Re: qemu-kvm requires apic initialized before vcpu main loop

[Marcelo Tosatti <mtosatti@redhat.com>]

On Wed, Dec 09, 2009 at 07:23:38PM +0100, Jan Kiszka wrote:
> Marcelo Tosatti wrote:
> > Otherwise a zero apic base is loaded into KVM, which results
> > in interrupts being lost until a proper apic base with enabled 
> > bit set is loaded.
> > 
> > Fixes WinXP migration in qemu-kvm origin/next.
> > 
> > Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
> > 
> > diff --git a/hw/apic.c b/hw/apic.c
> > index 627ff98..45a4d2b 100644
> > --- a/hw/apic.c
> > +++ b/hw/apic.c
> > @@ -1131,6 +1131,11 @@ int apic_init(CPUState *env)
> >      vmstate_register(s->idx, &vmstate_apic, s);
> >      qemu_register_reset(apic_reset, s);
> >  
> > +    /* apic_reset must be called before the vcpu threads are initialized and load 
> > +     * registers, in qemu-kvm.
> > +     */
> > +    apic_reset(s);
> > +
> >      local_apics[s->idx] = s;
> >      return 0;
> >  }
> 
> Heals the issue I saw with Win2003 Server as well.
> 
> Looks all a bit messy though. Hope we can establish a more regular and
> less fragile model on the midterm. 

Yes, its a house of cards which falls all the time :(

> I wonder if it wouldn't be better to do write-back of the local APIC
> state along with the register state on vmrun (and only there!).
> The same would apply to things like mpstate, TSC MSR, or the guest
> debugging state. The reset/vmloading/hw-emulation code would only
> declare what kind of write-back it wishes: register state only,
> partial (excluding everything that touches continuously running
> timers), full. Well, basically the model I suggested for proper
> mpstate write-back, just even more generalized.
> 
> Jan