[PATCH v2 3/6] crypto: x86/chacha20 - limit the preemption-disabled section

Eric Biggers
2018-11-30T10:10:34Z

From: Eric Biggers <ebiggers@google.com>

To improve responsiveness, disable preemption for each step of the walk
(which is at most PAGE_SIZE) rather than for the entire
encryption/decryption operation.

Signed-off-by: Eric Biggers <ebiggers@google.com>
---
arch/x86/crypto/chacha20_glue.c | 8 +++-----
1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/arch/x86/crypto/chacha20_glue.c b/arch/x86/crypto/chacha20_glue.c
index 773d075a1483..036de144aab6 100644
--- a/arch/x86/crypto/chacha20_glue.c
+++ b/arch/x86/crypto/chacha20_glue.c
@@ -135,26 +135,24 @@ static int chacha20_simd(struct skcipher_request *req)
if (req->cryptlen <= CHACHA_BLOCK_SIZE || !may_use_simd())
return crypto_chacha_crypt(req);

- err = skcipher_walk_virt(&walk, req, true);
+ err = skcipher_walk_virt(&walk, req, false);

crypto_chacha_init(state, ctx, walk.iv);

- kernel_fpu_begin();
-
while (walk.nbytes > 0) {
unsigned int nbytes = walk.nbytes;

if (nbytes < walk.total)
nbytes = round_down(nbytes, walk.stride);

+ kernel_fpu_begin();
chacha20_dosimd(state, walk.dst.virt.addr, walk.src.virt.addr,
nbytes);
+ kernel_fpu_end();

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

- kernel_fpu_end();
-
return err;
}

--
2.20.0.rc0.387.gc7a69e6b6c-goog