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From:   "Jason A. Donenfeld" <Jason@zx2c4.com>
Date:   Tue, 22 Mar 2022 10:40:43 -0600
Message-ID: <CAHmME9pTX8MK-cJC0zSMU0PBtyE3iTFQTCRoM8RG1zA+fCaTBw@mail.gmail.com>
Subject: Re: [PATCH v1] random: block in /dev/urandom
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     Guenter Roeck <linux@roeck-us.net>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux Crypto Mailing List <linux-crypto@vger.kernel.org>,
        linux-arch <linux-arch@vger.kernel.org>,
        Dinh Nguyen <dinguyen@kernel.org>,
        Nick Hu <nickhu@andestech.com>,
        Max Filippov <jcmvbkbc@gmail.com>,
        Palmer Dabbelt <palmer@dabbelt.com>,
        "David S . Miller" <davem@davemloft.net>,
        Yoshinori Sato <ysato@users.sourceforge.jp>,
        Michal Simek <monstr@monstr.eu>,
        Borislav Petkov <bp@alien8.de>, Guo Ren <guoren@kernel.org>,
        Geert Uytterhoeven <geert@linux-m68k.org>,
        Joshua Kinard <kumba@gentoo.org>,
        David Laight <David.Laight@aculab.com>,
        Dominik Brodowski <linux@dominikbrodowski.net>,
        Eric Biggers <ebiggers@google.com>,
        Ard Biesheuvel <ardb@kernel.org>,
        Arnd Bergmann <arnd@arndb.de>,
        Thomas Gleixner <tglx@linutronix.de>,
        Andy Lutomirski <luto@kernel.org>,
        Kees Cook <keescook@chromium.org>,
        Lennart Poettering <mzxreary@0pointer.de>,
        Konstantin Ryabitsev <konstantin@linuxfoundation.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        "Theodore Ts'o" <tytso@mit.edu>
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Hi Linus,

On Tue, Mar 22, 2022 at 10:27 AM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> On Tue, Mar 22, 2022 at 8:58 AM Guenter Roeck <linux@roeck-us.net> wrote:
> >
> > This patch (or a later version of it) made it into mainline and causes a
> > large number of qemu boot test failures for various architectures (arm,
> > m68k, microblaze, sparc32, xtensa are the ones I observed). Common
> > denominator is that boot hangs at "Saving random seed:". A sample bisect
> > log is attached. Reverting this patch fixes the problem.
>
> Ok, it was worth trying, but yeah, it clearly causes problems for
> various platforms that can't do jitter entropy and have nothing else
> happening either.
>
> Will revert.

Shucks. I wish I had a good argument here, but I suppose the most I
can say is maybe we'll be able to revisit it some time off. I'll send
you the revert patch in a minute.

Jason