Re: [Qemu-devel] [RFC PATCH v7 7/8] virtio-pci-blk : Switch to new API.

[Paolo Bonzini]

Il 12/12/2012 18:53, Andreas Färber ha scritto:
> Am 12.12.2012 15:25, schrieb Peter Maydell:
>> How will the PCI transport's PCI vendor/device/class IDs be
>> set (a) when a virtio-blk backend is created and separately
>> plugged into a virtio-pci transport (b) for the legacy
>> virtio-pci-blk? [ideally the answer to (b) should be "in the
>> same way as for (a)"]
> 
> The obvious answer would be that PCI properties need to be set on the
> PCI device, not an a VirtioDevice sitting on a virtio-bus.

Yes, but the question is *how*... if there will be no usable "-device
virtio-pci", the value of this refactoring becomes a bit lower...

Paolo

> I.e., with the proposed refactoring we'd have on the virtio-bus:
> 
> - VirtioDevice
>   + VirtioBlockDevice
>   + VirtioSCSIDevice - has-a scsi-bus
>   ...
> 
> In turn that means that every VirtioDevice to be exposed as PCI device
> to the guest needs it own PCIDevice exposing a private virtio-bus.
> 
> - PCIDevice
>   - VirtioPCIDevice - has-a virtio-bus
>     + virtio-blk-pci - has-a VirtioBlockDevice on its virtio-bus
>     + virtio-scsi-pci - has-a VirtioSCSIDevice on its virtio-bus
>     ...
> 
> This also happens to solve most of the migration compatibility pretty
> nicely because the wapping PCI devices would be used almost as before,
> some state may need to be forwarded to the VirtioDevice.
> 
> Finally supplying a public device_initialize() or so would be helpful
> for the latter since VMState cannot cross pointers IIRC. I'll look into
> that part since inlining the old qdev functions cripples my Tegra work.
> 
> Andreas
>