Message-ID: <sashiko-outbox-204176@kernel.org>
From: sashiko-bot@kernel.org
Subject: Re: [PATCH RFC] crypto: caam - never share the gcm and skcipher
 descriptors serially
Reply-To: sashiko-reviews@lists.linux.dev
To: "Vincent Jardin" <vjardin@free.fr>, =?utf-8?b?SG9yaWEgR2VhbnTEgw==?= <horia.geanta@nxp.com>, "Pankaj
 Gupta" <pankaj.gupta@nxp.com>, "Sahil Malhotra" <sahil.malhotra@nxp.com>, "Herbert
 Xu" <herbert@gondor.apana.org.au>, "David S. Miller" <davem@davemloft.net>
Cc: linux-crypto@vger.kernel.org
In-Reply-To: <20261109-for-upstream-caam-shdsc-share-never-v1-v1-1-65a1dd146db2@free.fr>
References: <20261109-for-upstream-caam-shdsc-share-never-v1-v1-1-65a1dd146db2@free.fr>
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Date: Sun, 08 Nov 2026 23:55:52 +0000
Precedence: list

Thank you for your contribution! Sashiko AI review found 1 potential
issue to consider:
- [Low] crypto: caam: dead sharing jumps and HDR_SAVECTX with
  HDR_SHARE_NEVER
--

commit 9b09bbe924ba4f39f4ea4b61b1bb908c38315173
Author: Vincent Jardin <vjardin@free.fr>

crypto: caam - never share the gcm and skcipher descriptors serially

This commit changes the GCM and skcipher shared descriptors from
HDR_SHARE_SERIAL to HDR_SHARE_NEVER so jobs using the same key are not
serialized by the SEC hardware.

> diff --git a/drivers/crypto/caam/caamalg_desc.c b/drivers/crypto/caam/caa=
malg_desc.c
> index 04c1105eb1f58..32d614a3431da 100644
> --- a/drivers/crypto/caam/caamalg_desc.c
> +++ b/drivers/crypto/caam/caamalg_desc.c
> @@ -639,7 +639,7 @@ void cnstr_shdsc_gcm_encap(u32 * const desc, struct a=
lginfo *cdata,
>  	u32 *key_jump_cmd, *zero_payload_jump_cmd, *zero_assoc_jump_cmd1,
>  	    *zero_assoc_jump_cmd2;
> =20
> -	init_sh_desc(desc, HDR_SHARE_SERIAL);
> +	init_sh_desc(desc, HDR_SHARE_NEVER);
> =20
>  	/* skip key loading if they are loaded due to sharing */
>  	key_jump_cmd =3D append_jump(desc, JUMP_JSL | JUMP_TEST_ALL |
> @@ -765,7 +765,7 @@ void cnstr_shdsc_gcm_decap(u32 * const desc, struct a=
lginfo *cdata,
>  {
>  	u32 *key_jump_cmd, *zero_payload_jump_cmd, *zero_assoc_jump_cmd1;
> =20
> -	init_sh_desc(desc, HDR_SHARE_SERIAL);
> +	init_sh_desc(desc, HDR_SHARE_NEVER);
> =20
>  	/* skip key loading if they are loaded due to sharing */
>  	key_jump_cmd =3D append_jump(desc, JUMP_JSL |
> @@ -1463,7 +1463,7 @@ void cnstr_shdsc_skcipher_encap(u32 * const desc, s=
truct alginfo *cdata,
>  	bool is_chacha20 =3D ((cdata->algtype & OP_ALG_ALGSEL_MASK) =3D=3D
>  			    OP_ALG_ALGSEL_CHACHA20);
> =20
> -	init_sh_desc(desc, HDR_SHARE_SERIAL | HDR_SAVECTX);
> +	init_sh_desc(desc, HDR_SHARE_NEVER | HDR_SAVECTX);
>  	/* Skip if already shared */
>  	key_jump_cmd =3D append_jump(desc, JUMP_JSL | JUMP_TEST_ALL |
>  				   JUMP_COND_SHRD);
> @@ -1539,7 +1539,7 @@ void cnstr_shdsc_skcipher_decap(u32 * const desc, s=
truct alginfo *cdata,
>  	bool is_chacha20 =3D ((cdata->algtype & OP_ALG_ALGSEL_MASK) =3D=3D
>  			    OP_ALG_ALGSEL_CHACHA20);
> =20
> -	init_sh_desc(desc, HDR_SHARE_SERIAL | HDR_SAVECTX);
> +	init_sh_desc(desc, HDR_SHARE_NEVER | HDR_SAVECTX);
>  	/* Skip if already shared */
>  	key_jump_cmd =3D append_jump(desc, JUMP_JSL | JUMP_TEST_ALL |
>  				   JUMP_COND_SHRD);

[Severity: Low]
With HDR_SHARE_NEVER, should HDR_SAVECTX and the JUMP_COND_SHRD jumps also
be dropped from these four descriptors?

All CAAM job backends defer sharing mode to the shared descriptor header,
so HDR_SHARE_NEVER disables descriptor sharing across jobs and JUMP_COND_SH=
RD
is never true. Keeping key_jump_cmd and the JUMP_COND_SHRD branch in
append_dec_op1() called by cnstr_shdsc_skcipher_decap() leaves unreachable
instructions in the descriptors that waste space and DECO cycles on every
job, and HDR_SAVECTX only applies when a descriptor is self-shared.

--=20
Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20261109-for-upstre=
am-caam-shdsc-share-never-v1-v1-1-65a1dd146db2@free.fr?part=3D1