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Commit b4a2f5e7 authored by Gleb Natapov's avatar Gleb Natapov Committed by Avi Kivity
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KVM: Avoid redelivery of edge interrupt before next edge 



The check for an edge is broken in current ioapic code. ioapic->irr is
cleared on each edge interrupt by ioapic_service() and this makes
old_irr != ioapic->irr condition in kvm_ioapic_set_irq() to be always
true. The patch fixes the code to properly recognise edge.

Some HW emulation calls set_irq() without level change. If each such
call is propagated to an OS it may confuse a device driver. This is the
case with keyboard device emulation and Windows XP x64  installer on SMP VM.
Each keystroke produce two interrupts (down/up) one interrupt is
submitted to CPU0 and another to CPU1. This confuses Windows somehow
and it ignores keystrokes.

Signed-off-by: default avatarGleb Natapov <gleb@redhat.com>
Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
parent 53a27b39

virt/kvm/ioapic.c

+5 −5
Original line number Diff line number Diff line
@@ -95,8 +95,6 @@ static int ioapic_service(struct kvm_ioapic *ioapic, unsigned int idx) 
		if (injected && pent->fields.trig_mode == IOAPIC_LEVEL_TRIG)

			pent->fields.remote_irr = 1;

	}

	if (!pent->fields.trig_mode)

		ioapic->irr &= ~(1 << idx);



	return injected;

}
@@ -136,7 +134,8 @@ static void ioapic_write_indirect(struct kvm_ioapic *ioapic, u32 val) 
		mask_after = ioapic->redirtbl[index].fields.mask;

		if (mask_before != mask_after)

			kvm_fire_mask_notifiers(ioapic->kvm, index, mask_after);

		if (ioapic->irr & (1 << index))

		if (ioapic->redirtbl[index].fields.trig_mode == IOAPIC_LEVEL_TRIG

		    && ioapic->irr & (1 << index))

			ioapic_service(ioapic, index);

		break;

	}
@@ -184,9 +183,10 @@ int kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int level) 
		if (!level)

			ioapic->irr &= ~mask;

		else {

			int edge = (entry.fields.trig_mode == IOAPIC_EDGE_TRIG);

			ioapic->irr |= mask;

			if ((!entry.fields.trig_mode && old_irr != ioapic->irr)

			    || !entry.fields.remote_irr)

			if ((edge && old_irr != ioapic->irr) ||

			    (!edge && !entry.fields.remote_irr))

				ret = ioapic_service(ioapic, irq);

		}

	}