Alexander Larsson reported a migration bug where after migration the Windows virtio-serial driver was not able to read anymore, not seeing the data from the host. He debugged it and noticed that after migration the virtio-serial driver ddid not respond to any irqs. During restore we virtio_notify() on the serial device, which eventually raises the pci irq level to 1. However, the driver is never notified and thus never responds to this by reading the VIRTIO_PCI_ISR, so the irq level is never cleared, and all later virtio_notify() do nothing. A simplified reproducer (that doesn't hang Linux, but shows the message) is to start the VM without a backend for the virtserialport, and to resume it with a backend, for example $ qemu-system-x86_64 -device virtio-serial-pci -device virtserialport test.img --enable-kvm -m 512 $ qemu-system-x86_64 -device virtio-serial-pci -chardev stdio,id=vs0 -device virtserialport,chardev=vs0 test.img --enable-kvm -m 512 -incoming 'exec:cat foo.ckp' In fact, interrupt injection fails and reports correctly "KVM: injection failed, MSI lost". The reason for the failure is that the LAPIC doesn't think it's enabled, which in turn is because the LAPIC is restored after the CPU and, when restoring the CPU, a dummy post-reset state is passed to the in-kernel APIC. The fix for this is to let the APIC update its in-kernel counterpart after loading. Patches 1 and 2 change the hard-coded references to kvm_get_apic_state and kvm_put_apic_state to methods in APICCommonClass. This is useful because it lets APICCommon force an update of the in-kernel state after load (patch 3). Patches 4 and 5 similarly add get/put methods to the IOAPIC hierarchy, which replace pre_save/post_load. Paolo Paolo Bonzini (5): kvm: move KVM_GET_LAPIC/KVM_SET_LAPIC to hw/kvm/apic.c apic: add get/put methods apic: always update the in-kernel status after loading ioapic: change pre_save/post_load methods to get/put ioapic: unify reset callbacks hw/apic.h | 2 + hw/apic_common.c | 33 ++++++++++++++++++++ hw/apic_internal.h | 2 + hw/ioapic.c | 2 - hw/ioapic_common.c | 42 +++++++++++++++++--------- hw/ioapic_internal.h | 6 +-- hw/kvm/apic.c | 80 ++++++++++++++++++++++++++++---------------------- hw/kvm/ioapic.c | 13 +------- kvm.h | 3 -- target-i386/kvm.c | 34 +-------------------- 10 files changed, 115 insertions(+), 102 deletions(-) -- 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
