linux-kernel - Re: x86/random: Speculation to the rescue

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Message-ID: <CAHk-=wjvhovO6V4-zT=xEMFnRonYteZvsPo-S0_n_DetSTUk5A@mail.gmail.com>
Date:   Sun, 6 Oct 2019 10:26:18 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Pavel Machek <pavel@....cz>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        "Ahmed S. Darwish" <darwish.07@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        "Theodore Ts'o" <tytso@....edu>,
        Nicholas Mc Guire <hofrat@...ntech.at>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Kees Cook <keescook@...omium.org>
Subject: Re: x86/random: Speculation to the rescue

On Sun, Oct 6, 2019 at 4:41 AM Pavel Machek <pavel@....cz> wrote:
>
> Should we have some kind of notifier chain, so that we could utilize
> better random sources (spinning rust) if we had them?

The spinning rust will get entropy on its own just thanks to the
regular interrupt stuff. And the kernel tryin gto do IO is a bad idea.

Plus I think it's kind of pointless to do anythign at all for things
like spinning rust in this day and age. It's no longer relevant, and
never really was in the area where this was a problem.

Also, I don't really like the notion of random (sic) notifiers that
different drivers or things could attach to this thing. People will
disagree about how much entropy it has anyway, and I'd rather have
_one_ clear implementation that people can look at and comment on and
try to actually write an academic paper on and suggest improvements
to, than some generic "entropy notifier interface" that then gets
whatever input somebody decides is appropriate.

We already have interfaces for "I think I have interesting data":
add_interrupt_randomness(), add_device_randomness(),
add_hwgenerator_randomness() are all for different sources of entropy.

             Linus