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 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 Cc: stable@vger.kernel.org Signed-off-by: Minfei Huang Signed-off-by: Paolo Bonzini --- arch/x86/kernel/pvclock.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'arch/x86/kernel/pvclock.c') diff --git a/arch/x86/kernel/pvclock.c b/arch/x86/kernel/pvclock.c index 99bfc025111d..7f82fe0a6807 100644 --- a/arch/x86/kernel/pvclock.c +++ b/arch/x86/kernel/pvclock.c @@ -66,6 +66,8 @@ u8 pvclock_read_flags(struct pvclock_vcpu_time_info *src) 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 pvclock_vcpu_time_info *src) 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)) { -- cgit v1.2.3 From ed911b43adb889c37a37fa57a995f0b460c633b6 Mon Sep 17 00:00:00 2001 From: Minfei Huang Date: Sat, 28 May 2016 20:27:43 +0800 Subject: pvclock: Get rid of __pvclock_read_cycles in function pvclock_read_flags There is a generic function __pvclock_read_cycles to be used to get both flags and cycles. For function pvclock_read_flags, it's useless to get cycles value. To make this function be more effective, get this variable flags directly in function. Signed-off-by: Minfei Huang Signed-off-by: Paolo Bonzini --- arch/x86/kernel/pvclock.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) (limited to 'arch/x86/kernel/pvclock.c') diff --git a/arch/x86/kernel/pvclock.c b/arch/x86/kernel/pvclock.c index 7f82fe0a6807..06c58ce46762 100644 --- a/arch/x86/kernel/pvclock.c +++ b/arch/x86/kernel/pvclock.c @@ -61,11 +61,14 @@ void pvclock_resume(void) u8 pvclock_read_flags(struct pvclock_vcpu_time_info *src) { unsigned version; - cycle_t ret; u8 flags; do { - version = __pvclock_read_cycles(src, &ret, &flags); + version = src->version; + /* Make the latest version visible */ + smp_rmb(); + + flags = src->flags; /* Make sure that the version double-check is last. */ smp_rmb(); } while ((src->version & 1) || version != src->version); -- cgit v1.2.3