On Wed, Oct 12, 2022 at 04:59:16PM -0500, Robert Elliott wrote:
> diff --git a/arch/x86/crypto/sha1_ssse3_glue.c b/arch/x86/crypto/sha1_ssse3_glue.c
> index 44340a1139e0..a9f5779b41ca 100644
> --- a/arch/x86/crypto/sha1_ssse3_glue.c
> +++ b/arch/x86/crypto/sha1_ssse3_glue.c
> @@ -26,6 +26,8 @@
> #include <crypto/sha1_base.h>
> #include <asm/simd.h>
>
> +#define FPU_BYTES 4096U /* avoid kernel_fpu_begin/end scheduler/rcu stalls */
> +
> static int sha1_update(struct shash_desc *desc, const u8 *data,
> unsigned int len, sha1_block_fn *sha1_xform)
> {
> @@ -41,9 +43,18 @@ static int sha1_update(struct shash_desc *desc, const u8 *data,
> */
> BUILD_BUG_ON(offsetof(struct sha1_state, state) != 0);
>
> - kernel_fpu_begin();
> - sha1_base_do_update(desc, data, len, sha1_xform);
> - kernel_fpu_end();
> + do {
> + unsigned int chunk = min(len, FPU_BYTES);
> +
> + if (chunk) {
> + kernel_fpu_begin();
> + sha1_base_do_update(desc, data, chunk, sha1_xform);
> + kernel_fpu_end();
> + }
> +
> + len -= chunk;
> + data += chunk;
> + } while (len);
'len' can't be 0 at the beginning of this loop, so the 'if (chunk)' check isn't
needed. And it wouldn't make sense even if 'len' could be 0, since a while loop
could just be used in that case.
- Eric
