virtio: add explicit big-endian support to memory accessors

gkurz · mstsirkin · commit 7d82410950aa · 2015-06-01T15:48:54.000+02:00
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 &lt;gkurz@linux.vnet.ibm.com&gt;

Signed-off-by: Michael S. Tsirkin &lt;mst@redhat.com&gt;
Reviewed-by: Cornelia Huck &lt;cornelia.huck@de.ibm.com&gt;
Reviewed-by: David Gibson &lt;david@gibson.dropbear.id.au&gt;
diff --git 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
@@ -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
@@ -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
@@ -3,57 +3,61 @@
 #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)
 {
 	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)
 {
 	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)
 {
 	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)
 {
 	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)
 {
 	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
@@ -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
@@ -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)

Original file line number	Diff line number	Diff line change
`@@ -51,7 +51,8 @@ struct macvtap_queue {`
`51`	`51`
`52`	`52`	`static inline bool macvtap_is_little_endian(struct macvtap_queue *q)`
`53`	`53`	`{`
`54`		`- return q->flags & MACVTAP_VNET_LE;`
	`54`	`+ return q->flags & MACVTAP_VNET_LE \|\|`
	`55`	`+ virtio_legacy_is_little_endian();`
`55`	`56`	`}`
`56`	`57`
`57`	`58`	`static inline u16 macvtap16_to_cpu(struct macvtap_queue *q, __virtio16 val)`
Original file line number	Diff line number	Diff line change
`@@ -208,7 +208,8 @@ struct tun_struct {`
`208`	`208`
`209`	`209`	`static inline bool tun_is_little_endian(struct tun_struct *tun)`
`210`	`210`	`{`
`211`		`- return tun->flags & TUN_VNET_LE;`
	`211`	`+ return tun->flags & TUN_VNET_LE \|\|`
	`212`	`+ virtio_legacy_is_little_endian();`
`212`	`213`	`}`
`213`	`214`
`214`	`215`	`static inline u16 tun16_to_cpu(struct tun_struct *tun, __virtio16 val)`
Original file line number	Diff line number	Diff line change
`@@ -175,7 +175,8 @@ static inline bool vhost_has_feature(struct vhost_virtqueue *vq, int bit)`
`175`	`175`
`176`	`176`	`static inline bool vhost_is_little_endian(struct vhost_virtqueue *vq)`
`177`	`177`	`{`
`178`		`- return vhost_has_feature(vq, VIRTIO_F_VERSION_1);`
	`178`	`+ return vhost_has_feature(vq, VIRTIO_F_VERSION_1) \|\|`
	`179`	`+ virtio_legacy_is_little_endian();`
`179`	`180`	`}`
`180`	`181`
`181`	`182`	`/* Memory accessors */`
Original file line number	Diff line number	Diff line change
`@@ -3,57 +3,61 @@`
`3`	`3`	`#include <linux/types.h>`
`4`	`4`	`#include <uapi/linux/virtio_types.h>`
`5`	`5`
`6`		`-/*`
`7`		`- * Low-level memory accessors for handling virtio in modern little endian and in`
`8`		`- * compatibility native endian format.`
`9`		`- */`
	`6`	`+static inline bool virtio_legacy_is_little_endian(void)`
	`7`	`+{`
	`8`	`+#ifdef __LITTLE_ENDIAN`
	`9`	`+ return true;`
	`10`	`+#else`
	`11`	`+ return false;`
	`12`	`+#endif`
	`13`	`+}`
`10`	`14`
`11`	`15`	`static inline u16 __virtio16_to_cpu(bool little_endian, __virtio16 val)`
`12`	`16`	`{`
`13`	`17`	`if (little_endian)`
`14`	`18`	`return le16_to_cpu((__force __le16)val);`
`15`	`19`	`else`
`16`		`- return (__force u16)val;`
	`20`	`+ return be16_to_cpu((__force __be16)val);`
`17`	`21`	`}`
`18`	`22`
`19`	`23`	`static inline __virtio16 __cpu_to_virtio16(bool little_endian, u16 val)`
`20`	`24`	`{`
`21`	`25`	`if (little_endian)`
`22`	`26`	`return (__force __virtio16)cpu_to_le16(val);`
`23`	`27`	`else`
`24`		`- return (__force __virtio16)val;`
	`28`	`+ return (__force __virtio16)cpu_to_be16(val);`
`25`	`29`	`}`
`26`	`30`
`27`	`31`	`static inline u32 __virtio32_to_cpu(bool little_endian, __virtio32 val)`
`28`	`32`	`{`
`29`	`33`	`if (little_endian)`
`30`	`34`	`return le32_to_cpu((__force __le32)val);`
`31`	`35`	`else`
`32`		`- return (__force u32)val;`
	`36`	`+ return be32_to_cpu((__force __be32)val);`
`33`	`37`	`}`
`34`	`38`
`35`	`39`	`static inline __virtio32 __cpu_to_virtio32(bool little_endian, u32 val)`
`36`	`40`	`{`
`37`	`41`	`if (little_endian)`
`38`	`42`	`return (__force __virtio32)cpu_to_le32(val);`
`39`	`43`	`else`
`40`		`- return (__force __virtio32)val;`
	`44`	`+ return (__force __virtio32)cpu_to_be32(val);`
`41`	`45`	`}`
`42`	`46`
`43`	`47`	`static inline u64 __virtio64_to_cpu(bool little_endian, __virtio64 val)`
`44`	`48`	`{`
`45`	`49`	`if (little_endian)`
`46`	`50`	`return le64_to_cpu((__force __le64)val);`
`47`	`51`	`else`
`48`		`- return (__force u64)val;`
	`52`	`+ return be64_to_cpu((__force __be64)val);`
`49`	`53`	`}`
`50`	`54`
`51`	`55`	`static inline __virtio64 __cpu_to_virtio64(bool little_endian, u64 val)`
`52`	`56`	`{`
`53`	`57`	`if (little_endian)`
`54`	`58`	`return (__force __virtio64)cpu_to_le64(val);`
`55`	`59`	`else`
`56`		`- return (__force __virtio64)val;`
	`60`	`+ return (__force __virtio64)cpu_to_be64(val);`
`57`	`61`	`}`
`58`	`62`
`59`	`63`	`#endif /* _LINUX_VIRTIO_BYTEORDER */`
Original file line number	Diff line number	Diff line change
`@@ -207,7 +207,8 @@ int virtqueue_set_affinity(struct virtqueue *vq, int cpu)`
`207`	`207`
`208`	`208`	`static inline bool virtio_is_little_endian(struct virtio_device *vdev)`
`209`	`209`	`{`
`210`		`- return virtio_has_feature(vdev, VIRTIO_F_VERSION_1);`
	`210`	`+ return virtio_has_feature(vdev, VIRTIO_F_VERSION_1) \|\|`
	`211`	`+ virtio_legacy_is_little_endian();`
`211`	`212`	`}`
`212`	`213`
`213`	`214`	`/* Memory accessors */`
Original file line number	Diff line number	Diff line change
`@@ -228,7 +228,8 @@ static inline void vringh_notify(struct vringh *vrh)`
`228`	`228`
`229`	`229`	`static inline bool vringh_is_little_endian(const struct vringh *vrh)`
`230`	`230`	`{`
`231`		`- return vrh->little_endian;`
	`231`	`+ return vrh->little_endian \|\|`
	`232`	`+ virtio_legacy_is_little_endian();`
`232`	`233`	`}`
`233`	`234`
`234`	`235`	`static inline u16 vringh16_to_cpu(const struct vringh *vrh, __virtio16 val)`