On 7/22/21 5:22 AM, Jason Wang wrote:
>
> 在 2021/7/21 下午4:59, Jonah Palmer 写道:
>>
>>
>> On 7/13/21 10:37 PM, Jason Wang wrote:
>>>
>>> 在 2021/7/12 下午6:35, Jonah Palmer 写道:
>>>> From: Laurent Vivier <lvivier@redhat.com>
>>>>
>>>> This new command shows internal status of a VirtQueue.
>>>> (vrings and indexes).
>>>>
>>>> Signed-off-by: Laurent Vivier <lvivier@redhat.com>
>>>> Signed-off-by: Jonah Palmer <jonah.palmer@oracle.com>
>>>> ---
>>>>   hw/virtio/virtio-stub.c |   6 +++
>>>>   hw/virtio/virtio.c      |  37 ++++++++++++++++++
>>>>   qapi/virtio.json        | 102 
>>>> ++++++++++++++++++++++++++++++++++++++++++++++++
>>>>   3 files changed, 145 insertions(+)
>>>>
>>>>   [Jonah: Added 'device-type' field to VirtQueueStatus and
>>>>   qmp command x-debug-virtio-queue-status.]
>>>>
>>>> diff --git a/hw/virtio/virtio-stub.c b/hw/virtio/virtio-stub.c
>>>> index ddb592f..3c1bf17 100644
>>>> --- a/hw/virtio/virtio-stub.c
>>>> +++ b/hw/virtio/virtio-stub.c
>>>> @@ -17,3 +17,9 @@ VirtioStatus *qmp_x_debug_virtio_status(const 
>>>> char* path, Error **errp)
>>>>   {
>>>>       return qmp_virtio_unsupported(errp);
>>>>   }
>>>> +
>>>> +VirtQueueStatus *qmp_x_debug_virtio_queue_status(const char *path,
>>>> +                                                 uint16_t queue, 
>>>> Error **errp)
>>>> +{
>>>> +    return qmp_virtio_unsupported(errp);
>>>> +}
>>>> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
>>>> index 81a0ee8..ccd4371 100644
>>>> --- a/hw/virtio/virtio.c
>>>> +++ b/hw/virtio/virtio.c
>>>> @@ -3935,6 +3935,43 @@ 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->device_type = qapi_enum_parse(&VirtioType_lookup, 
>>>> vdev->name,
>>>> + VIRTIO_TYPE_UNKNOWN, NULL);
>>>> +    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;
>>>
>>>
>>> As mentioned in previous versions. We need add vhost support 
>>> otherwise the value here is wrong.
>> Got it. I'll add a case to determine if vhost is active for a given 
>> device.
>> So, in the case that vhost is active, should I just not print out the 
>> value or would I substitute it with
>> another value (whatever that might be)?
>
>
> You can query the vhost for those index.
>
> (vhost_get_vring_base())
>
>
>>   Same question for shadow_avail_idx below as well.
>
>
> It's an implementation specific. I think we can simply not show it if 
> vhost is enabled.
>
> Thanks

Ah I see, thank you!

So, it appears to me that it's not very easy to get the struct vhost_dev 
pointer from struct VirtIODevice to indicate whether or not vhost is 
active, e.g. there's no virtio class-independent way to get struct 
vhost_dev.

I was thinking of adding an op/callback function to struct 
VirtioDeviceClass, e.g. bool has_vhost(VirtIODevice *vdev), and 
implement it for each virtio class (net, scsi, blk, etc.).

For example, for virtio-net, maybe it'd be something like:

bool has_vhost(VirtIODevice *vdev) {
   VirtIONet *n = VIRTIO_NET(vdev);
   NetClientState *nc = qemu_get_queue(n->nic);
   return nc->peer ? get_vhost_net(nc->peer) : false;
}

Also, for getting the last_avail_idx, I was also thinking of adding 
another op/callback to struct VirtioDeviceClass, e.g. unsigned int 
get_last_avail_idx(VirtIODevice *vdev, unsigned int vq_idx) that finds 
if vhost is active or not and either gets last_avail_idx from virtio 
directly or through vhost (e.g. 
vhost_dev->vhost_ops->vhost_get_vring_base()).

I wanted to run this by you and get your opinion on this before I 
started implementing it in code. Let me know what you think about this.


