linux-kernel - Re: [PATCH 3/4 v3] crypto: octeontx2: Fix address alignment on CN10K A0/A1 and OcteonTX2

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Message-ID: <aC2406qOlaI17_f3@gondor.apana.org.au>
Date: Wed, 21 May 2025 19:28:19 +0800
From: Herbert Xu <herbert@...dor.apana.org.au>
To: Bharat Bhushan <bbhushan2@...vell.com>
Cc: bbrezillon@...nel.org, schalla@...vell.com, davem@...emloft.net,
	giovanni.cabiddu@...el.com, linux@...blig.org,
	bharatb.linux@...il.com, linux-crypto@...r.kernel.org,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH 3/4 v3] crypto: octeontx2: Fix address alignment on CN10K
 A0/A1 and OcteonTX2

On Wed, May 21, 2025 at 03:34:46PM +0530, Bharat Bhushan wrote:
>
> @@ -429,22 +431,51 @@ otx2_sg_info_create(struct pci_dev *pdev, struct otx2_cpt_req_info *req,
>  		return NULL;
>  	}
>  
> -	g_sz_bytes = ((req->in_cnt + 3) / 4) *
> -		      sizeof(struct otx2_cpt_sglist_component);
> -	s_sz_bytes = ((req->out_cnt + 3) / 4) *
> -		      sizeof(struct otx2_cpt_sglist_component);
> +	/* Allocate memory to meet below alignment requirement:
> +	 *  ----------------------------------
> +	 * |    struct otx2_cpt_inst_info     |
> +	 * |    (No alignment required)       |
> +	 * |     -----------------------------|
> +	 * |    | padding for 8B alignment    |
> +	 * |----------------------------------|

This should be updated to show that everything following this
is on an 128-byte boundary.

> +	 * |    SG List Gather/Input memory   |
> +	 * |    Length = multiple of 32Bytes  |
> +	 * |    Alignment = 8Byte             |
> +	 * |----------------------------------|
> +	 * |    SG List Scatter/Output memory |
> +	 * |    Length = multiple of 32Bytes  |
> +	 * |    Alignment = 8Byte             |
> +	 * |    (padding for below alignment) |
> +	 * |     -----------------------------|
> +	 * |    | padding for 32B alignment   |
> +	 * |----------------------------------|
> +	 * |    Result response memory        |
> +	 *  ----------------------------------
> +	 */
>  
> -	dlen = g_sz_bytes + s_sz_bytes + SG_LIST_HDR_SIZE;
> -	align_dlen = ALIGN(dlen, align);
> -	info_len = ALIGN(sizeof(*info), align);
> -	total_mem_len = align_dlen + info_len + sizeof(union otx2_cpt_res_s);
> +	info_len = sizeof(*info);
> +
> +	g_len = ((req->in_cnt + 3) / 4) *
> +		 sizeof(struct otx2_cpt_sglist_component);
> +	s_len = ((req->out_cnt + 3) / 4) *
> +		 sizeof(struct otx2_cpt_sglist_component);
> +
> +	dlen = g_len + s_len + SG_LIST_HDR_SIZE;
> +
> +	/* Allocate extra memory for SG and response address alignment */
> +	total_mem_len = ALIGN(info_len, ARCH_DMA_MINALIGN) + dlen;
> +	total_mem_len = ALIGN(total_mem_len, OTX2_CPT_DPTR_RPTR_ALIGN);
> +	total_mem_len += (OTX2_CPT_RES_ADDR_ALIGN - 1) &
> +			  ~(OTX2_CPT_DPTR_RPTR_ALIGN - 1);
> +	total_mem_len += sizeof(union otx2_cpt_res_s);

This calculation is wrong again.  It should be:

	total_mem_len = ALIGN(info_len, OTX2_CPT_DPTR_RPTR_ALIGN);
	total_mem_len += (ARCH_DMA_MINALIGN - 1) &
			 ~(OTX2_CPT_DPTR_RPTR_ALIGN - 1);
	total_mem_len += ALIGN(dlen, OTX2_CPT_RES_ADDR_ALIGN);
	total_mem_len += sizeof(union otx2_cpt_res_s);

Remember ALIGN may not actually give you extra memory.  So if you
need to add memory for alignment padding, you will need to do it
by hand.

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