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

[Jason Wang]

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


> Jonah
> > Thanks