On Wed, Jun 18, 2014 at 02:35:21PM +0200, Greg Kurz wrote: > On Wed, 18 Jun 2014 18:38:14 +0800 > Stefan Hajnoczi <stefa...@gmail.com> wrote: > > > On Tue, Jun 17, 2014 at 09:40:19AM +0200, Alexander Graf wrote: > > > > > > On 17.06.14 09:36, Stefan Hajnoczi wrote: > > > >On Fri, Jun 13, 2014 at 01:18:00PM +0200, Greg Kurz wrote: > > > >>This version merges the changes requested during the v7 review, remarks > > > >>from > > > >>ppc64 dump support review (yes, we talked about virtio there) and the > > > >>work on > > > >>virtio subsections migration. Also two new patches have been added: > > > >>- patch #1 is a preliminary fix for virtio-serial posted by Alexander > > > >>Graf > > > >>- patch #9 prepares the work on the virtio_is_big_endian() helper > > > >> > > > >>The most significant changes are: > > > >>- introduction of a new CPU method for virtio > > > >>- endianness is taken from CPU that resets the device > > > >>- fastpath virtio memory accessors for fixed endian targets > > > >>- VMState based virtio subsections (compatibility friendly) > > > >I'm surprised it's not enough for the virtio device to have an > > > >endianness field (big/little). It seems these patches make endianness > > > >depend on the CPUState through which the device is being accessed. > > > > > > > >Can you explain why it's necessary to check the CPUState? > > > > > > They only check CPUState at the point in time of reset, as that's the only > > > case where we can derive the implicit endian configuration from :). > > > > What bothers me is that real hardware can't do this. 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. > > > > Stefan > > Hi Stefan, > > Previous versions of this patch set had such comments: > > "virtio data structures are defined as "target endian", which assumes > that's a fixed value. In fact, that actually means it's platform-specific. > The OASIS virtio 1.0 spec will fix this, by making all little endian. > > We need to support both implementations and we want to share as much code > as possible." > > but these lines got lost between v6 and v7... my bad... :-\
Thanks! I just wasn't mentally prepared when looking through the patch series, the comment puts it into context. Stefan
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