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

[Eugenio Perez Martin]

Hi Wentao / Rick / Xinying Yu,

Would it work for you to test this series on your use cases, so we
make sure everything works as expected?

Thanks!

On Fri, Mar 1, 2024 at 2:44 PM 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: last_avail_idx
>   - Lower 16 bits: virtqueue index
>
>  Packed VQ
>   - Upper 16 bits: 1-bit wrap counter & 15-bit last_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.
>
> 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.
>

Hi Wentao,