From mboxrd@z Thu Jan 1 00:00:00 1970 From: Cornelia Huck Subject: Re: [PATCH v5 6/8] virtio: add explicit big-endian support to memory accessors Date: Fri, 24 Apr 2015 09:04:21 +0200 Message-ID: <20150424090421.123d6ff6.cornelia.huck@de.ibm.com> References: <20150423152608.11795.4373.stgit@bahia.local> <20150423152712.11795.29245.stgit@bahia.local> <20150423212719.4b7f9507@thh440s> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20150423212719.4b7f9507@thh440s> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Thomas Huth Cc: kvm@vger.kernel.org, "Michael S. Tsirkin" , linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org List-Id: linux-api@vger.kernel.org On Thu, 23 Apr 2015 21:27:19 +0200 Thomas Huth wrote: > 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. > > > } > > (...) > > 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.