linux-kernel - Re: [PATCH 0/3] random: add random.rng

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Message-ID: <7882e5d2-dd4d-cdfb-2aab-9a3d910882d4@android.com>
Date:   Fri, 14 Feb 2020 10:31:18 -0800
From:   Mark Salyzyn <salyzyn@...roid.com>
To:     Rob Herring <robh@...nel.org>
Cc:     Masami Hiramatsu <mhiramat@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Android Kernel Team <kernel-team@...roid.com>,
        Theodore Ts'o <tytso@....edu>, Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Richard Henderson <richard.henderson@...aro.org>,
        Mark Brown <broonie@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Arvind Sankar <nivedita@...m.mit.edu>,
        Dominik Brodowski <linux@...inikbrodowski.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Alexander Potapenko <glider@...gle.com>,
        Jonathan Corbet <corbet@....net>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Juergen Gross <jgross@...e.com>,
        Linux Doc Mailing List <linux-doc@...r.kernel.org>
Subject: Re: [PATCH 0/3] random: add random.rng_seed to bootconfig entry

On 2/14/20 10:14 AM, Rob Herring wrote:
> On Fri, Feb 14, 2020 at 11:00 AM Mark Salyzyn <salyzyn@...roid.com> wrote:
>> On 2/14/20 5:49 AM, Rob Herring wrote:
>>> On Fri, Feb 14, 2020 at 12:10 AM Masami Hiramatsu <mhiramat@...nel.org> wrote:
>>>> Hi,
>>>>
>>>> The following series is bootconfig based implementation of
>>>> the rng_seed option patch originally from Mark Salyzyn.
>>>> Note that I removed unrelated command line fixes from this
>>>> series.
>>> Why do we need this? There's already multiple other ways to pass
>>> random seed and this doesn't pass the "too complex for the command
>>> line" argument you had for needing bootconfig.
>>>
>>> Rob
>> Android is the use case I can vouch for. But also KVM.
. . .
> I'm familiar with Cuttlefish somewhat. Guess who got virtio-gpu
> working on Android[1]. :) I assume DT doesn't work for you because you
> need x86 builds, but doesn't QEMU use UEFI in that case which also has
> a mechanism for passing entropy.
IDK, will have to ask the Cuttlefish Team why UEFI not being used, will 
get back to you.
>
> To clarify my question: Why do we need random seed in bootconfig
> rather than just the kernel command line? I'm not understanding why
> things changed from your original patch.

Command line was identified as the simplest for them to implement 
generically for the x86 and arm64 Cuttlefish instances and hence my 
original patch series.

However, it also is limited in the size of the entropy string that can 
be provided, so we flipped a coin and decided to accept the bootconfig 
mechanism as a viable alternative; that BTW appeared to be simpler to 
implement (mainly because rubbing out the entropy command line argument 
is not easy).

-- Mark