Re: [PATCH v3 for 9.1 1/6] virtio/virtio-pci: Handle extra notification data

[Eugenio Perez Martin]

On Fri, Mar 15, 2024 at 5:57 PM Jonah Palmer <jonah.palmer@oracle.com> wrote:
>
> Add support to virtio-pci devices for handling the extra data sent
> from the driver to the device when the VIRTIO_F_NOTIFICATION_DATA
> transport feature has been negotiated.
>
> The extra data that's passed to the virtio-pci device when this
> feature is enabled varies depending on the device's virtqueue
> layout.
>
> In a split virtqueue layout, this data includes:
>  - upper 16 bits: shadow_avail_idx
>  - lower 16 bits: virtqueue index
>
> In a packed virtqueue layout, this data includes:
>  - upper 16 bits: 1-bit wrap counter & 15-bit shadow_avail_idx
>  - lower 16 bits: virtqueue index
>

Reviewed-by: Eugenio Pérez <eperezma@redhat.com>

Thanks!

> Signed-off-by: Jonah Palmer <jonah.palmer@oracle.com>
> ---
>  hw/virtio/virtio-pci.c     | 11 ++++++++---
>  hw/virtio/virtio.c         | 18 ++++++++++++++++++
>  include/hw/virtio/virtio.h |  2 ++
>  3 files changed, 28 insertions(+), 3 deletions(-)
>
> diff --git a/hw/virtio/virtio-pci.c b/hw/virtio/virtio-pci.c
> index cb6940fc0e..f3e0a08f53 100644
> --- a/hw/virtio/virtio-pci.c
> +++ b/hw/virtio/virtio-pci.c
> @@ -384,7 +384,7 @@ static void virtio_ioport_write(void *opaque, uint32_t 
> addr, uint32_t val)
>  {
>      VirtIOPCIProxy *proxy = opaque;
>      VirtIODevice *vdev = virtio_bus_get_device(&proxy->bus);
> -    uint16_t vector;
> +    uint16_t vector, vq_idx;
>      hwaddr pa;
>
>      switch (addr) {
> @@ -408,8 +408,13 @@ static void virtio_ioport_write(void *opaque, uint32_t 
> addr, uint32_t val)
>              vdev->queue_sel = val;
>          break;
>      case VIRTIO_PCI_QUEUE_NOTIFY:
> -        if (val < VIRTIO_QUEUE_MAX) {
> -            virtio_queue_notify(vdev, val);
> +        vq_idx = val;
> +        if (vq_idx < VIRTIO_QUEUE_MAX && virtio_queue_get_num(vdev, vq_idx)) 
> {
> +            if (virtio_vdev_has_feature(vdev, VIRTIO_F_NOTIFICATION_DATA)) {
> +                virtio_queue_set_shadow_avail_idx(virtio_get_queue(vdev, 
> vq_idx),
> +                                                  val >> 16);
> +            }
> +            virtio_queue_notify(vdev, vq_idx);
>          }
>          break;
>      case VIRTIO_PCI_STATUS:
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index d229755eae..463426ca92 100644
> --- a/hw/virtio/virtio.c
> +++ b/hw/virtio/virtio.c
> @@ -2255,6 +2255,24 @@ void virtio_queue_set_align(VirtIODevice *vdev, int n, 
> int align)
>      }
>  }
>
> +void virtio_queue_set_shadow_avail_idx(VirtQueue *vq, uint16_t 
> shadow_avail_idx)
> +{
> +    if (!vq->vring.desc) {
> +        return;
> +    }
> +
> +    /*
> +     * 16-bit data for packed VQs include 1-bit wrap counter and
> +     * 15-bit shadow_avail_idx.
> +     */
> +    if (virtio_vdev_has_feature(vq->vdev, VIRTIO_F_RING_PACKED)) {
> +        vq->shadow_avail_wrap_counter = (shadow_avail_idx >> 15) & 0x1;
> +        vq->shadow_avail_idx = shadow_avail_idx & 0x7FFF;
> +    } else {
> +        vq->shadow_avail_idx = shadow_avail_idx;
> +    }
> +}
> +
>  static void virtio_queue_notify_vq(VirtQueue *vq)
>  {
>      if (vq->vring.desc && vq->handle_output) {
> diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
> index c8f72850bc..cdd4f86b61 100644
> --- a/include/hw/virtio/virtio.h
> +++ b/include/hw/virtio/virtio.h
> @@ -306,6 +306,8 @@ int virtio_queue_ready(VirtQueue *vq);
>
>  int virtio_queue_empty(VirtQueue *vq);
>
> +void virtio_queue_set_shadow_avail_idx(VirtQueue *vq, uint16_t idx);
> +
>  /* Host binding interface.  */
>
>  uint32_t virtio_config_readb(VirtIODevice *vdev, uint32_t addr);
> --
> 2.39.3
>