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

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Message-ID: <20190530132623.4h3y2bymv4uvfnms@gondor.apana.org.au>
Date:   Thu, 30 May 2019 21:26:23 +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 Thu, May 30, 2019 at 01:18:34PM +0000, Horia Geanta wrote:
>
> I guess there are only two options:
> -either cache line sharing is avoided OR
> -users need to be *aware* they are sharing the cache line and some rules /
> assumptions are in place on how to safely work on the data

No there is a third option and it's very simple:

You must only access the virtual addresses given to you before DMA
mapping or after DMA unmapping.

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