Re: [kvm-devel] [RFC PATCH] virtio: change config to guest endian.

[Hollis B. <ho...@us...>]

On Tuesday 22 April 2008 06:22:48 Avi Kivity wrote:
> Rusty Russell wrote:
> > [Christian, Hollis, how much is this ABI breakage going to hurt you?]
> >
> > A recent proposed feature addition to the virtio block driver revealed
> > some flaws in the API, in particular how easy it is to break big
> > endian machines.
> >
> > The virtio config space was originally chosen to be little-endian,
> > because we thought the config might be part of the PCI config space
> > for virtio_pci.  It's actually a separate mmio region, so that
> > argument holds little water; as only x86 is currently using the virtio
> > mechanism, we can change this (but must do so now, before the
> > impending s390 and ppc merges).
> 
> This will probably annoy Hollis which has guests that can go both ways.

Rusty and I have discussed it. Ultimately, this just takes us from a 
cross-architecture endianness definition to a per-architecture definition. 
Anyways, we've already fallen into this situation with the virtio ring data 
itself, so we're really saying "same endianness as the ring".

-- 
Hollis Blanchard
IBM Linux Technology Center