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, 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); > > > > . > > >
