Re: [PATCH crypto-stable] crypto: arch/lib - limit simd usage to PAGE_SIZE chunks

[Jason A. Donenfeld]

On Tue, Apr 21, 2020 at 10:04 PM Eric Biggers <ebiggers@xxxxxxxxxx> wrote:
> Seems this should just be a 'while' loop?
>
>         while (bytes) {
>                 unsigned int todo = min_t(unsigned int, PAGE_SIZE, bytes);
>
>                 kernel_neon_begin();
>                 chacha_doneon(state, dst, src, todo, nrounds);
>                 kernel_neon_end();
>
>                 bytes -= todo;
>                 src += todo;
>                 dst += todo;
>         }

The for(;;) is how it's done elsewhere in the kernel (that this patch
doesn't touch), because then we can break out of the loop before
having to increment src and dst unnecessarily. Likely a pointless
optimization as probably the compiler can figure out how to avoid
that. But maybe it can't. If you have a strong preference, I can
reactor everything to use `while (bytes)`, but if you don't care,
let's keep this as-is. Opinion?

Jason