org>
Link: http://lkml.kernel.org/r/bd1a277c71321b67c4794970cb5ace05efe21ab6.1434501121.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
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();