On Tue, 21 Jul 2020 18:44:56 +0200 Halil Pasic <pa...@linux.ibm.com> wrote:
> On Tue, 21 Jul 2020 09:40:10 -0400 > "Michael S. Tsirkin" <m...@redhat.com> wrote: > > > On Fri, Jul 17, 2020 at 11:29:28AM +0200, Marc Hartmayer wrote: > > > Since virtio existed even before it got standardized, the virtio > > > standard defines the following types of virtio devices: > > > > > > + legacy device (pre-virtio 1.0) > > > + non-legacy or VIRTIO 1.0 device > > > + transitional device (which can act both as legacy and non-legacy) > > > > > > Virtio 1.0 defines the fields of the virtqueues as little endian, > > > while legacy uses guest's native endian [1]. Currently libvhost-user > > > does not handle virtio endianness at all, i.e. it works only if the > > > native endianness matches with whatever is actually needed. That means > > > things break spectacularly on big-endian targets. Let us handle virtio > > > endianness for non-legacy as required by the virtio specification > > > [1]. We will fence non-legacy virtio devices with the upcoming patch. > > > > > > [1] > > > https://docs.oasis-open.org/virtio/virtio/v1.1/cs01/virtio-v1.1-cs01.html#x1-210003 > > > > > > Signed-off-by: Marc Hartmayer <mhart...@linux.ibm.com> > > > > > > --- > > > Note: As we don't support legacy virtio devices > > > > Who's "we" in this sentence? vhost user supports legacy generally ... > > In that sentence "we" is the library "libvhost-user". I would like > to avoid s390x being an oddball regarding this. Marc's previous > version made an attempt at correct endianness handling for legacy > and non-legacy. That spawned a discussion on how we don't want > legacy devices in this context. This series makes what seemed to be the > consensus reached in that discussion explicit: namely that libvhost-user > does not support legacy-virtio. Can someone please clarify what libvhost-user actually supports? virtio-fs is clearly non-legacy only, but in the changelog I also see a mention of scsi, and that one probably does support legacy? Can we make a distinction along the lines of: - if we are non-legacy, we support any endianness; - if we are legacy, we support little endian host/guest only?