Jonah

>
>
>>
>> Jonah
>>>
>>>
>>>> +    status->shadow_avail_idx = vdev->vq[queue].shadow_avail_idx;
>>>
>>>
>>> The shadow index is something that is implementation specific e.g in 
>>> the case of vhost it's kind of meaningless.
>>>
>>> Thanks
>>>
>>>
>>>> +    status->used_idx = vdev->vq[queue].used_idx;
>>>> +    status->signalled_used = vdev->vq[queue].signalled_used;
>>>> +    status->signalled_used_valid = 
>>>> vdev->vq[queue].signalled_used_valid;
>>>> +
>>>> +    return status;
>>>> +}
>>>> +
>>>>   #define CONVERT_FEATURES(type, map)                \
>>>>       ({                                           \
>>>>           type *list = NULL;                         \
>>>> diff --git a/qapi/virtio.json b/qapi/virtio.json
>>>> index 78873cd..7007e0c 100644
>>>> --- a/qapi/virtio.json
>>>> +++ b/qapi/virtio.json
>>>> @@ -406,3 +406,105 @@
>>>>     'data': { 'path': 'str' },
>>>>     'returns': 'VirtioStatus'
>>>>   }
>>>> +
>>>> +##
>>>> +# @VirtQueueStatus:
>>>> +#
>>>> +# Status of a VirtQueue
>>>> +#
>>>> +# @device-type: VirtIO device type
>>>> +#
>>>> +# @queue-index: VirtQueue queue_index
>>>> +#
>>>> +# @inuse: VirtQueue inuse
>>>> +#
>>>> +# @vring-num: VirtQueue vring.num
>>>> +#
>>>> +# @vring-num-default: VirtQueue vring.num_default
>>>> +#
>>>> +# @vring-align: VirtQueue vring.align
>>>> +#
>>>> +# @vring-desc: VirtQueue vring.desc
>>>> +#
>>>> +# @vring-avail: VirtQueue vring.avail
>>>> +#
>>>> +# @vring-used: VirtQueue vring.used
>>>> +#
>>>> +# @last-avail-idx: VirtQueue last_avail_idx
>>>> +#
>>>> +# @shadow-avail-idx: VirtQueue shadow_avail_idx
>>>> +#
>>>> +# @used-idx: VirtQueue used_idx
>>>> +#
>>>> +# @signalled-used: VirtQueue signalled_used
>>>> +#
>>>> +# @signalled-used-valid: VirtQueue signalled_used_valid
>>>> +#
>>>> +# Since: 6.1
>>>> +#
>>>> +##
>>>> +
>>>> +{ 'struct': 'VirtQueueStatus',
>>>> +  'data': {
>>>> +    'device-type': 'VirtioType',
>>>> +    'queue-index': 'uint16',
>>>> +    'inuse': 'uint32',
>>>> +    'vring-num': 'int',
>>>> +    'vring-num-default': 'int',
>>>> +    'vring-align': 'int',
>>>> +    'vring-desc': 'uint64',
>>>> +    'vring-avail': 'uint64',
>>>> +    'vring-used': 'uint64',
>>>> +    'last-avail-idx': 'uint16',
>>>> +    'shadow-avail-idx': 'uint16',
>>>> +    'used-idx': 'uint16',
>>>> +    'signalled-used': 'uint16',
>>>> +    'signalled-used-valid': 'uint16'
>>>> +  }
>>>> +}
>>>> +
>>>> +##
>>>> +# @x-debug-virtio-queue-status:
>>>> +#
>>>> +# Return the status of a given VirtQueue
>>>> +#
>>>> +# @path: QOBject path of the VirtIODevice
>>>> +#
>>>> +# @queue: queue number to examine
>>>> +#
>>>> +# Returns: Status of the VirtQueue
>>>> +#
>>>> +# Since: 6.1
>>>> +#
>>>> +# Example:
>>>> +#
>>>> +# -> { "execute": "x-debug-virtio-queue-status",
>>>> +#      "arguments": {
>>>> +#          "path": 
>>>> "/machine/peripheral-anon/device[3]/virtio-backend",
>>>> +#          "queue": 0
>>>> +#      }
>>>> +#   }
>>>> +# <- { "return": {
>>>> +#      "signalled-used": 373,
>>>> +#      "inuse": 0,
>>>> +#      "vring-align": 4096,
>>>> +#      "vring-desc": 864411648,
>>>> +#      "signalled-used-valid": 0,
>>>> +#      "vring-num-default": 256,
>>>> +#      "vring-avail": 864415744,
>>>> +#      "queue-index": 0,
>>>> +#      "last-avail-idx": 373,
>>>> +#      "vring-used": 864416320,
>>>> +#      "used-idx": 373,
>>>> +#      "device-type": "virtio-net",
>>>> +#      "shadow-avail-idx": 619,
>>>> +#      "vring-num": 256
>>>> +#      }
>>>> +#    }
>>>> +#
>>>> +##
>>>> +
>>>> +{ 'command': 'x-debug-virtio-queue-status',
>>>> +  'data': { 'path': 'str', 'queue': 'uint16' },
>>>> +  'returns': 'VirtQueueStatus'
>>>> +}
>>>
>