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

[Xuan Zhuo]

On Wed, 9 Nov 2022 14:55:03 +0800, Jason Wang <jasowang@redhat.com> wrote:
>
> 在 2022/11/9 14:51, Michael S. Tsirkin 写道:
> > On Wed, Nov 09, 2022 at 11:31:23AM +0800, Jason Wang wrote:
> >> On Wed, Nov 9, 2022 at 3:43 AM Stefan Hajnoczi <stefanha@gmail.com> wrote:
> >>> 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.
> >> Looks like a bug, we should check device features here at least and it
> >> should be guest errors instead of error_report() here.
> >>
> >> Thanks
> > But it's weird, queue enable is written before guest features?
> > How come?
>
>
> Or queue_enable is written when the driver doesn't negotiate VERSION_1?

Is this a bug?

Or is it allowed in some cases?

I feel weird too.

Thanks.

>
> Thanks
>
>
> >
> >>> $ 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
> >>>
>