Messages in this thread | | | Date | Wed, 15 Feb 2012 12:49:45 +0200 | From | Avi Kivity <> | Subject | Re: [PATCH] BUG in pv_clock when overflow condition is detected |
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On 02/13/2012 08:20 PM, Igor Mammedov wrote: > BUG when overflow occurs at pvclock.c:pvclock_get_nsec_offset > > u64 delta = native_read_tsc() - shadow->tsc_timestamp; > > this might happen at an attempt to read an uninitialized yet clock. > It won't prevent stalls and hangs but at least it won't do it silently. > > Signed-off-by: Igor Mammedov <imammedo@redhat.com> > --- > arch/x86/kernel/pvclock.c | 5 ++++- > 1 files changed, 4 insertions(+), 1 deletions(-) > > diff --git a/arch/x86/kernel/pvclock.c b/arch/x86/kernel/pvclock.c > index 42eb330..35a6190 100644 > --- a/arch/x86/kernel/pvclock.c > +++ b/arch/x86/kernel/pvclock.c > @@ -43,7 +43,10 @@ void pvclock_set_flags(u8 flags) > > static u64 pvclock_get_nsec_offset(struct pvclock_shadow_time *shadow) > { > - u64 delta = native_read_tsc() - shadow->tsc_timestamp; > + u64 delta; > + u64 tsc = native_read_tsc(); > + BUG_ON(tsc < shadow->tsc_timestamp); > + delta = tsc - shadow->tsc_timestamp; > return pvclock_scale_delta(delta, shadow->tsc_to_nsec_mul, > shadow->tsc_shift);
Maybe a WARN_ON_ONCE()? Otherwise a relatively minor hypervisor bug can kill the guest.
-- error compiling committee.c: too many arguments to function
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