Re: [PULL v4 29/83] virtio: introduce virtio_queue_enable()

[Stefan Hajnoczi]

On Mon, 7 Nov 2022 at 18:10, Michael S. Tsirkin <mst@redhat.com> wrote:
>
> From: Kangjie Xu <kangjie.xu@linux.alibaba.com>
>
> Introduce the interface queue_enable() in VirtioDeviceClass and the
> fucntion virtio_queue_enable() in virtio, it can be called when
> VIRTIO_PCI_COMMON_Q_ENABLE is written and related virtqueue can be
> started. It only supports the devices of virtio 1 or later. The
> not-supported devices can only start the virtqueue when DRIVER_OK.
>
> Signed-off-by: Kangjie Xu <kangjie.xu@linux.alibaba.com>
> Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> Acked-by: Jason Wang <jasowang@redhat.com>
> Message-Id: <20221017092558.111082-4-xuanzhuo@linux.alibaba.com>
> Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
>  include/hw/virtio/virtio.h |  2 ++
>  hw/virtio/virtio.c         | 14 ++++++++++++++
>  2 files changed, 16 insertions(+)
>
> diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
> index 74d76c1dbc..b00b3fcf31 100644
> --- a/include/hw/virtio/virtio.h
> +++ b/include/hw/virtio/virtio.h
> @@ -149,6 +149,7 @@ struct VirtioDeviceClass {
>      void (*reset)(VirtIODevice *vdev);
>      void (*set_status)(VirtIODevice *vdev, uint8_t val);
>      void (*queue_reset)(VirtIODevice *vdev, uint32_t queue_index);
> +    void (*queue_enable)(VirtIODevice *vdev, uint32_t queue_index);
>      /* For transitional devices, this is a bitmap of features
>       * that are only exposed on the legacy interface but not
>       * the modern one.
> @@ -288,6 +289,7 @@ int virtio_queue_set_host_notifier_mr(VirtIODevice *vdev, 
> int n,
>  int virtio_set_status(VirtIODevice *vdev, uint8_t val);
>  void virtio_reset(void *opaque);
>  void virtio_queue_reset(VirtIODevice *vdev, uint32_t queue_index);
> +void virtio_queue_enable(VirtIODevice *vdev, uint32_t queue_index);
>  void virtio_update_irq(VirtIODevice *vdev);
>  int virtio_set_features(VirtIODevice *vdev, uint64_t val);
>
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index cf5f9ca387..9683b2e158 100644
> --- a/hw/virtio/virtio.c
> +++ b/hw/virtio/virtio.c
> @@ -2495,6 +2495,20 @@ void virtio_queue_reset(VirtIODevice *vdev, uint32_t 
> queue_index)
>      __virtio_queue_reset(vdev, queue_index);
>  }
>
> +void virtio_queue_enable(VirtIODevice *vdev, uint32_t queue_index)
> +{
> +    VirtioDeviceClass *k = VIRTIO_DEVICE_GET_CLASS(vdev);
> +
> +    if (!virtio_vdev_has_feature(vdev, VIRTIO_F_VERSION_1)) {
> +        error_report("queue_enable is only suppported in devices of virtio "
> +                     "1.0 or later.");

Why is this triggering here? Maybe virtio_queue_enable() is called too
early. I have verified that the Linux guest driver sets VERSION_1. I
didn't check what SeaBIOS does.

$ build/qemu-system-x86_64 -M accel=kvm -m 1G -cpu host -blockdev
file,node-name=drive0,filename=test.img -device
virtio-blk-pci,drive=drive0
qemu: queue_enable is only suppported in devices of virtio 1.0 or later.

Stefan