linux-kernel - Re: [RFCv3 05/15] tcp: authopt: Add crypto initialization

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Date:   Wed, 25 Aug 2021 07:55:49 -0700
From:   Eric Dumazet <edumazet@...gle.com>
To:     Herbert Xu <herbert@...dor.apana.org.au>
Cc:     Eric Dumazet <eric.dumazet@...il.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Eric Biggers <ebiggers@...nel.org>,
        Leonard Crestez <cdleonard@...il.com>,
        Dmitry Safonov <0x7f454c46@...il.com>,
        David Ahern <dsahern@...nel.org>,
        Shuah Khan <shuah@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Kuniyuki Iwashima <kuniyu@...zon.co.jp>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Jakub Kicinski <kuba@...nel.org>,
        Yuchung Cheng <ycheng@...gle.com>,
        Francesco Ruggeri <fruggeri@...sta.com>,
        Mat Martineau <mathew.j.martineau@...ux.intel.com>,
        Christoph Paasch <cpaasch@...le.com>,
        Ivan Delalande <colona@...sta.com>,
        Priyaranjan Jha <priyarjha@...gle.com>,
        Menglong Dong <dong.menglong@....com.cn>,
        netdev <netdev@...r.kernel.org>,
        "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" 
        <linux-crypto@...r.kernel.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFCv3 05/15] tcp: authopt: Add crypto initialization

On Wed, Aug 25, 2021 at 1:08 AM Herbert Xu <herbert@...dor.apana.org.au> wrote:
>
> On Tue, Aug 24, 2021 at 04:34:58PM -0700, Eric Dumazet wrote:
> >
> > On 8/24/21 2:34 PM, Leonard Crestez wrote:
> > > The crypto_shash API is used in order to compute packet signatures. The
> > > API comes with several unfortunate limitations:
> > >
> > > 1) Allocating a crypto_shash can sleep and must be done in user context.
> > > 2) Packet signatures must be computed in softirq context
> > > 3) Packet signatures use dynamic "traffic keys" which require exclusive
> > > access to crypto_shash for crypto_setkey.
> > >
> > > The solution is to allocate one crypto_shash for each possible cpu for
> > > each algorithm at setsockopt time. The per-cpu tfm is then borrowed from
> > > softirq context, signatures are computed and the tfm is returned.
> > >
> >
> > I could not see the per-cpu stuff that you mention in the changelog.
>
> Perhaps it's time we moved the key information from the tfm into
> the request structure for hashes? Or at least provide a way for
> the key to be in the request structure in addition to the tfm as
> the tfm model still works for IPsec.  Ard/Eric, what do you think
> about that?

What is the typical size of a ' tfm' and associated data ?

per-cpu tfm might still make sense, if we had proper NUMA affinities.
AFAIK, currently we can not provide a numa node to crypto allocations.

So using construct like this ends up allocating all data on one single NUMA node

for_each_possible_cpu(cpu) {
    tfm = crypto_alloc_shash(algo->name, 0, 0);
    if (IS_ERR(tfm))
        return PTR_ERR(tfm);
    p_tfm = per_cpu_ptr(algo->tfms, cpu);
    *p_tfm = tfm;
}