Commit ca345586 authored by Minfei Huang's avatar Minfei Huang Committed by Greg Kroah-Hartman

pvclock: Add CPU barriers to get correct version value

commit 749d088b 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: 502dfeffSigned-off-by: default avatarMinfei Huang <mnghuan@gmail.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent aab045e9
......@@ -76,6 +76,8 @@ unsigned __pvclock_read_cycles(const struct pvclock_vcpu_time_info *src,
u8 ret_flags;
version = src->version;
/* Make the latest version visible */
smp_rmb();
offset = pvclock_get_nsec_offset(src);
ret = src->system_time + offset;
......
......@@ -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)) {
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment