Re: virtio-pci new configuration proposal
From: Rusty Russell
Date: Wed Nov 02 2011 - 23:52:09 EST
On Wed, 02 Nov 2011 20:49:27 +0200, Sasha Levin <levinsasha928@xxxxxxxxx> wrote:
> This is a proposal for a new layout of the virtio-pci config space.
>
> We will separate the current configuration into two: A virtio-pci common
> configuration and a device specific configuration. This allows more flexibility
> with adding features and makes usage easier, specifically in cases like the
> ones in virtio-net where device specific configurations depend on device
> specific features.
Thanks for this Sasha. Several general comments:
1) How to we distinguish the two layouts? In theory, we need to do this
forever. In practice we can deprecate the old layout in several
years' time.
2) I don't think we want to turn the device-specific config into a
linked list. We haven't needed variable-length config (yet!), and
it's (slightly) more complex. That's also the part of the spec which
is shared with non-PCI virtio implementations.
3) If we're changing the queue layout, it's a chance to fix a
longstanding bug: let the guest notify the host of preferred
queue size and alignment.
Cheers,
Rusty.
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