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/kvm@xxxxxxxxxxxxxxx/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. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
