Re: [PATCH] crypto: x86: Do not acquire fpu context for too long

[Herbert Xu <herbert@gondor.apana.org.au>]

On Tue, Oct 04, 2022 at 04:49:12AM +0000, Taehee Yoo wrote:
>
>  #define ECB_WALK_START(req, bsize, fpu_blocks) do {			\
>  	void *ctx = crypto_skcipher_ctx(crypto_skcipher_reqtfm(req));	\
> +	unsigned int walked_bytes = 0;					\
>  	const int __bsize = (bsize);					\
>  	struct skcipher_walk walk;					\
> -	int err = skcipher_walk_virt(&walk, (req), false);		\
> +	int err;							\
> +									\
> +	err = skcipher_walk_virt(&walk, (req), false);			\
>  	while (walk.nbytes > 0) {					\
> -		unsigned int nbytes = walk.nbytes;			\
> -		bool do_fpu = (fpu_blocks) != -1 &&			\
> -			      nbytes >= (fpu_blocks) * __bsize;		\
>  		const u8 *src = walk.src.virt.addr;			\
> -		u8 *dst = walk.dst.virt.addr;				\
>  		u8 __maybe_unused buf[(bsize)];				\
> -		if (do_fpu) kernel_fpu_begin()
> +		u8 *dst = walk.dst.virt.addr;				\
> +		unsigned int nbytes;					\
> +		bool do_fpu;						\
> +									\
> +		if (walk.nbytes - walked_bytes > ECB_CBC_WALK_MAX) {	\
> +			nbytes = ECB_CBC_WALK_MAX;			\
> +			walked_bytes += ECB_CBC_WALK_MAX;		\
> +		} else {						\
> +			nbytes = walk.nbytes - walked_bytes;		\
> +			walked_bytes = walk.nbytes;			\
> +		}							\
> +									\
> +		do_fpu = (fpu_blocks) != -1 &&				\
> +			 nbytes >= (fpu_blocks) * __bsize;		\
> +		if (do_fpu)						\
> +			kernel_fpu_begin()
>  
>  #define CBC_WALK_START(req, bsize, fpu_blocks)				\
>  	ECB_WALK_START(req, bsize, fpu_blocks)
> @@ -65,8 +81,12 @@
>  } while (0)
>  
>  #define ECB_WALK_END()							\
> -		if (do_fpu) kernel_fpu_end();				\
> +		if (do_fpu)						\
> +			kernel_fpu_end();				\
> +		if (walked_bytes < walk.nbytes)				\
> +			continue;					\
>  		err = skcipher_walk_done(&walk, nbytes);		\
> +		walked_bytes = 0;					\
>  	}								\
>  	return err;							\
>  } while (0)

skcipher_walk_* is supposed to return at most a page.  Why is this
necessary?

Cheers,
-- 
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt