On Thu, Oct 23, 2014 at 09:54:05AM +0200, Cornelia Huck wrote:
> 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/
Thanks.
> > +
> > +#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.
I'm fine with open-coding them.
> > +
> > +#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
> */
Will do.
--
MST
_______________________________________________
Virtualization mailing list
Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx
https://lists.linuxfoundation.org/mailman/listinfo/virtualization
