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crypto: arch/lib - limit simd usage to 4k chunks

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The initial Zinc patchset, after some mailing list discussion, contained
code to ensure that kernel_fpu_enable would not be kept on for more than
a 4k chunk, since it disables preemption. The choice of 4k isn't totally
scientific, but it's not a bad guess either, and it's what's used in
both the x86 poly1305, blake2s, and nhpoly1305 code already (in the form
of PAGE_SIZE, which this commit corrects to be explicitly 4k for the
former two).

Ard did some back of the envelope calculations and found that
at 5 cycles/byte (overestimate) on a 1ghz processor (pretty slow), 4k
means we have a maximum preemption disabling of 20us, which Sebastian
confirmed was probably a good limit.

Unfortunately the chunking appears to have been left out of the final
patchset that added the glue code. So, this commit adds it back in.

Fixes: 84e03fa39f ("crypto: x86/chacha - expose SIMD ChaCha routine as library function")
Fixes: b3aad5bad2 ("crypto: arm64/chacha - expose arm64 ChaCha routine as library function")
Fixes: a44a3430d7 ("crypto: arm/chacha - expose ARM ChaCha routine as library function")
Fixes: d7d7b85356 ("crypto: x86/poly1305 - wire up faster implementations for kernel")
Fixes: f569ca1647 ("crypto: arm64/poly1305 - incorporate OpenSSL/CRYPTOGAMS NEON implementation")
Fixes: a6b803b3dd ("crypto: arm/poly1305 - incorporate OpenSSL/CRYPTOGAMS NEON implementation")
Fixes: ed0356eda1 ("crypto: blake2s - x86_64 SIMD implementation")
Cc: Eric Biggers <ebiggers@google.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: stable@vger.kernel.org
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Jason A. Donenfeld
2020-04-22 17:18:53 -06:00
committed by Herbert Xu
parent 55b3209acb
commit 706024a52c
7 changed files with 65 additions and 30 deletions
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10
arch/x86/crypto/blake2s-glue.c
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@@ -32,16 +32,16 @@ void blake2s_compress_arch(struct blake2s_state *state,
const u32 inc)
{
/* SIMD disables preemption, so relax after processing each page. */
BUILD_BUG_ON(PAGE_SIZE / BLAKE2S_BLOCK_SIZE < 8);
BUILD_BUG_ON(SZ_4K / BLAKE2S_BLOCK_SIZE < 8);
if (!static_branch_likely(&blake2s_use_ssse3) || !crypto_simd_usable()) {
blake2s_compress_generic(state, block, nblocks, inc);
return;
}
for (;;) {
do {
const size_t blocks = min_t(size_t, nblocks,
PAGE_SIZE / BLAKE2S_BLOCK_SIZE);
SZ_4K / BLAKE2S_BLOCK_SIZE);
kernel_fpu_begin();
if (IS_ENABLED(CONFIG_AS_AVX512) &&
@@ -52,10 +52,8 @@ void blake2s_compress_arch(struct blake2s_state *state,
kernel_fpu_end();
nblocks -= blocks;
if (!nblocks)
break;
block += blocks * BLAKE2S_BLOCK_SIZE;
}
} while (nblocks);
}
EXPORT_SYMBOL(blake2s_compress_arch);