On Mon, 20 Sept 2021 at 23:46, Toke Høiland-Jørgensen <toke@xxxxxxxxxx> wrote:
> > The draft API was:
> >
> > void *xdp_mb_pointer_flush(struct xdp_buff *xdp_md, u32 flags,
> > u32 offset, u32 len, void *stack_buf)
> >
> > Which does not take the ptr returned by header_pointer(), but that's
> > easy to add (well, easy other than the fact it'd be the 6th arg).
>
> I guess we could play some trickery with stuffing offset/len/flags into
> one or two u64s to save an argument or two?
Adding another pointer arg seems really hard to explain as an API.
What happens if I pass the "wrong" ptr? What happens if I pass NULL?
How about this: instead of taking stack_ptr, take the return value
from header_pointer as an argument. Then use the already existing
(right ;P) inlining to do the following:
if (md->ptr + args->off != ret_ptr)
__pointer_flush(...)
This means that __pointer_flush has to deal with aliased memory
though, so it would always have to memmove. Probably OK for the "slow"
path?
Lorenz
--
Lorenz Bauer | Systems Engineer
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