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crypto: arm64/sha256-neon - play nice with CONFIG_PREEMPT kernels

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Tweak the SHA256 update routines to invoke the SHA256 block transform
block by block, to avoid excessive scheduling delays caused by the
NEON algorithm running with preemption disabled.

Also, remove a stale comment which no longer applies now that kernel
mode NEON is actually disallowed in some contexts.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Ard Biesheuvel 2018-03-10 15:21:54 +00:00 committed by Herbert Xu
parent 870c163a0e
commit 1a3713c7cd
1 changed files with 23 additions and 13 deletions
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36
arch/arm64/crypto/sha256-glue.c
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@ -89,21 +89,32 @@ static struct shash_alg algs[] = { {
static int sha256_update_neon(struct shash_desc *desc, const u8 *data, static int sha256_update_neon(struct shash_desc *desc, const u8 *data,
unsigned int len) unsigned int len)
{ {
/* struct sha256_state *sctx = shash_desc_ctx(desc);
* Stacking and unstacking a substantial slice of the NEON register
* file may significantly affect performance for small updates when
* executing in interrupt context, so fall back to the scalar code
* in that case.
*/
if (!may_use_simd()) if (!may_use_simd())
return sha256_base_do_update(desc, data, len, return sha256_base_do_update(desc, data, len,
(sha256_block_fn *)sha256_block_data_order); (sha256_block_fn *)sha256_block_data_order);
kernel_neon_begin(); while (len > 0) {
sha256_base_do_update(desc, data, len, unsigned int chunk = len;
(sha256_block_fn *)sha256_block_neon);
kernel_neon_end();
/*
* Don't hog the CPU for the entire time it takes to process all
* input when running on a preemptible kernel, but process the
* data block by block instead.
*/
if (IS_ENABLED(CONFIG_PREEMPT) &&
chunk + sctx->count % SHA256_BLOCK_SIZE > SHA256_BLOCK_SIZE)
chunk = SHA256_BLOCK_SIZE -
sctx->count % SHA256_BLOCK_SIZE;
kernel_neon_begin();
sha256_base_do_update(desc, data, chunk,
(sha256_block_fn *)sha256_block_neon);
kernel_neon_end();
data += chunk;
len -= chunk;
}
return 0; return 0;
} }
@ -117,10 +128,9 @@ static int sha256_finup_neon(struct shash_desc *desc, const u8 *data,
sha256_base_do_finalize(desc, sha256_base_do_finalize(desc,
(sha256_block_fn *)sha256_block_data_order); (sha256_block_fn *)sha256_block_data_order);
} else { } else {
kernel_neon_begin();
if (len) if (len)
sha256_base_do_update(desc, data, len, sha256_update_neon(desc, data, len);
(sha256_block_fn *)sha256_block_neon); kernel_neon_begin();
sha256_base_do_finalize(desc, sha256_base_do_finalize(desc,
(sha256_block_fn *)sha256_block_neon); (sha256_block_fn *)sha256_block_neon);
kernel_neon_end(); kernel_neon_end();