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Date:   Wed, 23 Mar 2022 07:23:56 -0700
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To:     Mark Brown <broonie@kernel.org>
Cc:     "Jason A. Donenfeld" <Jason@zx2c4.com>,
        linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org,
        linux-arch@vger.kernel.org, Dinh Nguyen <dinguyen@kernel.org>,
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        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>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Theodore Ts'o <tytso@mit.edu>
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From:   Guenter Roeck <linux@roeck-us.net>
Subject: Re: [PATCH v1] random: block in /dev/urandom
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On 3/23/22 05:10, Mark Brown wrote:
> On Tue, Mar 22, 2022 at 02:54:20PM -0700, Guenter Roeck wrote:
>> On 3/22/22 11:24, Mark Brown wrote:
> 
>>> Just as a datapoint for debugging at least qemu/arm is getting coverage
>>> in CI systems (KernelCI is covering a bunch of different emulated
>>> machines and LKFT has at least one configuration as well, clang's tests
>>> have some wider architecture coverage as well I think) and they don't
>>> seem to be seeing any problems - there's some other variable in there.
> 
>> I use buildroot 2021.02.3. I have not changed the buildroot code, and it
>> still seems to be the same in 2022.02. I don't see the problem with all
>> boot tests, only with the architectures mentioned above, and not with all
>> qemu machines on the affected platforms. For arm, mostly older machines
>> are affected (versatile, realview, pxa configurations, collie, integratorcp,
>> sx1, mps2-an385, vexpress-a9, cubieboard). I didn't check, but maybe
>> kernelci doesn't test those machines ?
> 
> Kind of academic given that Jason seems to have a handle on what the
> issues are but for KernelCI it's variations on mach-virt, plus
> versatile-pb.  There's a physical cubietruck as well, and BeagleBone
> Blacks among others.  My best guess would be systems with low RAM are
> somehow more prone to issues.

I don't think it is entirely academic. versatile-pb fails for me;
if it doesn't fail at KernelCI, I'd like to understand why - not to
fix it in my test environment, but to make sure that I _don't_ fix it.
After all, it _is_ a regression. Even if that regression is triggered
by bad (for a given definition of "bad") userspace code, it is still
a regression.

Thanks,
Guenter