Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <CAHmME9qTA90=GEr6h1GZh0CjS+6tpe5uuqkYoJVv79h0zd0w1w@mail.gmail.com>
 <20220719130207.147536-1-Jason@zx2c4.com> <Yt5gBZe9F1BE0MVF@zn.tnic>
 <Yt5hwxC1xgvA8Asw@zx2c4.com> <10561a841a7342c882aabb0fbdbfc762@AcuMS.aculab.com>
In-Reply-To: <10561a841a7342c882aabb0fbdbfc762@AcuMS.aculab.com>
From:   "Jason A. Donenfeld" <Jason@zx2c4.com>
Date:   Mon, 25 Jul 2022 11:37:23 +0200
Message-ID: <CAHmME9p_9j_B2d1h3cKVbv=ucNAa9_grBBW_jdWa8GTbm5WpZg@mail.gmail.com>
Subject: Re: [PATCH v3] random: handle archrandom with multiple longs
To:     David Laight <David.Laight@aculab.com>
Cc:     Borislav Petkov <bp@suse.de>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>,
        "linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
        "linux-s390@vger.kernel.org" <linux-s390@vger.kernel.org>,
        "x86@kernel.org" <x86@kernel.org>, Will Deacon <will@kernel.org>,
        Alexander Gordeev <agordeev@linux.ibm.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        "H . Peter Anvin" <hpa@zytor.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Heiko Carstens <hca@linux.ibm.com>,
        Johannes Berg <johannes@sipsolutions.net>,
        Mark Rutland <mark.rutland@arm.com>,
        Harald Freudenberger <freude@linux.ibm.com>,
        Michael Ellerman <mpe@ellerman.id.au>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Mon, Jul 25, 2022 at 11:36 AM David Laight <David.Laight@aculab.com> wrote:
>
> ...
> > More directly, the reason we don't want to error is because the use case
> > has fallbacks meant to handle errors. The cascade looks like this
> > (quoting from the other email):
> >
> >     unsigned long array[whatever];
> >     for (i = 0; i < ARRAY_SIZE(array);) {
> >         longs = arch_get_random_seed_longs(&array[i], ARRAY_SIZE(array) - i);
> >         if (longs) {
> >             i += longs;
> >             continue;
> >         }
> >         longs = arch_get_random_longs(&array[i], ARRAY_SIZE(array) - i);
> >         if (longs) {
> >             i += longs;
> >             continue;
> >         }
> >         array[i++] = random_get_entropy();
> >     }
> >
> > It tries to get the best that it can as much as it can, but isn't going
> > to block or do anything too nuts for that.
>
> Do you really want to retry the earlier calls that returned no data?

Does the above code do that?