linux-kernel - Re: [PATCH RESEND] crypto: sun8i-ss: do not use sg_dma

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Message-ID: <e147c220-92e1-40cb-920b-916cf6703b40@gmail.com>
Date: Sun, 27 Apr 2025 21:23:40 +0300
From: Ovidiu Panait <ovidiu.panait.oss@...il.com>
To: Corentin Labbe <clabbe.montjoie@...il.com>, herbert@...dor.apana.org.au,
 jernej.skrabec@...il.com, samuel@...lland.org, wens@...e.org
Cc: linux-arm-kernel@...ts.infradead.org, linux-crypto@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-sunxi@...ts.linux.dev
Subject: Re: [PATCH RESEND] crypto: sun8i-ss: do not use sg_dma_len before
 calling DMA functions

Hi,

On 4/27/25 2:12 PM, Corentin Labbe wrote:
> When testing sun8i-ss with multi_v7_defconfig, all CBC algorithm fail crypto
> selftests.
> This is strange since on sunxi_defconfig, everything was ok.
> The problem was in the IV setup loop which never run because sg_dma_len
> was 0.
> 
> Fixes: 359e893e8af4 ("crypto: sun8i-ss - rework handling of IV")
> Signed-off-by: Corentin Labbe <clabbe.montjoie@...il.com>
> ---
> 
> If someone know why sunxi_defconfig have sg_dma_len() which always works
> even with any DMA call not done.
> 

It seems that sunxi_defconfig has CONFIG_NEED_SG_DMA_LENGTH disabled, so
sg_dma_len() defaults to sg->length.

>From include/linux/scatterlist.h:

/*
 * These macros should be used after a dma_map_sg call has been done
 * to get bus addresses of each of the SG entries and their lengths.
 * You should only work with the number of sg entries dma_map_sg
 * returns, or alternatively stop on the first sg_dma_len(sg) which
 * is 0.
 */
...
#ifdef CONFIG_NEED_SG_DMA_LENGTH
#define sg_dma_len(sg)		((sg)->dma_length)
#else
#define sg_dma_len(sg)		((sg)->length)
#endif


On the other hand, multi_v7_defconfig has CONFIG_NEED_SG_DMA_LENGTH
enabled, so sg_dma_len(sg) defaults to sg->dma_length and it would need
to be used after calling dma_map_sg() (as indicated in the comment from
include/linux/scatterlist.h).


Ovidiu

>  drivers/crypto/allwinner/sun8i-ss/sun8i-ss-cipher.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/crypto/allwinner/sun8i-ss/sun8i-ss-cipher.c b/drivers/crypto/allwinner/sun8i-ss/sun8i-ss-cipher.c
> index 4caf17310e90..ddec1b08d4f6 100644
> --- a/drivers/crypto/allwinner/sun8i-ss/sun8i-ss-cipher.c
> +++ b/drivers/crypto/allwinner/sun8i-ss/sun8i-ss-cipher.c
> @@ -141,7 +141,7 @@ static int sun8i_ss_setup_ivs(struct skcipher_request *areq)
>  
>  	/* we need to copy all IVs from source in case DMA is bi-directionnal */
>  	while (sg && len) {
> -		if (sg_dma_len(sg) == 0) {
> +		if (sg->length == 0) {
>  			sg = sg_next(sg);
>  			continue;
>  		}