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@xxxxxxxxxx>
---
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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