On Tuesday 22 April 2008 17:13:01 Anthony Liguori wrote: > Hollis Blanchard wrote: > > On Tuesday 22 April 2008 16:05:38 Rusty Russell wrote: > > > >> On Wednesday 23 April 2008 06:29:14 Hollis Blanchard wrote: > >> > >>> On Tuesday 22 April 2008 09:31:35 Rusty Russell wrote: > >>> > >>>> We may still regret not doing *everything* little-endian, but this > >>>> doesn't make it worse. > >>>> > >>> Hmm, why *don't* we just do everything LE, including the ring? > >>> > >> Mainly because when requirements are in doubt, simplicity wins, I think. > >> > > > > Well, I think the definition of simplicity is up for debate in this > > case... "LE everywhere" is much simpler than "it depends", IMHO. > > > > You couldn't use the vringfd direct ring mapping optimization in KVM for > PPC without teaching the kernel to access a vring in LE format. I'm > pretty sure the later would get rejected on LKML anyway for vringfd as a > generic mechanism. (Since the IA64 guys have already implemented BE guests on LE hosts, they should be aware of this discussion too, which is why I've CCed them.) After a short but torturous whiteboard session, followed by a much longer but less painful discussion, I'm fine with the virtio device config space being BE for PowerPC and LE for x86. In the future, we can use a feature bit to indicate that PCI config space contains an explicit endianness flag. (This will be set to BE or LE, *not* to "opposite of normal", because "normal" is also too vague.) -- Hollis Blanchard IBM Linux Technology Center _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/virtualization
