Re: [PATCH v6 0/6] hmp, qmp: Add some commands to introspect virtio devices

[Jonah Palmer <jonah.palmer@oracle.com>]

On 7/22/21 5:16 AM, Jason Wang wrote:
>
> 在 2021/7/21 下午4:53, Jonah Palmer 写道:
>>
>> Hi Jason. My apologies for the delayed response, several work-related 
>> things came up recently, but they're slowing down now so I'm turning 
>> my attention these patches to get taken care of.
>>
>> A few questions and comments below (and in other following patches):
>>
>>
>> On 7/13/21 10:42 PM, Jason Wang wrote:
>>>
>>> 在 2021/7/12 下午6:35, Jonah Palmer 写道:
>>>>          Dump the information of the head element of the third 
>>>> queue of virtio-scsi:
>>>>
>>>>          (qemu) virtio queue-element 
>>>> /machine/peripheral-anon/device[3]/virtio-backend 3
>>>>          index: 122
>>>>          ndescs: 3
>>>>          descs: addr 0x7302d000 len 4096 (write), addr 0x3c951763 
>>>> len 108 (write, next),
>>>>                 addr 0x3c951728 len 51 (next)
>>>
>>>
>>> I think it would be nice if we can show driver area and device area 
>>> as well here.
>> Sure thing. And I apologize if it's obvious (I'm relatively new to 
>> virtio), but how can I expose the driver area?
>
>
> So the spec defines three parts: the device area, the driver area, and 
> the descriptor area. And they are all located in the guest memory.
>
>
>> I understand that virtio devices are part of the Qemu process, but I 
>> also thought that virtio drivers are in the
>> guest's kernel, which I don't believe I can see into from Qemu (or, 
>> at least, it's not obvious to me).
>
>
> It works like how you access the descriptor ring (descriptor area).
>
> Thanks

Oh, I see now! I didn't realize the device area is essentially the used 
ring and the driver area is the avail ring (at least for the split 
virtqueue model). I see this in the virtio spec now.


Thank you!

>
>
>>
>> Jonah
>>>
>>> Thanks
>>>
>