Re: [Qemu-devel] [PATCH 0/8] Add virtio-mmio and use it in vexpress

[Alexander Graf]

On 08.07.2013, at 23:06, Anthony Liguori wrote:

> Alexander Graf <address@hidden> writes:
> 
>> On 08.07.2013, at 22:08, Anthony Liguori wrote:
>> 
>>> I think we're trying to fit a square peg into a round hole.
>>> 
>>> virtio-mmio is a virtio transport where each device has a dedicated set
>>> of system resources.
>>> 
>>> Alex, it sounds like you want virtio-mmio-bus which would be a single
>>> set of system resources that implemented a virtio bus on top of it.
>> 
>> Well, what I really want is a sysbus that behaves like PCI from a
>> usability point of view ;).
> 
> Which means you need to have (1) a discovery mechanism with a stable
> addressing mechanism

That's what dtb usually gives you.

> (2) a way to communicate this to the guest from the
> host.

Not if the host dictates everything. PCI is only complicated because it allows 
the guest control. If we don't we can have a push-only interface.

But I'm not sure we should hold back this patch series based on this. I can try 
to come up with a bus that can automatically place memory regions and IRQs. 
Then I can add a virtio-mmio-awesomebus type and show you what I mean ;)

For the time being, we can live with a few statically allocated virtio 
transports I think. As long as we don't promise the user that they're still 
going to be there in the next version of QEMU.


Alex