On Wed, 22 Oct 2014 21:44:08 +0300
"Michael S. Tsirkin" <mst@xxxxxxxxxx> wrote:
> virtio 1.0 makes all memory structures LE, so
> we need APIs to conditionally do a byteswap on BE
> architectures.
>
> To make it easier to check code statically,
> add virtio specific types for multi-byte integers
> in memory.
>
> Add low level wrappers that do a byteswap conditionally, these will be
> useful e.g. for vhost. Add high level wrappers that will (in the
> future) query device endian-ness and act accordingly.
>
> At the moment, stub them out and assume native endian-ness everywhere.
>
> Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
> ---
> include/linux/virtio_byteorder.h | 29 ++++++++++++++++++++++++
> include/linux/virtio_config.h | 16 +++++++++++++
> include/uapi/linux/virtio_ring.h | 49 ++++++++++++++++++++--------------------
> include/uapi/linux/Kbuild | 1 +
> 4 files changed, 71 insertions(+), 24 deletions(-)
> create mode 100644 include/linux/virtio_byteorder.h
>
> diff --git a/include/linux/virtio_byteorder.h b/include/linux/virtio_byteorder.h
> new file mode 100644
> index 0000000..7afdd8a
> --- /dev/null
> +++ b/include/linux/virtio_byteorder.h
> @@ -0,0 +1,29 @@
> +#ifndef _LINUX_VIRTIO_BYTEORDER_H
> +#define _LINUX_VIRTIO_BYTEORDER_H
> +#include <linux/types.h>
> +#include <uapi/linux/virtio_types.h>
> +
> +/* Memory accessors for handling virtio in modern little endian and in
> + * compatibility big endian format. */
s/big/native/
> +
> +#define __DEFINE_VIRTIO_XX_TO_CPU(bits) \
> +static inline u##bits __virtio##bits##_to_cpu(bool little_endian, __virtio##bits val) \
> +{ \
> + if (little_endian) \
> + return le##bits##_to_cpu((__force __le##bits)val); \
> + else \
> + return (__force u##bits)val; \
> +} \
> +static inline __virtio##bits __cpu_to_virtio##bits(bool little_endian, u##bits val) \
> +{ \
> + if (little_endian) \
> + return (__force __virtio##bits)cpu_to_le##bits(val); \
> + else \
> + return val; \
> +}
> +
> +__DEFINE_VIRTIO_XX_TO_CPU(16)
> +__DEFINE_VIRTIO_XX_TO_CPU(32)
> +__DEFINE_VIRTIO_XX_TO_CPU(64)
...although I'm still not too happy with macro-generated helpers.
> +
> +#endif /* _LINUX_VIRTIO_BYTEORDER */
> diff --git a/include/uapi/linux/virtio_ring.h b/include/uapi/linux/virtio_ring.h
> index a99f9b7..6c00632 100644
> --- a/include/uapi/linux/virtio_ring.h
> +++ b/include/uapi/linux/virtio_ring.h
> @@ -61,32 +62,32 @@
> /* Virtio ring descriptors: 16 bytes. These can chain together via "next". */
> struct vring_desc {
> /* Address (guest-physical). */
> - __u64 addr;
> + __virtio64 addr;
> /* Length. */
> - __u32 len;
> + __virtio32 len;
> /* The flags as indicated above. */
> - __u16 flags;
> + __virtio16 flags;
> /* We chain unused descriptors via this, too */
> - __u16 next;
> + __virtio16 next;
> };
I think all of these __virtio types need an explanation somewhere as to
what they mean, e.g.:
/*
* __virtio{16,32,64} have the following meaning:
* - __u{16,32,64} for virtio devices in legacy mode,
* accessed in native endian
* - __le{16,32,64} for standard-compliant virtio devices
*/
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