Re: [Qemu-devel] Questions on DeviceState and Virtio infrastructure

[Wei Liu <liuw@liuw.name>]

On Thu, Jun 30, 2011 at 4:31 PM, Alexander Graf <agraf@suse.de> wrote:
>
> On 29.06.2011, at 15:59, Wei Liu <liuw@liuw.name> wrote:
>
>> Hi, QEMU folks
>>
>> I know that I might have a bad title for this post, but I just don't
>> have better idea for the title.
>>
>> I'm developing virtio support for Xen pv guest, hoping to reuse the
>> virtio infrastructure in qemu, i.e. I'm planning to use qemu as
>> "virtio backend" for Xen pv. And qemu can be run as pv backend if
>> proper "machine" option is given.
>>
>> Maybe you've known that Xen pv guest utilizes Xenbus/Xenstore to
>> configure its paravirt devices. So I'm to configure virtio devices
>> with Xenbus/Xenstore as well. But in nowdays XenDevice in qemu does
>> not include a DeviceState. To my understanding, it is not connected to
>> qemu's internal buses or whatever (correct me if I'm wrong, I'm
>> relatively new to qemu).
>
> I'm not a huge fan of adding multiple different transports for virtio if we don't have to. IIRC Xen PV guests can do PCI device assignment, right? That means there is a PCI bus for them which we could reuse to run virtio-pci on.
>
> By then, you'd get all the virtio code for free and don't have to worry about maintaining yet another transport (which _is_ cumbersome)
>

Good point, I will check this.

I thought that Xen pv pci assignment is only used for pci passthrough.
But I will check the possibility to assign pv backend to guest.

Stefano, how would you say about this?

Wei.