Messages in this thread Patch in this message | | | From | Igor Mammedov <> | Subject | [PATCH 1/2] x86: kvmclock: zero initialize pvclock shared memory area | Date | Fri, 21 Jun 2013 11:01:20 +0200 |
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Since commit: 7069ed6 x86: kvmclock: allocate pvclock shared memory area
kernel might hung in pvclock_clocksource_read() due to uninitialized memory might contain odd version value in following cycle:
do { version = __pvclock_read_cycles(src, &ret, &flags); } while ((src->version & 1) || version != src->version);
if secondary kvmclock is accessed before it's registered with kvm.
Additionally before regression was introduced users of pre-cpu hv_clock were relying on variable being zero initialized, and 7069ed6 breaks this assumption for usage of: hv_clock.migrate_count which could be populated with random garbage now.
Clearing garbage in pvclock shared memory area right after it's allocated helps to avoid these issues.
Signed-off-by: Igor Mammedov <imammedo@redhat.com> --- arch/x86/kernel/kvmclock.c | 1 + 1 files changed, 1 insertions(+), 0 deletions(-)
diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c index d2c3812..3dd37eb 100644 --- a/arch/x86/kernel/kvmclock.c +++ b/arch/x86/kernel/kvmclock.c @@ -242,6 +242,7 @@ void __init kvmclock_init(void) if (!mem) return; hv_clock = __va(mem); + memset(hv_clock, 0, size); if (kvm_register_clock("boot clock")) { hv_clock = NULL; -- 1.7.1
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