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

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Date:   Sun, 6 Oct 2019 11:06:38 -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 10:35 AM Pavel Machek <pavel@....cz> wrote:
>
> It will not: boot is now halted because systemd wants some
> entropy. Everything is idle and very little interrupts are
> happening. We have spinning rust, but it is idle, and thus not
> generating any interrupts.

Yes, but we have that problem now solved.

Except on embedded platforms that have garbage CPU's without even a
cycle counter.

But those won't have spinning rust anyway.

Yes, bad SSD's and MMC disks (that they do have) will generate timing
noise too, but in the absense of a cycle counter, that noise won't be
much use.

                 Linus