Re: [PATCH 0/3] virtio-mmio: handle BE guests on LE hosts

Michael S. Tsirkin
2013-10-14T08:59:31Z

On Mon, Oct 14, 2013 at 09:24:32AM +0100, Marc Zyngier wrote:
> Hi Michael,
>
> On 12/10/13 19:28, Michael S. Tsirkin wrote:
> > On Fri, Oct 11, 2013 at 03:36:08PM +0100, Marc Zyngier wrote:
> >> This small patch series adds just enough kernel infrastructure and
> >> fixes to allow a BE guest to use virtio-mmio on a LE host, provided
> >> that the host actually supports such madness.
> >>
> >> This has been tested on arm64, with some fixes to KVM and a set of
> >> changes to kvmtool, both which I am posting separately.
> >>
> >> A branch containing all the relevant changes is at:
> >> git://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git kvm-arm64/be-on-le-3.12-rc4
> >>
> >> Cc: Rusty Russell <rusty@rustcorp.com.au>
> >> Cc: Michael S. Tsirkin <mst@redhat.com>
> >> Cc: Pawel Moll <pawel.moll@arm.com>
> >
> > We are changing the spec to make everything LE instead of
> > the native endian.
> >
> > I think that'll fix the issue in a cleaner way.
>
> While I agree that it would solve the issue completely, it would also
> break all BE users. Is that really an option?

I proposed several ways to create "transitional devices"
which can detect and switch to old interface at run-time.

Pawel thinks that's not necessary so ...

> The whole goal of this series is to implement something that gracefully
> falls back to what we have today, not breaking anything in the process.
>
> Cheers,
>
> M.
> --
> Jazz is not dead. It just smells funny...