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Subject: Re: [PATCH v4 1/1] arm64: Implement archrandom.h for ARMv8.5-RNG
To:     Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc:     linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" 
        <linux-crypto@vger.kernel.org>, Mark Rutland <mark.rutland@arm.com>
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 <CAKv+Gu8pb5pBFBg0wGoORmaS6yzmoX7L45LLnhuZhqw4JX7d+w@mail.gmail.com>
From:   Richard Henderson <richard.henderson@linaro.org>
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Date:   Fri, 8 Nov 2019 12:09:57 +0100
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On 11/6/19 10:30 PM, Ard Biesheuvel wrote:
> On Wed, 6 Nov 2019 at 15:20, Richard Henderson
> <richard.henderson@linaro.org> wrote:
>> +static inline bool has_random(void)
>> +{
>> +       /*
>> +        * We "have" RNG if either
>> +        * (1) every cpu in the system has RNG, or
>> +        * (2) in a non-preemptable context, current cpu has RNG.
>> +        * Case 1 is the expected case when RNG is deployed, but
>> +        * case 2 is present as a backup in case some big/little
>> +        * system only has RNG on big cpus, we can still add entropy
>> +        * from the interrupt handler of the big cpus.
> 
> I don't understand the reference to the interrupt handler here.

To add_interrupt_randomness(), invoked by handle_irq_event_percpu().
Better if I reword the above to include the function name?

> It is
> worth mentioning though that this arrangement permits
> rand_initialize() to use the instructions regardless of whether they
> are implemented only by the boot CPU or by all of them.

Yes, I'll include that.


r~