Re: [RFC PATCH v2 2/3] vfio: Set the priority of the VFIO VM state change handler explicitly

[Alex Williamson]

On Wed, 9 Dec 2020 16:09:18 +0800
Shenming Lu <lushenming@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,

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 <lushenming@huawei.com>
> Reviewed-by: Kirti Wankhede <kwankhede@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);