linux-kernel - RE: [PATCH v2 4/4] crypto: starfive

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Date:   Thu, 9 Feb 2023 09:33:06 +0000
From:   JiaJie Ho <jiajie.ho@...rfivetech.com>
To:     Herbert Xu <herbert@...dor.apana.org.au>
CC:     "David S . Miller" <davem@...emloft.net>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Emil Renner Berthing <kernel@...il.dk>,
        Conor Dooley <conor.dooley@...rochip.com>,
        "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>
Subject: RE: [PATCH v2 4/4] crypto: starfive - Add hash and HMAC support



> -----Original Message-----
> From: Herbert Xu <herbert@...dor.apana.org.au>
> Sent: 9 February, 2023 5:15 PM
> To: JiaJie Ho <jiajie.ho@...rfivetech.com>
> Cc: David S . Miller <davem@...emloft.net>; Rob Herring
> <robh+dt@...nel.org>; Krzysztof Kozlowski
> <krzysztof.kozlowski+dt@...aro.org>; Emil Renner Berthing
> <kernel@...il.dk>; Conor Dooley <conor.dooley@...rochip.com>; linux-
> crypto@...r.kernel.org; devicetree@...r.kernel.org; linux-
> kernel@...r.kernel.org; linux-riscv@...ts.infradead.org
> Subject: Re: [PATCH v2 4/4] crypto: starfive - Add hash and HMAC support
> 
> On Mon, Jan 30, 2023 at 11:42:42PM +0800, Jia Jie Ho wrote:
> >
> > +	cryp->hash_data = (void *)__get_free_pages(GFP_KERNEL |
> GFP_DMA32,
> > +pages);
> 
> Why do you copy everything before you feed it to the hardware?
> If the issue is alignment then surely you should only to copy a small amount
> of header (and perhaps trailer) for that?
> 

The DMA can only support 32-bit addressing.
So, I am copying everything in case kernel allocated memory region >32-bit for a user app.

> > +static int starfive_hash_export(struct ahash_request *req, void *out)
> > +{
> > +	struct starfive_cryp_request_ctx *rctx = ahash_request_ctx(req);
> > +
> > +	memcpy(out, rctx, sizeof(*rctx));
> > +
> > +	return 0;
> > +}
> 
> You are supposed to extract the entire hardware state after each operation
> and store that in the request context.  Since your request context doesn't
> appear to contain any hash state, this can't possibly work.
> 
> Does your hardware allow the non-finalised hash state to be exported, and
> re-imported later? If not then you can only implement support for digest and
> must use a fallback for everything else.

The hardware doesn't support this. I'll add the fallback in the next version.
Thanks for taking time reviewing this patch series.

Regards,
Jia Jie