Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
References: <alpine.DEB.2.21.1909290010500.2636@nanos.tec.linutronix.de>
 <CAHk-=wgjC01UaoV35PZvGPnrQ812SRGPoV7Xp63BBFxAsJjvrg@mail.gmail.com>
 <20191006114129.GD24605@amd> <CAHk-=wjvhovO6V4-zT=xEMFnRonYteZvsPo-S0_n_DetSTUk5A@mail.gmail.com>
 <20191006173501.GA31243@amd>
In-Reply-To: <20191006173501.GA31243@amd>
From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Sun, 6 Oct 2019 11:06:38 -0700
Message-ID: <CAHk-=whgfz2+OgBTVrHLoHK57emYb4gN6TtJ_s-607U=jBQ+ig@mail.gmail.com>
Subject: Re: x86/random: Speculation to the rescue
To:     Pavel Machek <pavel@ucw.cz>
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        "Ahmed S. Darwish" <darwish.07@gmail.com>,
        LKML <linux-kernel@vger.kernel.org>,
        "Theodore Ts'o" <tytso@mit.edu>,
        Nicholas Mc Guire <hofrat@opentech.at>,
        "the arch/x86 maintainers" <x86@kernel.org>,
        Andy Lutomirski <luto@kernel.org>,
        Kees Cook <keescook@chromium.org>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Sun, Oct 6, 2019 at 10:35 AM Pavel Machek <pavel@ucw.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