Re: [PATCH/RFC 7/9] Virtual network guest device driver

Anthony Liguori
2007-05-22T00:29:06Z

ron minnich wrote:
> OK, so what are we doing here? We're using a PCI abstraction, as a
> common abstraction,which is not common really, because we don't have a
> common abstraction? So we describe all these non-pci resources with a
> pci abstraction?
>

No. You're confusing PV device discovery with the actual paravirtual
transport. In a fully virtual environment like KVM, a PCI bus is
present. You need some way for the guest to detect that a PV device is
present. The most natural way to do this IMHO is to have an entry for
the PV device in the PCI bus. That will make a lot of existing code happy.

Once you've identified that the device exists, you're free to do
whatever you want with it.

Regards,

Anthony Liguori

> I don't get it at all. I really think the resource interface idea I
> mentioned, which is borrowed from Plan 9, makes a whole lot more
> sense. IBM Austin has already shown it in practice in the papers I
> referenced. It can work. A memory channel at the bottom, with a
> resource sharing protocol (9p) above it, and then you describe your
> resources via names and a simple file-directory model. Note that PCI
> sort of tries to do this tree model, but it's all binary, and, as
> noted, it's hardly universal.
>
> All of this is trivially exported over a network, so the use of shared
> memory channels in no way rules out network access. Plan 9 exports
> devices over the network routinely.
>
> If you're using a PCI abstraction, something has gone badly wrong I think.
>
> thanks
>
> ron
>
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