Commit 881d7bf8 authored Jun 25, 2015 by Andy Lutomirski Committed by Ingo Molnar Jul 06, 2015

x86/asm/tsc, kvm: Remove vget_cycles()



The only caller was KVM's read_tsc(). The only difference
between vget_cycles() and native_read_tsc() was that
vget_cycles() returned zero instead of crashing on TSC-less
systems. KVM already checks vclock_mode() before calling that
function, so the extra check is unnecessary. Also, KVM
(host-side) requires the TSC to exist.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
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/20615df14ae2eb713ea7a5f5123c1dc4c7ca993d.1434501121.git.luto@kernel.org


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent c6e5ca35

arch/x86/include/asm/tsc.h

+0 −13

Original line number	Diff line number	Diff line
		@@ -32,19 +32,6 @@ static inline cycles_t get_cycles(void)
		return ret;
		}

		static __always_inline cycles_t vget_cycles(void)
		{
		/*
		* We only do VDSOs on TSC capable CPUs, so this shouldn't
		* access boot_cpu_data (which is not VDSO-safe):
		*/
		#ifndef CONFIG_X86_TSC
		if (!cpu_has_tsc)
		return 0;
		#endif
		return (cycles_t)native_read_tsc();
		}

		extern void tsc_init(void);
		extern void mark_tsc_unstable(char *reason);
		extern int unsynchronized_tsc(void);

arch/x86/kvm/x86.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -1455,7 +1455,7 @@ static cycle_t read_tsc(void)
		* but no one has ever seen it happen.
		*/
		rdtsc_barrier();
		ret = (cycle_t)vget_cycles();
		ret = (cycle_t)native_read_tsc();

		last = pvclock_gtod_data.clock.cycle_last;