linux-kernel - Re: [PATCH] crypto: gcm

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Message-ID: <20190531054250.p2bc3igiu4s7dmvk@gondor.apana.org.au>
Date:   Fri, 31 May 2019 13:42:50 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Horia Geanta <horia.geanta@....com>
Cc:     Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Eric Biggers <ebiggers@...nel.org>,
        Iuliana Prodan <iuliana.prodan@....com>,
        "David S. Miller" <davem@...emloft.net>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>
Subject: Re: [PATCH] crypto: gcm - fix cacheline sharing

On Fri, May 31, 2019 at 05:22:50AM +0000, Horia Geanta wrote:
>
> Unless it's clearly defined *which* virtual addresses mustn't be accessed,
> things won't work properly.
> In theory, any two objects could share a cache line. We can't just stop all
> memory accesses from CPU while a peripheral is busy.

The user obviously can't touch the memory areas potentially under
DMA.  But in this case it's not the user that's doing it, it's
the driver.

So the driver must not touch any virtual pointers given to it
as input/output while the DMA areas are mapped.

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