linux-kernel - Re: [PATCH crypto-stable] crypto: arch/lib - limit simd usage to PAGE

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Date:   Wed, 22 Apr 2020 01:38:40 -0600
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     Ard Biesheuvel <ardb@...nel.org>
Cc:     Eric Biggers <ebiggers@...nel.org>,
        Sebastian Siewior <bigeasy@...utronix.de>,
        linux-rt-users@...r.kernel.org,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Linux Crypto Mailing List <linux-crypto@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH crypto-stable] crypto: arch/lib - limit simd usage to
 PAGE_SIZE chunks

On Wed, Apr 22, 2020 at 1:23 AM Ard Biesheuvel <ardb@...nel.org> wrote:
> So I think 4 KB is indeed a reasonable quantum of work here. Only
> PAGE_SIZE is not necessarily equal to 4 KB on arm64, so we should use
> SZ_4K instead.

Will wait to hear the rt guys' opinion, but sure, we can do SZ_4K
explicitly. If we go with that in the end, v2 will adjust the other
places that are already using PAGE_SIZE.

> So do we have any callers that are likely to pass more than 4 KB of
> input at a time?

Network packets can be big -- ethernet jumbo packets are 9k, for
example -- so that means this could potentially ipsec, wireguard, and
maybe wifi too. (Crypto api users might go through another layer of
indirection that splits things up smaller, maybe.)