Re: [Alacrityvm-devel] [GIT PULL] AlacrityVM guest drivers for 2.6.33

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On 12/23/2009 01:54 PM, Ira W. Snyder wrote:
On Wed, Dec 23, 2009 at 09:09:21AM -0600, Anthony Liguori wrote:

I didn't know you were interested in this as well. See my later reply to
Kyle for a lot of code that I've written with this in mind.


BTW, in the future, please CC me or CC virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxxx Or certainly kvm@vger. I never looked at the virtio-over-pci patchset although I've heard it referenced before.

But both virtio-lguest and virtio-s390 use in-band enumeration and
discovery since they do not have support for PCI on either platform.


I'm interested in the same thing, just over PCI. The only PCI agent
systems I've used are not capable of manipulating the PCI configuration
space in such a way that virtio-pci is usable on them.

virtio-pci is the wrong place to start if you want to use a PCI *device* as the virtio bus. virtio-pci is meant to use the PCI bus as the virtio bus. That's a very important requirement for us because it maintains the relationship of each device looking like a normal PCI device.

This means
creating your own enumeration mechanism. Which sucks.

I don't think it sucks. The idea is that we don't want to unnecessarily reinvent things.

Of course, the key feature of virtio is that it makes it possible for you to create your own enumeration mechanism if you're so inclined.

See my virtio-phys
code (http://www.mmarray.org/~iws/virtio-phys/) for an example of how I
did it. It was modeled on lguest. Help is appreciated.

If it were me, I'd take a much different approach. I would use a very simple device with a single transmit and receive queue. I'd create a standard header, and the implement a command protocol on top of it. You'll be able to support zero copy I/O (although you'll have a fixed number of outstanding requests). You would need a single large ring.

But then again, I have no idea what your requirements are. You could probably get far treating the thing as a network device and just doing ATAoE or something like that.

Regards,

Anthony Liguori

Ira

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