Re: [PATCH 1/5] lib/crc: arm64: Drop unnecessary chunking logic from crc64

Eric Biggers
2026-03-31T22:33:02Z

On Mon, Mar 30, 2026 at 04:46:32PM +0200, Ard Biesheuvel wrote:
> On arm64, kernel mode NEON executes with preemption enabled, so there is
> no need to chunk the input by hand.
>
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

There's still similar "chunking" in other arm64 code:

$ git grep -E 'SZ_4K|cond_yield' lib/crypto/arm64
lib/crypto/arm64/chacha.h: unsigned int todo = min_t(unsigned int, bytes, SZ_4K);
lib/crypto/arm64/poly1305.h: unsigned int todo = min_t(unsigned int, len, SZ_4K);
lib/crypto/arm64/sha1-ce-core.S: cond_yield 1f, x5, x6
lib/crypto/arm64/sha256-ce.S: cond_yield 1f, x5, x6
lib/crypto/arm64/sha3-ce-core.S: cond_yield 4f, x8, x9
lib/crypto/arm64/sha512-ce-core.S: cond_yield 3f, x4, x5

I thought it was still sticking around, despite kernel-mode NEON now
being preemptible on arm64, because of CONFIG_PREEMPT_VOLUNTARY.

However, I see that support for CONFIG_PREEMPT_VOLUNTARY was recently
removed on arm64. So that's what finally makes this no longer needed,
and we can now clean up these other cases too, right?

(Though, I can't find where the voluntary preemption points actually
were. So maybe they weren't actually there anyway.)

- Eric