From: Rik van Riel <riel@redhat.com>
Subject: Re: [kernel-hardening] Re: HalfSipHash Acceptable Usage
Date: Wed, 21 Dec 2016 11:41:28 -0500
Message-ID: <1482338488.11006.70.camel@redhat.com>
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On Wed, 2016-12-21 at 10:55 -0500, George Spelvin wrote:
> Actually, DJB just made a very relevant suggestion.
>=20
> As I've mentioned, the 32-bit performance problems are an x86-
> specific
> problem.=C2=A0=C2=A0ARM does very well, and other processors aren't bad a=
t all.
>=20
> SipHash fits very nicely (and runs very fast) in the MMX registers.
>=20
> They're 64 bits, and there are 8 of them, so the integer registers
> can
> be reserved for pointers and loop counters and all that.=C2=A0=C2=A0And t=
here's
> reference code available.
>=20
> How much does kernel_fpu_begin()/kernel_fpu_end() cost?

Those can be very expensive. Almost certainly not
worth it for small amounts of data.

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