Re: [PATCH v2 06/18] crypto: rockchip: add fallback for cipher

[John Keeping]

On Wed, Mar 02, 2022 at 09:11:01PM +0000, Corentin Labbe wrote:
> The hardware does not handle 0 size length request, let's add a
> fallback.
> Furthermore fallback will be used for all unaligned case the hardware
> cannot handle.
> 
> Fixes: ce0183cb6464b ("crypto: rockchip - switch to skcipher API")
> Signed-off-by: Corentin Labbe <clabbe@xxxxxxxxxxxx>
> ---
>  drivers/crypto/rockchip/rk3288_crypto.h       |  2 +
>  .../crypto/rockchip/rk3288_crypto_skcipher.c  | 97 ++++++++++++++++---
>  2 files changed, 86 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/crypto/rockchip/rk3288_crypto.h b/drivers/crypto/rockchip/rk3288_crypto.h
> index c919d9a43a08..8b1e15d8ddc6 100644
> --- a/drivers/crypto/rockchip/rk3288_crypto.h
> +++ b/drivers/crypto/rockchip/rk3288_crypto.h
> @@ -246,10 +246,12 @@ struct rk_cipher_ctx {
>  	struct rk_crypto_info		*dev;
>  	unsigned int			keylen;
>  	u8				iv[AES_BLOCK_SIZE];
> +	struct crypto_skcipher *fallback_tfm;
>  };
>  
>  struct rk_cipher_rctx {
>  	u32				mode;
> +	struct skcipher_request fallback_req;   // keep at the end
>  };
>  
>  enum alg_type {
> diff --git a/drivers/crypto/rockchip/rk3288_crypto_skcipher.c b/drivers/crypto/rockchip/rk3288_crypto_skcipher.c
> index bbd0bf52bf07..bf9d398cc54c 100644
> --- a/drivers/crypto/rockchip/rk3288_crypto_skcipher.c
> +++ b/drivers/crypto/rockchip/rk3288_crypto_skcipher.c
> @@ -13,6 +13,63 @@
>  
>  #define RK_CRYPTO_DEC			BIT(0)
>  
> +static int rk_cipher_need_fallback(struct skcipher_request *req)
> +{
> +	struct scatterlist *sgs, *sgd;
> +
> +	if (!req->cryptlen)
> +		return true;
> +
> +	sgs = req->src;
> +	while (sgs) {
> +		if (!IS_ALIGNED(sgs->offset, sizeof(u32))) {
> +			return true;
> +		}
> +		if (sgs->length % 16) {

Can this be relaxed to check for alignment to 4 rather than 16?  That's
the requirement for programming the registers.

But I think this check is wrong in general as it doesn't account for
cryptlen; with fscrypt I'm seeing sgs->length == 255 but cryptlen == 16
so the hardware can be used but at the moment the fallback path is
triggered.