linux-kernel - Re: [PATCH v4 03/11] riscv: use fallback for random_get

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Message-ID: <CAHmME9qGzW1+dWLvObjQ4ofGcCU1tOwTB+qJTVs2ufEmAEhbrA@mail.gmail.com>
Date:   Thu, 14 Apr 2022 00:40:19 +0200
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     Rob Herring <robh@...nel.org>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" 
        <linux-crypto@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Arnd Bergmann <arnd@...db.de>, "Theodore Ts'o" <tytso@....edu>,
        Dominik Brodowski <linux@...inikbrodowski.net>,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        "David S . Miller" <davem@...emloft.net>,
        Richard Weinberger <richard@....at>,
        Anton Ivanov <anton.ivanov@...bridgegreys.com>,
        Johannes Berg <johannes@...solutions.net>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H . Peter Anvin" <hpa@...or.com>, Chris Zankel <chris@...kel.net>,
        Max Filippov <jcmvbkbc@...il.com>,
        John Stultz <john.stultz@...aro.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Dinh Nguyen <dinguyen@...nel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-m68k <linux-m68k@...ts.linux-m68k.org>,
        "open list:MIPS" <linux-mips@...r.kernel.org>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        sparclinux <sparclinux@...r.kernel.org>,
        linux-um@...ts.infradead.org, X86 ML <x86@...nel.org>,
        linux-xtensa@...ux-xtensa.org
Subject: Re: [PATCH v4 03/11] riscv: use fallback for random_get_entropy()
 instead of zero

Hi Rob,

On Wed, Apr 13, 2022 at 4:40 PM Rob Herring <robh@...nel.org> wrote:
> Moving this check to get_cycles() implementation would eliminate the
> RiscV implementation of random_get_entropy() if you follow my other
> suggestion.

Not an option. random_get_entropy() != get_cycles(). Sometimes these
are different functions. Returning random_get_entropy_fallback() from
get_cycles(), for example, wouldn't make any sense.

Jason