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authorAndy Lutomirski <luto@kernel.org>2015-06-25 19:44:11 +0300
committerIngo Molnar <mingo@kernel.org>2015-07-06 16:23:30 +0300
commit502dfeff239e8313bfbe906ca0a1a6827ac8481b (patch)
tree00e069166b5fb7e115b52d1b9d5d9e9d3c8b3e20 /arch/x86/include/asm/pvclock.h
parent27c634054a3155e1d9a02f0e362e4f4ff8d28ee7 (diff)
downloadlinux-502dfeff239e8313bfbe906ca0a1a6827ac8481b.tar.xz
x86/asm/tsc, x86/kvm: Drop open-coded barrier and use rdtsc_ordered() in kvmclock
__pvclock_read_cycles() used to have two barriers, one of which was unnecessary, which got removed after an initial version of this patch was sent. But the barrier is still open-coded unnecessarily - get rid of that barrier and clean up the code by just using rdtsc_ordered(). 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: Marcelo Tosatti <mtosatti@redhat.com> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Radim Krcmar <rkrcmar@redhat.com> 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/678981cc4761fb38a793c217c9cac42503cf3719.1434501121.git.luto@kernel.org [ Ported it to v4.2-rc1. ] Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/include/asm/pvclock.h')
-rw-r--r--arch/x86/include/asm/pvclock.h10
1 files changed, 2 insertions, 8 deletions
diff --git a/arch/x86/include/asm/pvclock.h b/arch/x86/include/asm/pvclock.h
index 5c490db62e32..7a6bed5c08bc 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);
}
@@ -76,13 +76,7 @@ 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;