Re: [GIT PULL] AlacrityVM guest drivers for 2.6.33

From: Anthony Liguori
Date: Wed Dec 23 2009 - 10:09:34 EST

On 12/23/2009 12:15 AM, Kyle Moffett wrote:
This is actually something that is of particular interest to me. I
have a few prototype boards right now with programmable PCI-E
host/device links on them; one of my long-term plans is to finagle
vbus into providing multiple "virtual" devices across that single
PCI-E interface.

Specifically, I want to be able to provide virtual NIC(s), serial
ports and serial consoles, virtual block storage, and possibly other
kinds of interfaces. My big problem with existing virtio right now
(although I would be happy to be proven wrong) is that it seems to
need some sort of out-of-band communication channel for setting up
devices, not to mention it seems to need one PCI device per virtual

We've been thinking about doing a virtio-over-IP mechanism such that you could remote the entire virtio bus to a separate physical machine. virtio-over-IB is probably more interesting since you can make use of RDMA. virtio-over-PCI-e would work just as well.

virtio is a layered architecture. Device enumeration/discovery sits at a lower level than the actual device ABIs. The device ABIs are implemented on top of a bulk data transfer API. The reason for this layering is so that we can reuse PCI as an enumeration/discovery mechanism. This tremendenously simplifies porting drivers to other OSes and let's us use PCI hotplug automatically. We get integration into all the fancy userspace hotplug support for free.

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


Anthony Liguori
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