KVM: Avoid redelivery of edge interrupt before next edge (b4a2f5e7) · Commits · 戴 / test

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:

Gleb Natapov <gleb@redhat.com> Signed-off-by:

Avi Kivity <avi@redhat.com>

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);
		}
		}

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