From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751694AbbFYQri (ORCPT ); Thu, 25 Jun 2015 12:47:38 -0400 Received: from mail.skyhub.de ([78.46.96.112]:38439 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752103AbbFYQog (ORCPT ); Thu, 25 Jun 2015 12:44:36 -0400 From: Borislav Petkov To: Ingo Molnar Cc: LKML Subject: [PATCH 17/19] x86/kvm/tsc: Drop extra barrier and use rdtsc_ordered() in kvmclock Date: Thu, 25 Jun 2015 18:44:11 +0200 Message-Id: <1435250653-30182-18-git-send-email-bp@alien8.de> X-Mailer: git-send-email 2.3.5 In-Reply-To: <1435250653-30182-1-git-send-email-bp@alien8.de> References: <1435250653-30182-1-git-send-email-bp@alien8.de> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Andy Lutomirski __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 Cc: Denys Vlasenko Cc: Huang Rui Cc: John Stultz Cc: kvm ML Cc: Len Brown Cc: Marcelo Tosatti Cc: Paolo Bonzini Cc: Peter Zijlstra Cc: Radim Krcmar Cc: Ralf Baechle Cc: x86-ml Link: http://lkml.kernel.org/r/678981cc4761fb38a793c217c9cac42503cf3719.1434501121.git.luto@kernel.org Signed-off-by: Borislav Petkov --- 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