On Thu, Aug 13, 2009 at 06:11:05AM -0300, Marcelo Tosatti wrote:
> On Wed, Aug 12, 2009 at 03:17:15PM +0300, Gleb Natapov wrote:
> > For device assigned it may cause host hang since ack notifier callback
> > enables host interrupt and guest not necessary cleared interrupt
> > condition in an assigned device. For PIT we should not call ack notifier
> > here since interrupt was not acked by a guest and should be redelivered.
> >
> > Signed-off-by: Gleb Natapov <g...@redhat.com>
> > ---
> > arch/x86/kvm/i8259.c | 16 ----------------
> > 1 files changed, 0 insertions(+), 16 deletions(-)
> >
> > diff --git a/arch/x86/kvm/i8259.c b/arch/x86/kvm/i8259.c
> > index 01f1516..eb2b8b7 100644
> > --- a/arch/x86/kvm/i8259.c
> > +++ b/arch/x86/kvm/i8259.c
> > @@ -225,22 +225,6 @@ int kvm_pic_read_irq(struct kvm *kvm)
> >
> > void kvm_pic_reset(struct kvm_kpic_state *s)
> > {
> > - int irq, irqbase, n;
> > - struct kvm *kvm = s->pics_state->irq_request_opaque;
> > - struct kvm_vcpu *vcpu0 = kvm->bsp_vcpu;
> > -
> > - if (s == &s->pics_state->pics[0])
> > - irqbase = 0;
> > - else
> > - irqbase = 8;
> > -
> > - for (irq = 0; irq < PIC_NUM_PINS/2; irq++) {
> > - if (vcpu0 && kvm_apic_accept_pic_intr(vcpu0))
> > - if (s->irr & (1 << irq) || s->isr & (1 << irq)) {
> > - n = irq + irqbase;
> > - kvm_notify_acked_irq(kvm, SELECT_PIC(n), n);
> > - }
> > - }
> > s->last_irr = 0;
> > s->irr = 0;
> > s->imr = 0;
> > --
> > 1.6.3.3
>
> This used to be necessary to clear pending state from i8254.c
> "irq_acked" logic. I think it'll break it.
This is just a hack then and it does not exists in ioapic so if
it is really needed ioapic+pit combination is broken. But the problem
should be solved inside i8254.c not somewhere else. Setting irq_acked to 1 in
pit_load_count() seems like a right thing to do. Something like
the patch below. Ideally pending should be scaled instead of reset.
Also may be the problem exists because PIC doesn't call mask notifiers?
diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c
index b857ca3..aa7f68e 100644
--- a/arch/x86/kvm/i8254.c
+++ b/arch/x86/kvm/i8254.c
@@ -325,6 +325,9 @@ static void pit_load_count(struct kvm *kvm, int channel,
u32 val)
return;
}
+ atomic_set(&pt->pending, 0);
+ ps->irq_ack = 1;
+
/* Two types of timer
* mode 1 is one shot, mode 2 is period, otherwise del timer */
switch (ps->channels[0].mode) {
--
Gleb.
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