Re: [virtio-comment] Re: [virtio] [OASIS Issue Tracker] Created: (VIRTIO-9) Change config space, ring and headers to always be little endian

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Aug 21, 2013 at 04:37:35PM +0930, Rusty Russell wrote:
> Stefan Hajnoczi <stefanha@redhat.com> writes:
> > On Mon, Aug 19, 2013 at 05:57:49PM +0930, Rusty Russell wrote:
> >> OASIS Issues Tracker <workgroup_mailer@lists.oasis-open.org> writes:
> >
> > What is the transition plan for existing virtio implementations?
> >
> > On x86 it's not an issue since guest endian == little-endian.  Not sure
> > about others.
> 
> Indeed!  I didn't cover that at all.  We're supposed to produce a
> separate transition guide: it's a deliverable after the main spec
> itself.

For now, I'm working on making spec describe both legacy layout
and the new spec.
I think it will be easier to do it like this, and if necessary,
separate this out later.

> For PCI, we're looking at using PCI capabilities to describe the device:
> we want more feature bits and other changes anyway.  The new endianness
> (and any other changes) would be tied to that new layout.
> 
> For MMIO and CCW, there's no equivalent transition point proposed.  A
> feature bit?  Some other boutique marker?  See ongoing discussion...
> 
> >>  	struct virtio_blk_req {
> >> -		u32 type;
> >> -		u32 ioprio;
> >> -		u64 sector;
> >> +		le32 type;
> >> +		le32 ioprio;
> >> +		le64 sector;
> >>  		char data[][512];
> >> -		u8 status;
> >> +		le8 status;
> >
> > spurious change, there is no le8.
> 
> Oops, thanks.  Overzealous search/replace.
> 
> Cheers,
> Rusty.
> 
> 
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