[PATCH v5 09/23] crypto: arm64/sha256-neon - play nice with CONFIG_PREEMPT kernels
From: Ard Biesheuvel <hidden>
Date: 2018-03-10 15:21:54
Also in:
linux-crypto, linux-rt-users
Subsystem:
arm64 port (aarch64 architecture), the rest · Maintainers:
Catalin Marinas, Will Deacon, Linus Torvalds
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 <redacted> --- arch/arm64/crypto/sha256-glue.c | 36 +++++++++++++------- 1 file changed, 23 insertions(+), 13 deletions(-)
diff --git a/arch/arm64/crypto/sha256-glue.c b/arch/arm64/crypto/sha256-glue.c
index b064d925fe2a..e8880ccdc71f 100644
--- a/arch/arm64/crypto/sha256-glue.c
+++ b/arch/arm64/crypto/sha256-glue.c@@ -89,21 +89,32 @@ static struct shash_alg algs[] = { { static int sha256_update_neon(struct shash_desc *desc, const u8 *data, unsigned int len) { - /* - * 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. - */ + struct sha256_state *sctx = shash_desc_ctx(desc); + if (!may_use_simd()) return sha256_base_do_update(desc, data, len, (sha256_block_fn *)sha256_block_data_order); - kernel_neon_begin(); - sha256_base_do_update(desc, data, len, - (sha256_block_fn *)sha256_block_neon); - kernel_neon_end(); + while (len > 0) { + unsigned int chunk = len; + + /* + * 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; }
@@ -117,10 +128,9 @@ static int sha256_finup_neon(struct shash_desc *desc, const u8 *data, sha256_base_do_finalize(desc, (sha256_block_fn *)sha256_block_data_order); } else { - kernel_neon_begin(); if (len) - sha256_base_do_update(desc, data, len, - (sha256_block_fn *)sha256_block_neon); + sha256_update_neon(desc, data, len); + kernel_neon_begin(); sha256_base_do_finalize(desc, (sha256_block_fn *)sha256_block_neon); kernel_neon_end();
--
2.15.1