On Thu, Feb 03, 2011 at 11:11:23AM +0100, Jan Kiszka wrote:
> On 2011-02-03 11:04, Marcelo Tosatti wrote:
> > On Thu, Feb 03, 2011 at 10:32:25AM +0100, Jan Kiszka wrote:
> >> On 2011-02-03 09:18, Avi Kivity wrote:
> >>> On 02/02/2011 05:52 PM, Jan Kiszka wrote:
> >>>>>>
> >>>>> If there is no problem in the logic of this commit (and I do not see
> >>>>> one yet) then we somewhere miss kicking vcpu when interrupt, that
> >>>>> should be
> >>>>> handled, arrives?
> >>>>
> >>>> I'm not yet confident about the logic of the kernel patch: mov to cr8 is
> >>>> serializing. If the guest raises the tpr and then signals this with a
> >>>> succeeding, non vm-exiting instruction to the other vcpus, one of those
> >>>> could inject an interrupt with a higher priority than the previous tpr,
> >>>> but a lower one than current tpr. QEMU user space would accept this
> >>>> interrupt - and would likely surprise the guest. Do I miss something?
> >>>
> >>> apic_get_interrupt() is only called from the vcpu thread, so it should
> >>> see a correct tpr.
> >>>
> >>> The only difference I can see with the patch is that we may issue a
> >>> spurious cpu_interrupt(). But that shouldn't do anything bad, should it?
> >>
> >> I tested this yesterday, and it doesn't confuse Windows. It actually
> >> receives quite a few spurious IRQs in normal operation, w/ or w/o the
> >> kernel's tpr optimization.
> >
> > http://www.mail-archive.com/[email protected]/msg41681.html
>
> Don't get the scenario yet: We do not inject (or set isr) over the
> context of apic_set_irq caller.
>
> >
> > tpr of a vcpu should always be inspected in vcpu context, instead of
> > iothread context?
>
> Maybe this is true for the in-kernel model, but I don't see the issue
> (anymore) for the way user space works.
>
With patch below I can boot Windows7.
diff --git a/hw/apic.c b/hw/apic.c
index 146deca..fdcac88 100644
--- a/hw/apic.c
+++ b/hw/apic.c
@@ -600,7 +600,7 @@ int apic_get_interrupt(DeviceState *d)
intno = get_highest_priority_int(s->irr);
if (intno < 0)
return -1;
- if (s->tpr && intno <= s->tpr)
+ if ((s->tpr >> 4) && (intno >> 4) <= (s->tpr >> 4))
return s->spurious_vec & 0xff;
reset_bit(s->irr, intno);
set_bit(s->isr, intno);
--
Gleb.
