Re: [Qemu-devel] Virtio-pci issue

[Evgeny Voevodin]

On 30.05.2012 11:56, Stefan Hajnoczi wrote:
> On Tue, May 29, 2012 at 4:48 AM, Evgeny Voevodin<address@hidden>  wrote:
> > On 28.05.2012 16:37, Stefan Hajnoczi wrote:
> > > On Thu, May 24, 2012 at 4:18 AM, Evgeny Voevodin<address@hidden>
> > >   wrote:
> > > > And also there is another problem that I've faced with. It is the ability
> > > > to
> > > > plug as many pci back-ends as board wants.
> > > > I mean that if for each back-end board should create a transport, then
> > > > user
> > > > have to know maximum number of transport instances
> > > > created by board. In the case of mmio transport I think that it's a
> > > > correct
> > > > behaviour, but for pci transport seems not.
> > > Not sure I understand the problem.  Can you rephrase it?
> > >
> > > Stefan
> > Ok, I'll try )
> > As I see, to connect a pci device to board it should be enough to specify
> > "-device ..." on command line.
> > And in the way virtio refactoring is moving, board should create transport
> > pci device to correspond each
> > back-end created by "-device ..." command.
> > So, if we create more back-ends with "-device" option then transports
> > created by board then there would be
> > back-ends that will not have corresponding transport device.
> > As result user should know maximum number of transport instances created by
> > board to not overrun it.
> > In the case of mmio I think it's normal, but not in the pci case. Am I
> > right?
> The only limit to PCI devices should be the number slots available.

Where number of slots is defined?

> For convenience we could continue to have virtio-blk-pci,
> virtio-net-pci, etc which actually just add a virtio-pci adapter and
> link it to a virtio device.
>
> Users that want full control can specify:
>    -device virtio-pci,id=virtio-pci.0
>    -device virtio-blk,transport=virtio-pci.0,...
>
> The board doesn't need to preallocate virtio-pci adapters.
>
> Stefan

You suggest transport device to be created by user...
In that case an interface would differ from mmio since in the case
of mmio a board should specify memory and irq mappings for transport device.

--
Kind regards,
Evgeny Voevodin,
Leading Software Engineer,
ASWG, Moscow R&D center, Samsung Electronics
e-mail: address@hidden