From: Andy Lutomirski <[email protected]> __pvclock_read_cycles() had an unnecessary barrier. Get rid of that barrier and clean up the code by just using rdtsc_ordered().
Signed-off-by: Andy Lutomirski <[email protected]> Cc: Denys Vlasenko <[email protected]> Cc: Huang Rui <[email protected]> Cc: John Stultz <[email protected]> Cc: kvm ML <[email protected]> Cc: Len Brown <[email protected]> Cc: Marcelo Tosatti <[email protected]> Cc: Paolo Bonzini <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Radim Krcmar <[email protected]> Cc: Ralf Baechle <[email protected]> Cc: x86-ml <[email protected]> Link: http://lkml.kernel.org/r/678981cc4761fb38a793c217c9cac42503cf3719.1434501121.git.l...@kernel.org Signed-off-by: Borislav Petkov <[email protected]> --- arch/x86/include/asm/pvclock.h | 10 +--------- 1 file changed, 1 insertion(+), 9 deletions(-) diff --git a/arch/x86/include/asm/pvclock.h b/arch/x86/include/asm/pvclock.h index 6084bce345fc..b6c9c9eda914 100644 --- a/arch/x86/include/asm/pvclock.h +++ b/arch/x86/include/asm/pvclock.h @@ -62,7 +62,7 @@ static inline u64 pvclock_scale_delta(u64 delta, u32 mul_frac, int shift) static __always_inline u64 pvclock_get_nsec_offset(const struct pvclock_vcpu_time_info *src) { - u64 delta = rdtsc() - src->tsc_timestamp; + u64 delta = rdtsc_ordered() - src->tsc_timestamp; return pvclock_scale_delta(delta, src->tsc_to_system_mul, src->tsc_shift); } @@ -76,17 +76,9 @@ unsigned __pvclock_read_cycles(const struct pvclock_vcpu_time_info *src, u8 ret_flags; version = src->version; - /* Note: emulated platforms which do not advertise SSE2 support - * result in kvmclock not using the necessary RDTSC barriers. - * Without barriers, it is possible that RDTSC instruction reads from - * the time stamp counter outside rdtsc_barrier protected section - * below, resulting in violation of monotonicity. - */ - rdtsc_barrier(); offset = pvclock_get_nsec_offset(src); ret = src->system_time + offset; ret_flags = src->flags; - rdtsc_barrier(); *cycles = ret; *flags = ret_flags; -- 2.3.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
