Il 09/09/2014 12:30, Pavel Dovgaluk ha scritto: >> From: Paolo Bonzini [mailto:[email protected]] >> Il 27/08/2014 15:03, Pavel Dovgaluk ha scritto: >>>>> Hmm, probably not. The bug would not be other timers accessing the >>>>> APIC, because that would also call apic_sync_vapic and the only effect >>>>> would be an extra useless synchronization. The bug would happen if the >>>>> APIC is accessed by the CPU before the timer has the occasion to run. >>> Sorry, but I don't understand which problem we will solve with >>> apic_sync_vapic. >> >> Taking inspiration from what KVM does, the fix could be even simpler >> than a change state handler. run_on_cpu functions do not run while the >> VM is stopped, so the following should work: >> >> diff --git a/hw/intc/apic_common.c b/hw/intc/apic_common.c >> index ce3d903..81d1ad7 100644 >> --- a/hw/intc/apic_common.c >> +++ b/hw/intc/apic_common.c >> @@ -91,13 +91,20 @@ void apic_enable_tpr_access_reporting(DeviceState >> *dev, bool enable) >> } >> } >> >> +static void do_apic_enable_vapic(void *data) >> +{ >> + APICCommonState *s = APIC_COMMON(data); >> + APICCommonClass *info = APIC_COMMON_GET_CLASS(s); >> + >> + info->vapic_base_update(s); >> +} >> + >> void apic_enable_vapic(DeviceState *dev, hwaddr paddr) >> { >> APICCommonState *s = APIC_COMMON(dev); >> - APICCommonClass *info = APIC_COMMON_GET_CLASS(s); >> >> s->vapic_paddr = paddr; >> - info->vapic_base_update(s); >> + run_on_cpu(CPU(s->cpu), do_apic_enable_vapic, s); >> } > > I've tried this one and it doesn't work. > do_apic_enable_vapic runs on cpu, at the same time the VM state is loaded. > APIC state still remains broken because of this.
You're right (in fact run_on_cpu is synchronous so the alternative would have been deadlock). A change state handler can work. I'll submit your patches to the migration maintainers, including an alternative fix for this VAPIC problem. Paolo
