virtio: add explicit big-endian support to memory accessors

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@linux.vnet.ibm.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index 4fdb881..072ccba 100644 (file)
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -51,7 +51,8 @@ struct macvtap_queue {
 
 static inline bool macvtap_is_little_endian(struct macvtap_queue *q)
 {
-       return q->flags & MACVTAP_VNET_LE;
+       return q->flags & MACVTAP_VNET_LE ||
+               virtio_legacy_is_little_endian();
 }
 
 static inline u16 macvtap16_to_cpu(struct macvtap_queue *q, __virtio16 val)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 301e87c..b210139 100644 (file)
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -208,7 +208,8 @@ struct tun_struct {
 
 static inline bool tun_is_little_endian(struct tun_struct *tun)
 {
-       return tun->flags & TUN_VNET_LE;
+       return tun->flags & TUN_VNET_LE ||
+               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..a4fa33a 100644 (file)
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -175,7 +175,8 @@ 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) ||
+               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 (file)
--- a/include/linux/virtio_byteorder.h
+++ b/include/linux/virtio_byteorder.h
@@ -3,17 +3,21 @@
 #include <linux/types.h>
 #include <uapi/linux/virtio_types.h>
 
-/*
- * 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 170947e..e5ce8ab 100644 (file)
--- a/include/linux/virtio_config.h
+++ b/include/linux/virtio_config.h
@@ -207,7 +207,8 @@ 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);
+       return virtio_has_feature(vdev, VIRTIO_F_VERSION_1) ||
+               virtio_legacy_is_little_endian();
 }
 
 /* Memory accessors */

diff --git a/include/linux/vringh.h b/include/linux/vringh.h
index 3ed62ef..bc6c28d 100644 (file)
--- a/include/linux/vringh.h
+++ b/include/linux/vringh.h
@@ -228,7 +228,8 @@ static inline void vringh_notify(struct vringh *vrh)
 
 static inline bool vringh_is_little_endian(const struct vringh *vrh)
 {
-       return vrh->little_endian;
+       return vrh->little_endian ||
+               virtio_legacy_is_little_endian();
 }
 
 static inline u16 vringh16_to_cpu(const struct vringh *vrh, __virtio16 val)