From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg Kurz Subject: Re: [PATCH v5 6/8] virtio: add explicit big-endian support to memory accessors Date: Fri, 24 Apr 2015 09:56:26 +0200 Message-ID: <20150424095626.1871d188@bahia.local> References: <20150423152608.11795.4373.stgit@bahia.local> <20150423152712.11795.29245.stgit@bahia.local> <20150423212719.4b7f9507@thh440s> <20150424090421.123d6ff6.cornelia.huck@de.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20150424090421.123d6ff6.cornelia.huck-tA70FqPdS9bQT0dZR+AlfA@public.gmane.org> Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Cornelia Huck Cc: Thomas Huth , Rusty Russell , "Michael S. Tsirkin" , linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, kvm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, virtualization-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org List-Id: linux-api@vger.kernel.org On Fri, 24 Apr 2015 09:04:21 +0200 Cornelia Huck wrote: > On Thu, 23 Apr 2015 21:27:19 +0200 > Thomas Huth wrote: > Thomas's e-mail did not make it to my mailbox... weird. :-\ > > On Thu, 23 Apr 2015 17:29:06 +0200 > > Greg Kurz 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 > > > --- > > > > > > 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 :) > -- > To unsubscribe from this list: send the line "unsubscribe kvm" in > the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >