raspi/linux
1
0
Fork 1
mirror of https://github.com/raspberrypi/linux.git synced 2025-12-06 10:00:17 +00:00
Code Issues Projects Releases Wiki Activity

pvclock: Add CPU barriers to get correct version value

Browse Source 
commit 749d088b8e 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: 502dfeff23
Signed-off-by: Minfei Huang <mnghuan@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Minfei Huang
2016-05-27 14:17:10 +08:00
committed by Greg Kroah-Hartman
parent aab045e9a9
commit ca3455867e
2 changed files with 6 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
arch/x86/include/asm/pvclock.h
View File

@@ -76,6 +76,8 @@ unsigned __pvclock_read_cycles(const struct pvclock_vcpu_time_info *src,
u8 ret_flags; u8 ret_flags;
version = src->version; version = src->version;
/* Make the latest version visible */
smp_rmb();
offset = pvclock_get_nsec_offset(src); offset = pvclock_get_nsec_offset(src);
ret = src->system_time + offset; ret = src->system_time + offset;

4
arch/x86/kernel/pvclock.c
View File

@@ -66,6 +66,8 @@ u8 pvclock_read_flags(struct pvclock_vcpu_time_info *src)
do { do {
version = __pvclock_read_cycles(src, &ret, &flags); 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); } while ((src->version & 1) || version != src->version);
return flags & valid_flags; return flags & valid_flags;
@@ -80,6 +82,8 @@ cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src)
do { do {
version = __pvclock_read_cycles(src, &ret, &flags); 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); } while ((src->version & 1) || version != src->version);
if (unlikely((flags & PVCLOCK_GUEST_STOPPED) != 0)) { if (unlikely((flags & PVCLOCK_GUEST_STOPPED) != 0)) {