On Thu, Jul 20, 2017 at 11:38:19AM +0300, Konstantin Khorenko wrote: > Need it in update 5?
That's up to Den to decide. The livelock is only triggerable with one-shot SynIC timers; none of our regular guests uses them (Windows uses periodic timers, Linux does use one-shot timers but needs to be started with hyperv on and kvm off which doesn't happen in normal use). > Any bug id? The problem was noticed in a special scenario on my dev machine with the mainstream kernel so I didn't bother to file a bug. I'm about to post the patch to the KVM list so you'll have the master commit id once (if) it's merged. Roman. > > -- > Best regards, > > Konstantin Khorenko, > Virtuozzo Linux Kernel Team > > On 07/19/2017 08:31 PM, Roman Kagan wrote: > > If the SynIC timer message delivery fails due to SINT message slot being > > busy, there's no point to attempt starting the timer again until we're > > notified of the slot being released by the guest (via EOM or EOI). > > > > Even worse, when a oneshot timer fails to deliver its message, its > > re-arming with an expiration time in the past leads to immediate retry > > of the delivery, without ever letting the guest vcpu to run and release > > the slot, which results in a livelock. > > > > To avoid that, only start the timer when there's no timer message > > pending delivery. When the guest releases the slot, the processing is > > resumed so the timer will be started then. > > > > Signed-off-by: Roman Kagan <rka...@virtuozzo.com> > > --- > > arch/x86/kvm/hyperv.c | 7 ++++--- > > 1 file changed, 4 insertions(+), 3 deletions(-) > > > > diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c > > index c8efdce3e702..ab9501c2f32c 100644 > > --- a/arch/x86/kvm/hyperv.c > > +++ b/arch/x86/kvm/hyperv.c > > @@ -632,9 +632,10 @@ void kvm_hv_process_stimers(struct kvm_vcpu *vcpu) > > } > > > > if ((stimer->config & HV_STIMER_ENABLE) && > > - stimer->count) > > - stimer_start(stimer); > > - else > > + stimer->count) { > > + if (!stimer->msg_pending) > > + stimer_start(stimer); > > + } else > > stimer_cleanup(stimer); > > } > > } > > _______________________________________________ Devel mailing list Devel@openvz.org https://lists.openvz.org/mailman/listinfo/devel