On Fri, 24 Apr 2015 09:04:21 +0200
Cornelia Huck <cornelia.huck@xxxxxxxxxx> wrote:
> On Thu, 23 Apr 2015 21:27:19 +0200
> Thomas Huth <thuth@xxxxxxxxxx> wrote:
>
Thomas's e-mail did not make it to my mailbox... weird. :-\
> > On Thu, 23 Apr 2015 17:29:06 +0200
> > Greg Kurz <gkurz@xxxxxxxxxxxxxxxxxx> wrote:
> >
> > > The current memory accessors logic is:
> > > - little endian if little_endian
> > > - native endian (i.e. no byteswap) if !little_endian
> > >
> > > If we want to fully support cross-endian vhost, we also need to be
> > > able to convert to big endian.
> > >
> > > Instead of changing the little_endian argument to some 3-value enum, this
> > > patch changes the logic to:
> > > - little endian if little_endian
> > > - big endian if !little_endian
> > >
> > > The native endian case is handled by all users with a trivial helper. This
> > > patch doesn't change any functionality, nor it does add overhead.
> > >
> > > Signed-off-by: Greg Kurz <gkurz@xxxxxxxxxxxxxxxxxx>
> > > ---
> > >
> > > Changes since v4:
> > > - style fixes (I have chosen if ... else in most places to stay below
> > > 80 columns, with the notable exception of the vhost helper which gets
> > > shorten in a later patch)
> > >
> > > drivers/net/macvtap.c | 5 ++++-
> > > drivers/net/tun.c | 5 ++++-
> > > drivers/vhost/vhost.h | 2 +-
> > > include/linux/virtio_byteorder.h | 24 ++++++++++++++----------
> > > include/linux/virtio_config.h | 5 ++++-
> > > include/linux/vringh.h | 2 +-
> > > 6 files changed, 28 insertions(+), 15 deletions(-)
> > >
> > > diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
> > > index a2f2958..6cf6b3e 100644
> > > --- a/drivers/net/macvtap.c
> > > +++ b/drivers/net/macvtap.c
> > > @@ -51,7 +51,10 @@ struct macvtap_queue {
> > >
> > > static inline bool macvtap_is_little_endian(struct macvtap_queue *q)
> > > {
> > > - return q->flags & MACVTAP_VNET_LE;
> > > + if (q->flags & MACVTAP_VNET_LE)
> > > + return true;
> > > + else
> > > + return virtio_legacy_is_little_endian();
> >
> > simply:
> >
> > return (q->flags & MACVTAP_VNET_LE) ||
> > virtio_legacy_is_little_endian();
> >
> > ?
>
> ISTR that MST preferred the current notation, but I like either your
> way or ?: (with linebreak) even better.
>
MST did not like the initial notation I had used actually. FWIW I
like the simplicity of Thomas's suggestion... even better than ?:
which is:
some_LE_check() ? true : some_default_endianness()
> >
> > > }
> > >
> (...)
> > > diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
> > > index 6a49960..954c657 100644
> > > --- a/drivers/vhost/vhost.h
> > > +++ b/drivers/vhost/vhost.h
> > > @@ -175,7 +175,7 @@ static inline bool vhost_has_feature(struct vhost_virtqueue *vq, int bit)
> > >
> > > static inline bool vhost_is_little_endian(struct vhost_virtqueue *vq)
> > > {
> > > - return vhost_has_feature(vq, VIRTIO_F_VERSION_1);
> > > + return vhost_has_feature(vq, VIRTIO_F_VERSION_1) ? true : virtio_legacy_is_little_endian();
> > > }
> >
> > That line is way longer than 80 characters ... may I suggest to switch
> > at least here to:
> >
> > return vhost_has_feature(vq, VIRTIO_F_VERSION_1) ||
> > virtio_legacy_is_little_endian();
>
> I think the line will collapse in a further patch anyway.
>
Yes, as mentionned in the changelog :)
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