From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:38861 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755415AbcHCF01 (ORCPT ); Wed, 3 Aug 2016 01:26:27 -0400 Subject: Patch "pvclock: Add CPU barriers to get correct version value" has been added to the 4.4-stable tree To: mnghuan@gmail.com, gregkh@linuxfoundation.org, pbonzini@redhat.com Cc: , From: Date: Wed, 03 Aug 2016 07:24:42 +0200 Message-ID: <1470201882231202@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled pvclock: Add CPU barriers to get correct version value to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: pvclock-add-cpu-barriers-to-get-correct-version-value.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From 749d088b8e7f4b9826ede02b9a043e417fa84aa1 Mon Sep 17 00:00:00 2001 From: Minfei Huang Date: Fri, 27 May 2016 14:17:10 +0800 Subject: pvclock: Add CPU barriers to get correct version value From: Minfei Huang commit 749d088b8e7f4b9826ede02b9a043e417fa84aa1 upstream. Protocol for the "version" fields is: hypervisor raises it (making it uneven) before it starts updating the fields and raises it again (making it even) when it is done. Thus the guest can make sure the time values it got are consistent by checking the version before and after reading them. Add CPU barries after getting version value just like what function vread_pvclock does, because all of callees in this function is inline. Fixes: 502dfeff239e8313bfbe906ca0a1a6827ac8481b Signed-off-by: Minfei Huang Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman --- arch/x86/include/asm/pvclock.h | 2 ++ arch/x86/kernel/pvclock.c | 4 ++++ 2 files changed, 6 insertions(+) --- a/arch/x86/include/asm/pvclock.h +++ b/arch/x86/include/asm/pvclock.h @@ -76,6 +76,8 @@ unsigned __pvclock_read_cycles(const str u8 ret_flags; version = src->version; + /* Make the latest version visible */ + smp_rmb(); offset = pvclock_get_nsec_offset(src); ret = src->system_time + offset; --- a/arch/x86/kernel/pvclock.c +++ b/arch/x86/kernel/pvclock.c @@ -66,6 +66,8 @@ u8 pvclock_read_flags(struct pvclock_vcp do { version = __pvclock_read_cycles(src, &ret, &flags); + /* Make sure that the version double-check is last. */ + smp_rmb(); } while ((src->version & 1) || version != src->version); return flags & valid_flags; @@ -80,6 +82,8 @@ cycle_t pvclock_clocksource_read(struct do { version = __pvclock_read_cycles(src, &ret, &flags); + /* Make sure that the version double-check is last. */ + smp_rmb(); } while ((src->version & 1) || version != src->version); if (unlikely((flags & PVCLOCK_GUEST_STOPPED) != 0)) { Patches currently in stable-queue which might be from mnghuan@gmail.com are queue-4.4/pvclock-add-cpu-barriers-to-get-correct-version-value.patch