Re: [Qemu-devel] Virtio-pci issue

[Stefan Hajnoczi]

On Thu, May 10, 2012 at 12:24 PM, Evgeny Voevodin
<address@hidden> wrote:
> Hi, guys!
>
> While trying to refactor virtio-pci as continuation of my RFC
> virtio-mmio patch series:
> http://lists.gnu.org/archive/html/qemu-devel/2012-04/msg03665.html
> I've faced a problem.
>
> I try to create virtio-pci-transport device to which virtio-blk,net,etc
> could be connected. Any board could create as many transport devices as
> it wants and then any actual back-end could be connected to that
> transport through a provided virtio-pci.x bus. virtio-pci-transport is
> derived from TYPE_PCI_DEVICE.
> The problem is that if I create transport devices and wish to connect
> back-ends to them, each back-end would set its properties to the class,
> not to the object.
> For example, vendor_id property is different for blk and net, but since
> they are both have same class PCIDeviceClass, they share that property.
>
> How to deal with this?

I think you are asking how a virtio-pci adapter can have device_id
value that depends on its VirtioDevice (not known at compile-time and
different between virtio-pci adapters).

You should be able to set the PCI device ID at runtime:

pci_config_set_device_id(pci_dev->config, device_id_from_virtio_device);

Take a look at hw/pci.c:pci_qdev_init().  The order of operations is important:

1. do_pci_register_device() sets up default values from PCIDeviceClass.
2. ->init(pci_dev) gets called, this is where your init code gets executed.

So it should be fine to set the PCI device ID at runtime from
VirtioPCIAdapter::init().

Stefan