2014-03-21 10:27+0100, Paolo Bonzini: > Unlike the old qemu-kvm, which really never did that, with new QEMU > it is for some reason somewhat likely to migrate a VM with a nonzero > IRR in the ioapic. In the case of ISA edge-triggered interrupts, > this represents an interrupt that has not left the IOAPIC, which would > be okay but it is not handled right by KVM_SET_IRQCHIP. Because the > interrupt is never injected, the guest never acknowledges it, the host > never deasserts the pin and new interrupts are dropped. > > There are two problems to solve. > > The obvious one is that interrupts are not reinjected upon KVM_SET_IRQCHIP, > which is taken care of by patches 3-4. > > The second is that right now the IRR value depends on the falling edge > of the interrupt (as passed by the userspace via kvm_ioapic_set_irq). > This is unnecessary, and may lead to spurious reinjection in the > destination of migration; instead, we can clear the (internal-only) > IRR bit as soon as the interrupt leaves the IOAPIC. This is done by > patch 2, which patch 1 prepares for. > > This fixes migration of Windows guests without HPET. Please review. > > Paolo > > v1->v2: > more comments in patch 3 > change argument name in patch 3 from level to irq_level > use IOAPIC_NUM_PINS in patch 4 as a limit to for_each_set_bit > remove debug printk in patch 4 Nice solution to a tricky problem, Reviewed-by: Radim Krčmář <rkrcmar@xxxxxxxxxx> > Paolo Bonzini (4): > KVM: ioapic: merge ioapic_deliver into ioapic_service > KVM: ioapic: clear IRR for edge-triggered interrupts at delivery > KVM: ioapic: extract body of kvm_ioapic_set_irq > KVM: ioapic: reinject pending interrupts on KVM_SET_IRQCHIP > > virt/kvm/ioapic.c | 107 +++++++++++++++++++++++++++++++++++------------------- > 1 file changed, 69 insertions(+), 38 deletions(-) > > -- > 1.8.3.1 > > -- > 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 -- 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
