On 2021/1/27 22:20, Alex Williamson wrote: > On Wed, 27 Jan 2021 19:20:06 +0800 > Shenming Lu <lushenm...@huawei.com> wrote: > >> On 2021/1/27 5:36, Alex Williamson wrote: >>> On Wed, 9 Dec 2020 16:09:18 +0800 >>> Shenming Lu <lushenm...@huawei.com> wrote: >>> >>>> In the VFIO VM state change handler, VFIO devices are transitioned >>>> in the _SAVING state, which should keep them from sending interrupts. >>> >>> Is this comment accurate? It's my expectation that _SAVING has no >>> bearing on a device generating interrupts. Interrupt generation must >>> be allowed to continue so long as the device is _RUNNING. Thanks, >>> >> >> To be more accurate, the _RUNNING bit in device_state is cleared in the >> VFIO VM state change handler when stopping the VM. And if the device >> continues >> to send interrupts after this, how can we save the states of device >> interrupts >> in the stop-and-copy phase?... > > Exactly, it's clearing the _RUNNING bit that makes the device stop, > including no longer generating interrupts. Perhaps I incorrectly > inferred "_SAVING state" as referring to the _SAVING bit when you > actually intended: > > * +------- _RESUMING > * |+------ _SAVING > * ||+----- _RUNNING > * ||| > * 000b => Device Stopped, not saving or resuming > * 001b => Device running, which is the default state > -> * 010b => Stop the device & save the device state, stop-and-copy state > > ie. the full state when only _SAVING is set. > > Could we make the comment more clear to avoid this confusion? Thanks, >
OK, sorry for the confusion. I will modify the comment to: In the VFIO VM state change handler when stopping the VM, the _RUNNING bit in device_state is cleared which makes the VFIO device stop, including no longer generating interrupts. Thanks, Shenming > Alex > >>>> Then we can save the pending states of all interrupts in the GIC VM >>>> state change handler (on ARM). >>>> >>>> So we have to set the priority of the VFIO VM state change handler >>>> explicitly (like virtio devices) to ensure it is called before the >>>> GIC's in saving. >>>> >>>> Signed-off-by: Shenming Lu <lushenm...@huawei.com> >>>> Reviewed-by: Kirti Wankhede <kwankh...@nvidia.com> >>>> --- >>>> hw/vfio/migration.c | 3 ++- >>>> 1 file changed, 2 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/hw/vfio/migration.c b/hw/vfio/migration.c >>>> index 3b9de1353a..97ea82b100 100644 >>>> --- a/hw/vfio/migration.c >>>> +++ b/hw/vfio/migration.c >>>> @@ -862,7 +862,8 @@ static int vfio_migration_init(VFIODevice *vbasedev, >>>> register_savevm_live(id, VMSTATE_INSTANCE_ID_ANY, 1, >>>> &savevm_vfio_handlers, >>>> vbasedev); >>>> >>>> - migration->vm_state = >>>> qemu_add_vm_change_state_handler(vfio_vmstate_change, >>>> + migration->vm_state = qdev_add_vm_change_state_handler(vbasedev->dev, >>>> + >>>> vfio_vmstate_change, >>>> vbasedev); >>>> migration->migration_state.notify = vfio_migration_state_notifier; >>>> add_migration_state_change_notifier(&migration->migration_state); >>> >>> . >>> >> > > . >