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Commit a033aed5 authored by Eric Biggers's avatar Eric Biggers Committed by Herbert Xu
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crypto: x86/chacha - yield the FPU occasionally 



To improve responsiveness, yield the FPU (temporarily re-enabling
preemption) every 4 KiB encrypted/decrypted, rather than keeping
preemption disabled during the entire encryption/decryption operation.

Alternatively we could do this for every skcipher_walk step, but steps
may be small in some cases, and yielding the FPU is expensive on x86.

Suggested-by: default avatarMartin Willi <martin@strongswan.org>
Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
parent 7a507d62

arch/x86/crypto/chacha_glue.c

+11 −1
Original line number Diff line number Diff line
@@ -132,6 +132,7 @@ static int chacha_simd_stream_xor(struct skcipher_request *req, 
{

	u32 *state, state_buf[16 + 2] __aligned(8);

	struct skcipher_walk walk;

	int next_yield = 4096; /* bytes until next FPU yield */

	int err;



	BUILD_BUG_ON(CHACHA_STATE_ALIGN != 16);
@@ -144,12 +145,21 @@ static int chacha_simd_stream_xor(struct skcipher_request *req, 
	while (walk.nbytes > 0) {

		unsigned int nbytes = walk.nbytes;



		if (nbytes < walk.total)

		if (nbytes < walk.total) {

			nbytes = round_down(nbytes, walk.stride);

			next_yield -= nbytes;

		}



		chacha_dosimd(state, walk.dst.virt.addr, walk.src.virt.addr,

			      nbytes, ctx->nrounds);



		if (next_yield <= 0) {

			/* temporarily allow preemption */

			kernel_fpu_end();

			kernel_fpu_begin();

			next_yield = 4096;

		}



		err = skcipher_walk_done(&walk, walk.nbytes - nbytes);

	}