On Tue, Aug 29, 2017 at 04:07:59PM -0400, Willem de Bruijn wrote:
> From: Willem de Bruijn <willemb@xxxxxxxxxx>
>
> Implement a mechanism to signal that a virtio device implements the
> VIRTIO_CONFIG_S_NEEDS_RESET command.
>
> Testing for VIRTIO_CONFIG_S_NEEDS_RESET support by issuing the request
> and verifying the reset state would require an expensive state change.
>
> To avoid that, add a status bit to the feature register used during
> feature negotiation between host and guest.
>
> Set the bit for virtio-net, which supports the feature.
>
> Signed-off-by: Willem de Bruijn <willemb@xxxxxxxxxx>
All virtio 1 devices have the reset feature so maybe guest does
not need this flag. Does device need it? Does device really
care that guest can't recover?
> ---
> drivers/net/virtio_net.c | 2 ++
> include/uapi/linux/virtio_config.h | 3 +++
> 2 files changed, 5 insertions(+)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index 5e349226f7c1..15483a982106 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -2801,12 +2801,14 @@ static struct virtio_device_id id_table[] = {
>
> static unsigned int features[] = {
> VIRTNET_FEATURES,
> + VIRTIO_F_CAN_RESET,
> };
>
> static unsigned int features_legacy[] = {
> VIRTNET_FEATURES,
> VIRTIO_NET_F_GSO,
> VIRTIO_F_ANY_LAYOUT,
> + VIRTIO_F_CAN_RESET,
> };
>
> static struct virtio_driver virtio_net_driver = {
> diff --git a/include/uapi/linux/virtio_config.h b/include/uapi/linux/virtio_config.h
> index 308e2096291f..726be44a04d3 100644
> --- a/include/uapi/linux/virtio_config.h
> +++ b/include/uapi/linux/virtio_config.h
> @@ -56,6 +56,9 @@
> * suppressed them? */
> #define VIRTIO_F_NOTIFY_ON_EMPTY 24
>
> +/* Driver supports the VIRTIO_CONFIG_S_NEEDS_RESET command */
> +#define VIRTIO_F_CAN_RESET 25
> +
> /* Can the device handle any descriptor layout? */
> #define VIRTIO_F_ANY_LAYOUT 27
> #endif /* VIRTIO_CONFIG_NO_LEGACY */
> --
> 2.14.1.342.g6490525c54-goog
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