Re: [Qemu-devel] KVM: Windows 64-bit troubles with user space irqchip

[Avi Kivity <avi@redhat.com>]

On 02/02/2011 04:52 PM, Jan Kiszka wrote:
> On 2011-02-02 15:43, Jan Kiszka wrote:
> >  On 2011-02-02 15:35, Avi Kivity wrote:
> >>  On 02/02/2011 04:30 PM, Jan Kiszka wrote:
> >>>  On 2011-02-02 14:05, Avi Kivity wrote:
> >>>>   On 02/02/2011 02:50 PM, Jan Kiszka wrote:
> >>>>>>>
> >>>>>>    Opps, -smp 1. With -smp 2 it boot almost completely and then hangs.
> >>>>>
> >>>>>   Ah, good (or not good). With Windows 2003 Server, I actually get a Blue
> >>>>>   Screen (Stop 0x000000b8).
> >>>>
> >>>>   Userspace APIC is broken since it may run with an outdated cr8, does
> >>>>   reverting 27a4f7976d5 help?
> >>>
> >>>  Can you elaborate on what is broken? The way hw/apic.c maintains the
> >>>  tpr? Would it make sense to compare this against the in-kernel model? Or
> >>>  do you mean something else?
> >>
> >>  The problem, IIRC, was that we look up the TPR but it may already have
> >>  been changed by the running vcpu.  Not 100% sure.
> >>
> >>  If that is indeed the problem then the fix would be to process the APIC
> >>  in vcpu context (which is what the kernel does - we set a bit in the IRR
> >>  and all further processing is synchronous).
> >
> >  You mean: user space changes the tpr value while the vcpu is in KVM_RUN,
> >  then we return from the kernel and overwrite the tpr in the apic with
> >  the vcpu's view, right?
>
> Hmm, probably rather that there is a discrepancy between tpr and irr.
> The latter is changed asynchronously /wrt to the vcpu, the former /wrt
> the user space device model.

And yet, both are synchronized via qemu_mutex.  So we're still missing 
something in this picture.

> Run apic_set_irq on the vcpu?

static void apic_set_irq(APICState *s, int vector_num, int trigger_mode)
{
     apic_irq_delivered += !get_bit(s->irr, vector_num);

     trace_apic_set_irq(apic_irq_delivered);

     set_bit(s->irr, vector_num);

This is even more async with kernel irqchip

     if (trigger_mode)
         set_bit(s->tmr, vector_num);
     else
         reset_bit(s->tmr, vector_num);

This is protected by qemu_mutex

     apic_update_irq(s);

This will be run the next time the vcpu exits, via apic_get_interrupt().

}

Did you check whether reverting that commit helps?

-- 
error compiling committee.c: too many arguments to function