linux-kernel - Re: [PATCH v4] poly1305: generic C can be faster on chips with slow unaligned access

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Date:   Tue, 08 Nov 2016 08:52:39 +0100
From:   Martin Willi <martin@...ongswan.org>
To:     "Jason A. Donenfeld" <Jason@...c4.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
        Eric Biggers <ebiggers@...gle.com>,
        René van Dorst <opensource@...rst.com>
Subject: Re: [PATCH v4] poly1305: generic C can be faster on chips with slow
 unaligned access


> By using the unaligned access helpers, we drastically improve
> performance on small MIPS routers that have to go through the
> exception fix-up handler for these unaligned accesses.

I couldn't measure any slowdown here, so:

Acked-by: Martin Willi <martin@...ongswan.org>

> -       dctx->s[0] = le32_to_cpuvp(key +  0);
> +       dctx->s[0] = get_unaligned_le32(key +  0);

Not sure what the exact alignment rules for key/iv are, but maybe we
want to replace the same function in chacha20_generic.c as well?

Martin