On Wed, Feb 2, 2011 at 10:51 AM, Glauber Costa <glom...@redhat.com> wrote: > Avi noticed that we have to use guest's value for the version field, > instead of keeping track of it ourselves. If we don't do that, > the following situation can arise: > > vcpu->arch.hv_clock.version is initialized to zero. > Guest reads version (result: 2) > Guest starts reading data > Live migration; vcpu->arch.hv_clock.version is zeroed > Steal time update; vcpu->arch.hv_clock.version += 2; write to guest > Guest continues reading data > Guest reads version (result: 2) Please ignore it. I did test this patch but appearently used the wrong module, and it tricked me this version is obviously wrong.
> > Signed-off-by: Glauber Costa <glom...@redhat.com> > CC: Avi Kivity <a...@redhat.com> > --- > arch/x86/kvm/x86.c | 9 ++++++--- > 1 files changed, 6 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index c39ab4a..7fdc84a 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -1151,15 +1151,18 @@ static int kvm_guest_time_update(struct kvm_vcpu *v) > vcpu->last_guest_tsc = tsc_timestamp; > vcpu->hv_clock.flags = 0; > > + shared_kaddr = kmap_atomic(vcpu->time_page, KM_USER0); > + > /* > * The interface expects us to write an even number signaling that the > * update is finished. Since the guest won't see the intermediate > - * state, we just increase by 2 at the end. > + * state, we just increase by 2 at the end. We use the guest's value > as > + * a basis to make it migration-safe. > */ > + memcpy(&vcpu->hv_clock, shared_kaddr + vcpu->time_offset, > + sizeof(vcpu->hv_clock)); > vcpu->hv_clock.version += 2; > > - shared_kaddr = kmap_atomic(vcpu->time_page, KM_USER0); > - > memcpy(shared_kaddr + vcpu->time_offset, &vcpu->hv_clock, > sizeof(vcpu->hv_clock)); > > -- > 1.7.2.3 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > -- Sent from my Atari. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
