Commit 9cfa1a02 authored Jun 25, 2015 by Andy Lutomirski Committed by Ingo Molnar Jul 06, 2015

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>

parent ec69de52

arch/x86/lib/delay.c

+4 −4

Original line number	Diff line number	Diff line
		@@ -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();