Re: [PATCH v2] virtio: add VIRTIO_F_NOTIFICATION_DATA feature support

Jason Wang
2023-03-21T02:30:14Z

On Tue, Mar 21, 2023 at 7:21 AM Viktor Prutyanov <viktor@daynix.com> wrote:
>
> According to VirtIO spec v1.2, VIRTIO_F_NOTIFICATION_DATA feature
> indicates that the driver passes extra data along with the queue
> notifications.
>
> In a split queue case, the extra data is 16-bit available index. In a
> packed queue case, the extra data is 1-bit wrap counter and 15-bit
> available index.
>
> Add support for this feature for MMIO and PCI transports. Channel I/O
> transport will not accept this feature.
>
> Signed-off-by: Viktor Prutyanov <viktor@daynix.com>
> ---
>
> v2: reject the feature in virtio_ccw, replace __le32 with u32
>
> drivers/s390/virtio/virtio_ccw.c | 4 +---
> drivers/virtio/virtio_mmio.c | 15 ++++++++++++++-
> drivers/virtio/virtio_pci_common.c | 10 ++++++++++
> drivers/virtio/virtio_pci_common.h | 4 ++++
> drivers/virtio/virtio_pci_legacy.c | 2 +-
> drivers/virtio/virtio_pci_modern.c | 2 +-
> drivers/virtio/virtio_ring.c | 17 +++++++++++++++++
> include/linux/virtio_ring.h | 2 ++
> include/uapi/linux/virtio_config.h | 6 ++++++
> 9 files changed, 56 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/s390/virtio/virtio_ccw.c b/drivers/s390/virtio/virtio_ccw.c
> index a10dbe632ef9..d72a59415527 100644
> --- a/drivers/s390/virtio/virtio_ccw.c
> +++ b/drivers/s390/virtio/virtio_ccw.c
> @@ -789,9 +789,7 @@ static u64 virtio_ccw_get_features(struct virtio_device *vdev)
>
> static void ccw_transport_features(struct virtio_device *vdev)
> {
> - /*
> - * Currently nothing to do here.
> - */
> + __virtio_clear_bit(vdev, VIRTIO_F_NOTIFICATION_DATA);

Is there any restriction that prevents us from implementing
VIRTIO_F_NOTIFICATION_DATA? (Spec seems doesn't limit us from this)

> }
>
> static int virtio_ccw_finalize_features(struct virtio_device *vdev)
> diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c
> index 3ff746e3f24a..0e13da17fe0a 100644
> --- a/drivers/virtio/virtio_mmio.c
> +++ b/drivers/virtio/virtio_mmio.c
> @@ -285,6 +285,19 @@ static bool vm_notify(struct virtqueue *vq)
> return true;
> }
>
> +static bool vm_notify_with_data(struct virtqueue *vq)
> +{
> + struct virtio_mmio_device *vm_dev = to_virtio_mmio_device(vq->vdev);
> + u32 data = vring_fill_notification_data(vq);

Can we move this to the initialization?

Thanks