From: Peter Zijlstra <peterz@infradead.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "Theodore Y. Ts'o" <tytso@mit.edu>,
Thomas Gleixner <tglx@linutronix.de>,
"Ahmed S. Darwish" <darwish.07@gmail.com>,
LKML <linux-kernel@vger.kernel.org>,
Nicholas Mc Guire <hofrat@opentech.at>,
the arch/x86 maintainers <x86@kernel.org>,
Andy Lutomirski <luto@kernel.org>,
Kees Cook <keescook@chromium.org>
Subject: Re: x86/random: Speculation to the rescue
Date: Mon, 30 Sep 2019 18:32:15 +0200 [thread overview]
Message-ID: <20190930163215.GH4519@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <CAHk-=wg7YAx_+CDe6fUqApPD_ghP18H9sPnJWWUg32pQ4pU82g@mail.gmail.com>
On Mon, Sep 30, 2019 at 09:15:55AM -0700, Linus Torvalds wrote:
> On Mon, Sep 30, 2019 at 6:16 AM Theodore Y. Ts'o <tytso@mit.edu> wrote:
> But it _also_ means that if you have a small and excessively stupid
> in-order CPU, I can almost guarantee that you will at least have cache
> misses likely all the way out to memory. So a CPU-only loop like the
> LFSR thing that Thomas reports generates entropy even on its own would
> likely generate nothing at all on a simple in-order core - but I do
In my experience LFSRs are good at defeating branch predictors, which
would make even in-order cores suffer lots of branch misses. And that
might be enough, maybe.
next prev parent reply other threads:[~2019-09-30 16:32 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-28 22:24 x86/random: Speculation to the rescue Thomas Gleixner
2019-09-28 23:53 ` Linus Torvalds
2019-09-29 7:40 ` Thomas Gleixner
2019-09-29 8:05 ` Alexander E. Patrakov
2019-09-30 1:16 ` Linus Torvalds
2019-09-30 2:59 ` Linus Torvalds
2019-09-30 6:10 ` Borislav Petkov
2019-09-30 16:06 ` Linus Torvalds
2019-10-01 13:51 ` Borislav Petkov
2019-10-01 17:14 ` Linus Torvalds
2019-10-01 17:50 ` [PATCH] char/random: Add a newline at the end of the file Borislav Petkov
2019-09-30 18:05 ` x86/random: Speculation to the rescue Kees Cook
2019-09-30 3:37 ` Theodore Y. Ts'o
2019-09-30 13:16 ` Theodore Y. Ts'o
2019-09-30 16:15 ` Linus Torvalds
2019-09-30 16:32 ` Peter Zijlstra [this message]
2019-09-30 17:03 ` Linus Torvalds
2019-10-01 10:28 ` David Laight
2019-10-15 21:50 ` Thomas Gleixner
2019-10-01 16:15 ` Ahmed S. Darwish
2019-10-01 16:37 ` Kees Cook
2019-10-01 17:18 ` Ahmed S. Darwish
2019-10-01 17:25 ` Linus Torvalds
2019-10-06 12:07 ` Pavel Machek
2019-10-02 12:01 ` Theodore Y. Ts'o
2019-10-06 11:41 ` Pavel Machek
2019-10-06 17:26 ` Linus Torvalds
2019-10-06 17:35 ` Pavel Machek
2019-10-06 18:06 ` Linus Torvalds
2019-10-06 18:21 ` Pavel Machek
2019-10-06 18:26 ` Linus Torvalds
2019-10-07 11:47 ` Theodore Y. Ts'o
2019-10-07 22:18 ` Pavel Machek
2019-10-08 11:33 ` David Laight
2019-10-09 8:02 ` Pavel Machek
2019-10-09 9:37 ` David Laight
2019-10-01 2:14 hgntkwis
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