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UPSTREAM: crypto: x86/chacha - yield the FPU occasionally

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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: Martin Willi <martin@strongswan.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
(cherry picked from commit a033aed5a8)
Bug: 152722841
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: Ic6910b498e9cfec0deecf00ef787a9453fec4616
This commit is contained in:
Eric Biggers
2018-12-04 22:20:05 -08:00
committed by Greg Kroah-Hartman
parent c4d866c3ae
commit f03b06c3b9
1 changed files with 11 additions and 1 deletions
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12
arch/x86/crypto/chacha_glue.c
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@@ -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);
}