Re: [RFC v3 4/6] qmp: add QMP command x-debug-virtio-queue-status

[Laurent Vivier <lvivier@redhat.com>]

On 08/05/2020 04:57, Jason Wang wrote:
> 
> On 2020/5/7 下午7:49, Laurent Vivier wrote:
>> This new command shows internal status of a VirtQueue.
>> (vrings and indexes).
>>
>> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
> 
> 
> It looks to me that packed virtqueue is not supported. It's better to
> add them in the future.

I agree, it's why the series still remains an "RFC".

...
>> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
>> index 59bf6ef651a6..57552bf05014 100644
>> --- a/hw/virtio/virtio.c
>> +++ b/hw/virtio/virtio.c
>> @@ -3877,6 +3877,41 @@ static VirtIODevice *virtio_device_find(const
>> char *path)
>>       return NULL;
>>   }
>>   +VirtQueueStatus *qmp_x_debug_virtio_queue_status(const char *path,
>> +                                                 uint16_t queue,
>> Error **errp)
>> +{
>> +    VirtIODevice *vdev;
>> +    VirtQueueStatus *status;
>> +
>> +    vdev = virtio_device_find(path);
>> +    if (vdev == NULL) {
>> +        error_setg(errp, "Path %s is not a VirtIO device", path);
>> +        return NULL;
>> +    }
>> +
>> +    if (queue >= VIRTIO_QUEUE_MAX || !virtio_queue_get_num(vdev,
>> queue)) {
>> +        error_setg(errp, "Invalid virtqueue number %d", queue);
>> +        return NULL;
>> +    }
>> +
>> +    status = g_new0(VirtQueueStatus, 1);
>> +    status->queue_index = vdev->vq[queue].queue_index;
>> +    status->inuse = vdev->vq[queue].inuse;
>> +    status->vring_num = vdev->vq[queue].vring.num;
>> +    status->vring_num_default = vdev->vq[queue].vring.num_default;
>> +    status->vring_align = vdev->vq[queue].vring.align;
>> +    status->vring_desc = vdev->vq[queue].vring.desc;
>> +    status->vring_avail = vdev->vq[queue].vring.avail;
>> +    status->vring_used = vdev->vq[queue].vring.used;
>> +    status->last_avail_idx = vdev->vq[queue].last_avail_idx;
> 
> 
> This might not be correct when vhost is used.
> 
> We may consider to sync last_avail_idx from vhost backends here?

Yes, but I don't know how to do that. Where can I find the information?

Thanks,
Laurent