On Mon, Nov 24, 2014 at 01:03:24PM +0100, Geert Uytterhoeven wrote:
> On Mon, Nov 24, 2014 at 12:52 PM, 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
> > query device endian-ness and act accordingly.
>
> > diff --git a/include/linux/virtio_byteorder.h b/include/linux/virtio_byteorder.h
> > new file mode 100644
> > index 0000000..824ed0b
> > --- /dev/null
> > +++ b/include/linux/virtio_byteorder.h
>
> > +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;
> > +}
>
> What's wrong with just using le16-to_cpu() ...
le16-to_cpu() is simply wrong: virtio needs to be
LE or native endian, depending on whether it's running
in 0.9 or 1.0 mode.
> > --- a/include/uapi/linux/virtio_ring.h
> > +++ b/include/uapi/linux/virtio_ring.h
>
> > /* Virtio ring descriptors: 16 bytes. These can chain together via "next". */
> > struct vring_desc {
> > /* Address (guest-physical). */
> > - __u64 addr;
> > + __virtio64 addr;
>
> ... and __le64?
>
> There's already lots of precedence or this, even in include/uapi/.
>
> Gr{oetje,eeting}s,
>
> Geert
__le would make people think they can use le16-to_cpu() which is wrong.
--
MST
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