On Mon, 19 Jan 2015 11:45:39 +0000 Peter Maydell <peter.mayd...@linaro.org> wrote:
> On 19 January 2015 at 11:35, Stefan Hajnoczi <stefa...@gmail.com> wrote: > > What is the difference between the virtio_tswaps() and > > virtio_ld/st_p() families of functions? > > virtio_ld/st*_p() perform a load or store from memory pointed > to by the (host) pointer argument. > > virtio_tswap16 &c take a value, swap it as appropriate and > return a value. > > virtio_tswap16s &c do an in-place byteswap on the value pointed > to by the host pointer argument. > > (The tswap*/tswap*s pairs are a mirror of the equivalent families > of functions bswap16/bswap16s provided by bswap.h.) > > The most important distinction here is that the ld/st functions > will handle possibly unaligned accesses, whereas the tswap > functions will not. The former are intended for "fish this value > out from some guest RAM" and the latter for "we have a structure > we've copied from guest RAM already via memcpy and want to swizzle > the entries in it". > > -- PMM > Heh, not sure I would have provided such a comprehensive answer. :) Stefan, Feeling curious, what was the intent behind your question ? Cheers. -- Greg
