Re: [Qemu-devel] [RFC PATCH v6 0/6] Virtio refactoring.

[Anthony Liguori <aliguori@us.ibm.com>]

"Michael S. Tsirkin" <mst@redhat.com> writes:

> On Tue, Dec 18, 2012 at 12:30:20PM +0100, KONRAD Frédéric wrote:
>> On 18/12/2012 12:01, Michael S. Tsirkin wrote:
>> >On Tue, Dec 18, 2012 at 10:33:37AM +0000, Peter Maydell wrote:
>> >>On 17 December 2012 15:45, Michael S. Tsirkin <mst@redhat.com> wrote:
>> >>>Is the point to allow virtio-mmio?  Why can't virtio-mmio be just
>> >>>another bus, like a pci bus, and another binding, like the virtio-pci
>> >>>binding?
>> >>(a) the current code is really not very nice because it's not
>> >>actually a proper set of QOM/qdev devices
>> >>(b) unlike PCI, you can't create sysbus devices on the
>> >>command line, because they don't correspond to a user
>> >>pluggable bit of hardware. We don't want users to have to know
>> >>an address and IRQ number for each virtio-mmio device (especially
>> >>since these are board specific); instead the board can create
>> >>and wire up transport devices wherever is suitable, and the
>> >>user just creates the backend (which is plugged into the virtio bus).
>> >>
>> >>-- PMM
>> >This is what I am saying: create your own bus and put
>> >your devices there. Allocate resources when you init
>> >a device.
>> >
>> >Instead you seem to want to expose a virtio device as two devices to
>> >user - if true this is not reasonable.
>> >
>> The modifications will be transparent to the user, as we will keep
>> virtio-x-pci devices.
>
> So there are three ways to add virtio pci devices now.
> Legacy -device virtio-net-pci, legacy legacy -net nic.model=virtio
> and the new one with two devices.
> If yes it's not transparent, it's user visible.
> Or did I misunderstand?
>
> Look we can have a virtio network device on a PCI bus.
> A very similar device can be created on XXX bus, and
> we can and do share a lot of code.
> This makes it two devices? Why not 4?
> One for TX one for RX one for control one for PCI.
> I hope I'm not giving anyone ideas ...

Devices != things users need to worry about.

The documented way to create network devices is completely different
than any possible syntax you can conjure up with -device.

Really, -device is not something users should have to deal with--ever.
It's a low level API, not a UI.

Regards,

Anthony Liguori

>
> -- 
> MST