From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg Kurz Subject: Re: [PATCH v3 6/7] virtio: add explicit big-endian support to memory accessors Date: Tue, 21 Apr 2015 09:47:47 +0200 Message-ID: <20150421094747.06711f85__32970.3310308561$1429602504$gmane$org@bahia.local> References: <20150407120929.4213.8225.stgit@bahia.lab.toulouse-stg.fr.ibm.com> <20150407121533.4213.46434.stgit@bahia.lab.toulouse-stg.fr.ibm.com> <20150407175522-mutt-send-email-mst@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20150407175522-mutt-send-email-mst@redhat.com> 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: "Michael S. Tsirkin" Cc: linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org List-Id: virtualization@lists.linuxfoundation.org On Tue, 7 Apr 2015 17:56:25 +0200 "Michael S. Tsirkin" wrote: > On Tue, Apr 07, 2015 at 02:15:52PM +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 > > --- > > drivers/net/macvtap.c | 4 +++- > > drivers/net/tun.c | 4 +++- > > drivers/vhost/vhost.h | 4 +++- > > include/linux/virtio_byteorder.h | 24 ++++++++++++++---------- > > include/linux/virtio_config.h | 4 +++- > > include/linux/vringh.h | 4 +++- > > 6 files changed, 29 insertions(+), 15 deletions(-) > > > > diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c > > index a2f2958..0a03a66 100644 > > --- a/drivers/net/macvtap.c > > +++ b/drivers/net/macvtap.c > > @@ -51,7 +51,9 @@ 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; > > + return virtio_legacy_is_little_endian(); > > } > > > > static inline u16 macvtap16_to_cpu(struct macvtap_queue *q, __virtio16 val) > > Hmm I'm not sure how well this will work once you > actually make it dynamic. > Remains to be seen. > Oops I overlooked this mail... FWIW I could reboot/kexec from a ppc64 guest to ppc64le and back with the following QEMU: https://github.com/gkurz/qemu/commits/vhost/cross-endian > > diff --git a/drivers/net/tun.c b/drivers/net/tun.c > > index 3c3d6c0..053f9b6 100644 > > --- a/drivers/net/tun.c > > +++ b/drivers/net/tun.c > > @@ -208,7 +208,9 @@ struct tun_struct { > > > > static inline bool tun_is_little_endian(struct tun_struct *tun) > > { > > - return tun->flags & TUN_VNET_LE; > > + if (tun->flags & TUN_VNET_LE) > > + return true; > > + return virtio_legacy_is_little_endian(); > > } > > > > static inline u16 tun16_to_cpu(struct tun_struct *tun, __virtio16 val) > > diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h > > index 6a49960..4e9a186 100644 > > --- a/drivers/vhost/vhost.h > > +++ b/drivers/vhost/vhost.h > > @@ -175,7 +175,9 @@ 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); > > + if (vhost_has_feature(vq, VIRTIO_F_VERSION_1)) > > + return true; > > + return virtio_legacy_is_little_endian(); > > } > > > > /* Memory accessors */ > > diff --git a/include/linux/virtio_byteorder.h b/include/linux/virtio_byteorder.h > > index 51865d0..ce63a2c 100644 > > --- a/include/linux/virtio_byteorder.h > > +++ b/include/linux/virtio_byteorder.h > > @@ -3,17 +3,21 @@ > > #include > > #include > > > > -/* > > - * Low-level memory accessors for handling virtio in modern little endian and in > > - * compatibility native endian format. > > - */ > > +static inline bool virtio_legacy_is_little_endian(void) > > +{ > > +#ifdef __LITTLE_ENDIAN > > + return true; > > +#else > > + return false; > > +#endif > > +} > > > > static inline u16 __virtio16_to_cpu(bool little_endian, __virtio16 val) > > { > > if (little_endian) > > return le16_to_cpu((__force __le16)val); > > else > > - return (__force u16)val; > > + return be16_to_cpu((__force __be16)val); > > } > > > > static inline __virtio16 __cpu_to_virtio16(bool little_endian, u16 val) > > @@ -21,7 +25,7 @@ static inline __virtio16 __cpu_to_virtio16(bool little_endian, u16 val) > > if (little_endian) > > return (__force __virtio16)cpu_to_le16(val); > > else > > - return (__force __virtio16)val; > > + return (__force __virtio16)cpu_to_be16(val); > > } > > > > static inline u32 __virtio32_to_cpu(bool little_endian, __virtio32 val) > > @@ -29,7 +33,7 @@ static inline u32 __virtio32_to_cpu(bool little_endian, __virtio32 val) > > if (little_endian) > > return le32_to_cpu((__force __le32)val); > > else > > - return (__force u32)val; > > + return be32_to_cpu((__force __be32)val); > > } > > > > static inline __virtio32 __cpu_to_virtio32(bool little_endian, u32 val) > > @@ -37,7 +41,7 @@ static inline __virtio32 __cpu_to_virtio32(bool little_endian, u32 val) > > if (little_endian) > > return (__force __virtio32)cpu_to_le32(val); > > else > > - return (__force __virtio32)val; > > + return (__force __virtio32)cpu_to_be32(val); > > } > > > > static inline u64 __virtio64_to_cpu(bool little_endian, __virtio64 val) > > @@ -45,7 +49,7 @@ static inline u64 __virtio64_to_cpu(bool little_endian, __virtio64 val) > > if (little_endian) > > return le64_to_cpu((__force __le64)val); > > else > > - return (__force u64)val; > > + return be64_to_cpu((__force __be64)val); > > } > > > > static inline __virtio64 __cpu_to_virtio64(bool little_endian, u64 val) > > @@ -53,7 +57,7 @@ static inline __virtio64 __cpu_to_virtio64(bool little_endian, u64 val) > > if (little_endian) > > return (__force __virtio64)cpu_to_le64(val); > > else > > - return (__force __virtio64)val; > > + return (__force __virtio64)cpu_to_be64(val); > > } > > > > #endif /* _LINUX_VIRTIO_BYTEORDER */ > > diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h > > index bd1a582..36a6daa 100644 > > --- a/include/linux/virtio_config.h > > +++ b/include/linux/virtio_config.h > > @@ -207,7 +207,9 @@ int virtqueue_set_affinity(struct virtqueue *vq, int cpu) > > > > static inline bool virtio_is_little_endian(struct virtio_device *vdev) > > { > > - return virtio_has_feature(vdev, VIRTIO_F_VERSION_1); > > + if (virtio_has_feature(vdev, VIRTIO_F_VERSION_1)) > > + return true; > > + return virtio_legacy_is_little_endian(); > > } > > > > /* Memory accessors */ > > diff --git a/include/linux/vringh.h b/include/linux/vringh.h > > index 3ed62ef..d786c2d 100644 > > --- a/include/linux/vringh.h > > +++ b/include/linux/vringh.h > > @@ -228,7 +228,9 @@ static inline void vringh_notify(struct vringh *vrh) > > > > static inline bool vringh_is_little_endian(const struct vringh *vrh) > > { > > - return vrh->little_endian; > > + if (vrh->little_endian) > > + return true; > > + return virtio_legacy_is_little_endian(); > > } > > > > static inline u16 vringh16_to_cpu(const struct vringh *vrh, __virtio16 val) >