Re: [Qemu-devel] [RFC v8.1 07/13] vfio: add check for vfio devices which enable aer should support bus reset

[Alex Williamson <alex.williamson@redhat.com>]

On Wed, 2015-05-27 at 10:46 +0800, Chen Fan wrote:
> Signed-off-by: Chen Fan <chen.fan.fnst@cn.fujitsu.com>
> ---
>  hw/vfio/pci.c | 32 ++++++++++++++++++++++++++++++++
>  1 file changed, 32 insertions(+)
> 
> diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c
> index 5934fd7..91ad9ad 100644
> --- a/hw/vfio/pci.c
> +++ b/hw/vfio/pci.c
> @@ -3801,6 +3801,33 @@ out:
>      g_free(info);
>  }
>  
> +static void vfio_pci_machine_done_notify(Notifier *notifier, void *unused)
> +{
> +    VFIOGroup *group;
> +    VFIODevice *vbasedev;
> +    VFIOPCIDevice *vdev;
> +
> +    /* Check All support AER devices if has bus reset capability */
> +    QLIST_FOREACH(group, &vfio_group_list, next) {
> +        QLIST_FOREACH(vbasedev, &group->device_list, next) {
> +            vdev = container_of(vbasedev, VFIOPCIDevice, vbasedev);
> +            if (vdev->features & VFIO_FEATURE_ENABLE_AER) {
> +                vfio_check_host_bus_reset(vdev);
> +                if (!vdev->has_bus_reset) {
> +                    error_report("vfio: Cannot enable AER for device %s, "
> +                                 "which is not support host bus reset.",
> +                                 vdev->vbasedev.name);
> +                    exit(1);
> +                }
> +            }
> +        }
> +    }
> +}
> +
> +static Notifier machine_notifier = {
> +    .notify = vfio_pci_machine_done_notify,
> +};
> +
>  static int vfio_initfn(PCIDevice *pdev)
>  {
>      VFIOPCIDevice *vdev = DO_UPCAST(VFIOPCIDevice, pdev, pdev);
> @@ -4086,6 +4113,11 @@ static const TypeInfo vfio_pci_dev_info = {
>  static void register_vfio_pci_dev_type(void)
>  {
>      type_register_static(&vfio_pci_dev_info);
> +    /*
> +     * Register notifier when machine init is done, since we need
> +     * check the configration manner after all vfio devices are inited.
> +     */
> +    qemu_add_machine_init_done_notifier(&machine_notifier);
>  }
>  
>  type_init(register_vfio_pci_dev_type)

I don't see what we're gaining by waiting until after machine init done
to test everything.  It makes cold-plug a different case than hot-plug,
which makes things error prone.