Re: [Qemu-devel] [PATCH 06/12] kvmvapic: fixing loading vmstate

["Pavel Dovgaluk" <Pavel.Dovgaluk@ispras.ru>]

> From: Paolo Bonzini [mailto:pbonzini@redhat.com]
> 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.

Pavel Dovgalyuk