On Wed, Jun 18, 2014 at 04:28:04PM +0200, Greg Kurz wrote: > On Wed, 18 Jun 2014 16:42:04 +0300 > "Michael S. Tsirkin" <m...@redhat.com> wrote: > > On Wed, Jun 18, 2014 at 01:53:15PM +0100, Peter Maydell wrote: > > > On 18 June 2014 11:38, Stefan Hajnoczi <stefa...@gmail.com> wrote: > > > > What bothers me is that real hardware can't do this. > > > > > > Real hardware doesn't have "endianness matches guest CPU endianness" > > > semantics, which is what the virtio spec mandates... > > > > So it was buggy. We never thought anyone would do a cross endian CPU :(. > > We are fixing it in 1.0. > > > > virtio isn't the only victim... we also have vga. The problem can pop up > anywhere you rely on TARGET_WORDS_BIGENDIAN. > > > > > Given that VIRTIO > > > > 1.0 is always little-endian I guess this is just a temporary hack for > > > > ppc little-endian. Would be nice to add a comment so it's clear why > > > > this approach is being taken instead of a cleaner solution. > > > > > > Also for ARM big-endian, and indeed for any CPU with runtime > > > configurable endianness that wants to use the kernel virtio > > > drivers that exist in the real world rather than the theoretical > > > future ones that might some day be written for the 1.0 virtio > > > spec... > > > > > > thanks > > > -- PMM > > > > That's not a theoretical future. > > Spec will almost certainly be frozen two weeks from now. > > So it is almost certain that drivers will be there in 3.17. > > > > I don't want argue on the dates but I doubt that all legacy users > will switch to 1.0 as soon as it shows up... a transition period > may be needed. > > > Existing distros can then simply backport the > > drivers - same as they would with any other new hardware. > > > > Are you saying that upstream QEMU should not to support the > transition between legacy and 1.0 at all ? > > Cheers.
Not at all. I wouldn't invest the time in implementing this feature myself: I would just wait a bit and then work on backporting drivers instead. But you did and the patches are surprisingly clean. So I don't see a reason to keep them out of tree. > -- > Gregory Kurz kurzg...@fr.ibm.com > gk...@linux.vnet.ibm.com > Software Engineer @ IBM/Meiosys http://www.ibm.com > Tel +33 (0)562 165 496 > > "Anarchy is about taking complete responsibility for yourself." > Alan Moore.
