Marcelo Tosatti wrote:
On Sun, Jan 04, 2009 at 06:14:44PM +0200, Avi Kivity wrote:
Allow clients to request notifications when the guest masks or unmasks a
particular irq line. This complements irq ack notifications, as the guest
will not ack an irq line that is masked.
Currently implemented for the ioapic only.
+
+struct kvm_irq_mask_notifier {
+ void (*func)(struct kvm_irq_mask_notifier *kimn, int masked);
bool masked?
Hey, I'm the bool fanatic!
@@ -128,6 +129,9 @@ static void ioapic_write_indirect(struct kvm_ioapic
*ioapic, u32 val)
ioapic->redirtbl[index].bits |= (u32) val;
ioapic->redirtbl[index].fields.remote_irr = 0;
}
+ mask_after = ioapic->redirtbl[index].fields.mask;
+ if (mask_before != mask_after)
+ kvm_fire_mask_notifiers(ioapic->kvm, index, mask_after);
This can generate "spurious acks", for example:
- inject irq
- guest masks, mask notifier cleans internal state to "acked".
- guest writes EOI
But I suppose thats fine, since PIT (for example) is getting spurious
acks even without mask notifiers and so has to handle them.
If the mask happened for a long time then the guest would expect not to
receive those interrupts. If it happened due to scheduling then we need
to reinject them.
I suppose we could measure descheduled time and correct appropriately.
There previously existed logic that limited the pending count to some
value (10?) so there wouldn't be a stream of interrupts injected into
the guest endlessly.
I expect in most cases, masking of the timer interrupt would not happen
for short periods. You'd use eflags.if or apic.tpr to mask for short
periods.
--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.
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