Re: [PATCH v2 03/24] virtio: allow __virtioXX, __leXX in config space

Currently all config space fields are of the type __uXX.
This confuses people and some drivers (notably vdpa)
access them using CPU endian-ness - which only
works well for legacy or LE platforms.

Update virtio_cread/virtio_cwrite macros to allow __virtioXX
and __leXX field types. Follow-up patches will convert
config space to use these types.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
  include/linux/virtio_config.h | 50 +++++++++++++++++++++++++++++++++--
  1 file changed, 48 insertions(+), 2 deletions(-)

diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
index 3b4eae5ac5e3..64da491936f7 100644
--- a/include/linux/virtio_config.h
+++ b/include/linux/virtio_config.h

@@ -6,6 +6,7 @@
  #include <linux/bug.h>
  #include <linux/virtio.h>
  #include <linux/virtio_byteorder.h>
+#include <linux/compiler_types.h>
  #include <uapi/linux/virtio_config.h>
  
  struct irq_affinity;

@@ -287,12 +288,57 @@ static inline __virtio64 cpu_to_virtio64(struct virtio_device *vdev, u64 val)
  	return __cpu_to_virtio64(virtio_is_little_endian(vdev), val);
  }
  
+/*
+ * Only the checker differentiates between __virtioXX and __uXX types. But we
+ * try to share as much code as we can with the regular GCC build.
+ */
+#if !defined(CONFIG_CC_IS_GCC) && !defined(__CHECKER__)
+
+/* Not a checker - we can keep things simple */
+#define __virtio_native_typeof(x) typeof(x)
+
+#else
+
+/*
+ * We build this out of a couple of helper macros in a vain attempt to
+ * help you keep your lunch down while reading it.
+ */
+#define __virtio_pick_value(x, type, then, otherwise)			\
+	__builtin_choose_expr(__same_type(x, type), then, otherwise)
+
+#define __virtio_pick_type(x, type, then, otherwise)			\
+	__virtio_pick_value(x, type, (then)0, otherwise)
+
+#define __virtio_pick_endian(x, x16, x32, x64, otherwise)			\
+	__virtio_pick_type(x, x16, __u16,					\
+		__virtio_pick_type(x, x32, __u32,				\
+			__virtio_pick_type(x, x64, __u64,			\
+				otherwise)))
+
+#define __virtio_native_typeof(x) typeof(					\
+	__virtio_pick_type(x, __u8, __u8,					\
+		__virtio_pick_endian(x, __virtio16, __virtio32, __virtio64,	\
+			__virtio_pick_endian(x, __le16, __le32, __le64,		\
+				__virtio_pick_endian(x, __u16, __u32, __u64,	\
+					/* No other type allowed */		\
+					(void)0)))))
+
+#endif
+
+#define __virtio_native_type(structname, member) \
+	__virtio_native_typeof(((structname*)0)->member)
+
+#define __virtio_typecheck(structname, member, val) \
+		/* Must match the member's type, and be integer */ \
+		typecheck(__virtio_native_type(structname, member), (val))
+
+
  /* Config space accessors. */
  #define virtio_cread(vdev, structname, member, ptr)			\
  	do {								\
  		might_sleep();						\
  		/* Must match the member's type, and be integer */	\
-		if (!typecheck(typeof((((structname*)0)->member)), *(ptr))) \
+		if (!__virtio_typecheck(structname, member, *(ptr)))	\
  			(*ptr) = 1;					\

  									\
  		switch (sizeof(*ptr)) {					\

@@ -322,7 +368,7 @@ static inline __virtio64 cpu_to_virtio64(struct virtio_device *vdev, u64 val)
  	do {								\
  		might_sleep();						\
  		/* Must match the member's type, and be integer */	\
-		if (!typecheck(typeof((((structname*)0)->member)), *(ptr))) \
+		if (!__virtio_typecheck(structname, member, *(ptr)))	\
  			BUG_ON((*ptr) == 1);				\
  									\
  		switch (sizeof(*ptr)) {					\