linux-kernel - Re: [PATCH 1/4] crypto: nintendo-aes

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Date:   Wed, 22 Sep 2021 08:04:39 +0200
From:   Corentin Labbe <clabbe.montjoie@...il.com>
To:     Emmanuel Gil Peyrot <linkmauve@...kmauve.fr>
Cc:     linux-crypto@...r.kernel.org, Ash Logan <ash@...quark.com>,
        Jonathan Neuschäfer <j.ne@...teo.net>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Rob Herring <robh+dt@...nel.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH 1/4] crypto: nintendo-aes - add a new AES driver

Le Tue, Sep 21, 2021 at 11:39:27PM +0200, Emmanuel Gil Peyrot a écrit :
> This engine implements AES in CBC mode, using 128-bit keys only.  It is
> present on both the Wii and the Wii U, and is apparently identical in
> both consoles.
> 
> The hardware is capable of firing an interrupt when the operation is
> done, but this driver currently uses a busy loop, I’m not too sure
> whether it would be preferable to switch, nor how to achieve that.
> 
> It also supports a mode where no operation is done, and thus could be
> used as a DMA copy engine, but I don’t know how to expose that to the
> kernel or whether it would even be useful.
> 
> In my testing, on a Wii U, this driver reaches 80.7 MiB/s, while the
> aes-generic driver only reaches 30.9 MiB/s, so it is a quite welcome
> speedup.
> 
> This driver was written based on reversed documentation, see:
> https://wiibrew.org/wiki/Hardware/AES
> 
> Signed-off-by: Emmanuel Gil Peyrot <linkmauve@...kmauve.fr>
> Tested-by: Emmanuel Gil Peyrot <linkmauve@...kmauve.fr>  # on Wii U

[...]

> +static int
> +do_crypt(const void *src, void *dst, u32 len, u32 flags)
> +{
> +	u32 blocks = ((len >> 4) - 1) & AES_CTRL_BLOCK;
> +	u32 status;
> +	u32 counter = OP_TIMEOUT;
> +	u32 i;
> +
> +	/* Flush out all of src, we can’t know whether any of it is in cache */
> +	for (i = 0; i < len; i += 32)
> +		__asm__("dcbf 0, %0" : : "r" (src + i));
> +	__asm__("sync" : : : "memory");
> +
> +	/* Set the addresses for DMA */
> +	iowrite32be(virt_to_phys((void *)src), base + AES_SRC);
> +	iowrite32be(virt_to_phys(dst), base + AES_DEST);

Hello

Since you do DMA operation, I think you should use the DMA-API and call dma_map_xxx()
This will prevent the use of __asm__ and virt_to_phys().

Regards