On Wed, Mar 03, 2021, Wanpeng Li wrote: > > Side topic, I think there's a theoretical bug where KVM could inject a spurious > > timer interrupt. If KVM is using hrtimer, the hrtimer expires early due to an > > overzealous timer_advance_ns, and the guest writes MSR_TSCDEADLINE after the > > hrtimer expires but before the vCPU is kicked, then KVM will inject a spurious > > timer IRQ since the premature expiration should have been canceled by the guest's > > WRMSR. > > > > It could also cause KVM to soft hang the guest if the new lapic_timer.tscdeadline > > is written before apic_timer_expired() captures it in expired_tscdeadline. In > > that case, KVM will wait for the new deadline, which could be far in the future. > > The hrtimer_cancel() before setting new lapic_timer.tscdeadline in > kvm_set_lapic_tscdeadline_msr() will wait for the hrtimer callback > function to finish. Could it solve this issue? Aha! Yep, that prevents my theoretical bug. Thanks!
