linux-kernel - Re: [PATCH 0/5] crypto: caam - avoid allocating memory at crypto request runtime

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Message-ID: <20201203083829.GA20873@gondor.apana.org.au>
Date:   Thu, 3 Dec 2020 19:38:29 +1100
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     "Iuliana Prodan (OSS)" <iuliana.prodan@....nxp.com>,
        "David S. Miller" <davem@...emloft.net>,
        Horia Geanta <horia.geanta@....com>,
        Aymen Sghaier <aymen.sghaier@....com>,
        Silvano Di Ninno <silvano.dininno@....com>,
        Franck Lenormand <franck.lenormand@....com>,
        Linux Crypto Mailing List <linux-crypto@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-imx <linux-imx@....com>,
        Iuliana Prodan <iuliana.prodan@....com>
Subject: Re: [PATCH 0/5] crypto: caam - avoid allocating memory at crypto
 request runtime

On Thu, Dec 03, 2020 at 09:34:08AM +0100, Ard Biesheuvel wrote:
>
> > CRYPTO_ALG_ALLOCATES_MEMORY flag is limited only to
> > dm-crypt use-cases, which seems to be 4 entries maximum.
> > Therefore in reqsize we allocate memory for maximum 4 entries
> > for src and 4 for dst, aligned.
> > If the driver needs more than the 4 entries maximum, the memory
> > is dynamically allocated, at runtime.
> 
> I'm confused. So the driver does allocate memory in some cases, right?
> So why is it justified to remove CRYPTO_ALG_ALLOCATES_MEMORY?

Because it's only required by dm-crypt, we should modify the
semantics for ALLOCATES_MEMORY such that it only includes those
that require allocations even when the SG list is of 4 entries
or less.

We should update the documentation.

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