Re: [PATCH v9 10/14] vfio/migration: Implement VFIO migration protocol v2

[Alex Williamson]

On Mon, 6 Feb 2023 14:31:33 +0200
Avihai Horon <avihaih@nvidia.com> wrote:
> @@ -523,6 +745,41 @@ static int vfio_save_iterate(QEMUFile *f, void *opaque)
>      return 0;
>  }
>  
> +static int vfio_save_complete_precopy(QEMUFile *f, void *opaque)
> +{
> +    VFIODevice *vbasedev = opaque;
> +    enum vfio_device_mig_state recover_state;
> +    int ret;
> +
> +    /* We reach here with device state STOP only */
> +    recover_state = VFIO_DEVICE_STATE_STOP;

Why do we need to put this in a local variable?

> +    ret = vfio_migration_set_state(vbasedev, VFIO_DEVICE_STATE_STOP_COPY,
> +                                   recover_state);
> +    if (ret) {
> +        return ret;
> +    }
> +
> +    do {
> +        ret = vfio_save_block(f, vbasedev->migration);
> +        if (ret < 0) {
> +            return ret;
> +        }
> +    } while (!ret);
> +
> +    qemu_put_be64(f, VFIO_MIG_FLAG_END_OF_STATE);
> +    ret = qemu_file_get_error(f);
> +    if (ret) {
> +        return ret;
> +    }
> +
> +    recover_state = VFIO_DEVICE_STATE_ERROR;

IIRC, the ERROR state is not reachable as a user directed state.  I
suppose passing it as the recovery state guarantees a device reset when
it fails, but if that's the intention it should be documented with a
comment to explain so (and vfio_migration_set_state() should not bother
trying to use it as a recovery state).

> +    ret = vfio_migration_set_state(vbasedev, VFIO_DEVICE_STATE_STOP,
> +                                   recover_state);
> +    trace_vfio_save_complete_precopy(vbasedev->name, ret);
> +
> +    return ret;
> +}
> +
>  static int vfio_v1_save_complete_precopy(QEMUFile *f, void *opaque)
>  {
>      VFIODevice *vbasedev = opaque;
...
> @@ -769,12 +1087,17 @@ static void vfio_migration_state_notifier(Notifier 
> *notifier, void *data)
>      case MIGRATION_STATUS_CANCELLED:
>      case MIGRATION_STATUS_FAILED:
>          bytes_transferred = 0;
> -        ret = vfio_migration_v1_set_state(vbasedev,
> -                                          ~(VFIO_DEVICE_STATE_V1_SAVING |
> -                                            VFIO_DEVICE_STATE_V1_RESUMING),
> -                                          VFIO_DEVICE_STATE_V1_RUNNING);
> -        if (ret) {
> -            error_report("%s: Failed to set state RUNNING", vbasedev->name);
> +        if (migration->v2) {
> +            vfio_migration_set_state(vbasedev, VFIO_DEVICE_STATE_RUNNING,
> +                                     VFIO_DEVICE_STATE_ERROR);

Same here.  Thanks,

Alex

> +        } else {
> +            ret = vfio_migration_v1_set_state(vbasedev,
> +                                              ~(VFIO_DEVICE_STATE_V1_SAVING |
> +                                                
> VFIO_DEVICE_STATE_V1_RESUMING),
> +                                              VFIO_DEVICE_STATE_V1_RUNNING);
> +            if (ret) {
> +                error_report("%s: Failed to set state RUNNING", 
> vbasedev->name);
> +            }
>          }
>      }
>  }