Re: [PATCH v1 0/8] virtio, vhost: Add VIRTIO_F_NOTIFICATION_DATA support

[Jason Wang]

On Tue, Mar 5, 2024 at 3:46 AM Jonah Palmer <jonah.palmer@oracle.com> wrote:
>
> The goal of these patches are to add support to a variety of virtio and
> vhost devices for the VIRTIO_F_NOTIFICATION_DATA transport feature. This
> feature indicates that a driver will pass extra data (instead of just a
> virtqueue's index) when notifying the corresponding device.
>
> The data passed in by the driver when this feature is enabled varies in
> format depending on if the device is using a split or packed virtqueue
> layout:
>
>  Split VQ
>   - Upper 16 bits: shadow_avail_idx
>   - Lower 16 bits: virtqueue index
>
>  Packed VQ
>   - Upper 16 bits: 1-bit wrap counter & 15-bit shadow_avail_idx
>   - Lower 16 bits: virtqueue index
>
> Also, due to the limitations of ioeventfd not being able to carry the
> extra provided by the driver, ioeventfd is left disabled for any devices
> using this feature.

Is there any method to overcome this? This might help for vhost.

Thanks

>
> A significant aspect of this effort has been to maintain compatibility
> across different backends. As such, the feature is offered by backend
> devices only when supported, with fallback mechanisms where backend
> support is absent.
>
> Jonah Palmer (8):
>   virtio/virtio-pci: Handle extra notification data
>   virtio-pci: Lock ioeventfd state with VIRTIO_F_NOTIFICATION_DATA
>   virtio-mmio: Handle extra notification data
>   virtio-mmio: Lock ioeventfd state with VIRTIO_F_NOTIFICATION_DATA
>   virtio-ccw: Handle extra notification data
>   virtio-ccw: Lock ioeventfd state with VIRTIO_F_NOTIFICATION_DATA
>   vhost/vhost-user: Add VIRTIO_F_NOTIFICATION_DATA to vhost feature bits
>   virtio: Add VIRTIO_F_NOTIFICATION_DATA property definition
>
>  hw/block/vhost-user-blk.c    |  1 +
>  hw/net/vhost_net.c           |  2 ++
>  hw/s390x/s390-virtio-ccw.c   | 16 ++++++++++++----
>  hw/s390x/virtio-ccw.c        |  6 ++++--
>  hw/scsi/vhost-scsi.c         |  1 +
>  hw/scsi/vhost-user-scsi.c    |  1 +
>  hw/virtio/vhost-user-fs.c    |  2 +-
>  hw/virtio/vhost-user-vsock.c |  1 +
>  hw/virtio/virtio-mmio.c      | 15 +++++++++++----
>  hw/virtio/virtio-pci.c       | 16 +++++++++++-----
>  hw/virtio/virtio.c           | 18 ++++++++++++++++++
>  include/hw/virtio/virtio.h   |  5 ++++-
>  net/vhost-vdpa.c             |  1 +
>  13 files changed, 68 insertions(+), 17 deletions(-)
>
> --
> 2.39.3
>