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 at redhat.com> 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
On Mon, Nov 24, 2014 at 1:15 PM, Michael S. Tsirkin <mst at redhat.com> wrote:> 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 at redhat.com> 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.IC, that was not clear from the description for this patch. I thought it was dependent on BE architectures. Nevertheless, any chance you can get rid of the "conditional"? Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
On Mon, Nov 24, 2014 at 01:58:43PM +0100, Geert Uytterhoeven wrote:> On Mon, Nov 24, 2014 at 1:15 PM, Michael S. Tsirkin <mst at redhat.com> wrote: > > 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 at redhat.com> 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. > > IC, that was not clear from the description for this patch. > I thought it was dependent on BE architectures. > > Nevertheless, any chance you can get rid of the "conditional"?I don't see how - this is fundamental to any virtio device that wants to support both 0.9 and 1.0 from the same codebase.> Gr{oetje,eeting}s, > > Geert > > -- > Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org > > In personal conversations with technical people, I call myself a hacker. But > when I'm talking to journalists I just say "programmer" or something like that. > -- Linus Torvalds