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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>,
        Marc Zyngier <maz@kernel.org>
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        "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" 
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From:   Richard Henderson <richard.henderson@linaro.org>
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Date:   Fri, 8 Nov 2019 15:52:09 +0100
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On 11/8/19 3:24 PM, Ard Biesheuvel wrote:
>>> To add_interrupt_randomness(), invoked by handle_irq_event_percpu().
>>> Better if I reword the above to include the function name?
>>>
>>
>> This is one of the several places where arch_random_get_seed_long() is
>> called, so if you are going to single it out like that, it does make
>> sense to clarify that.
>>
> 
> Looking more carefully at that code, it seems we call
> arch_get_random_seed_long() NR_CPUS times per second, and assuming
> that our RNDRRS sysreg will be reseeded from a resource that is shared
> between all the cores, I am now wondering if this is such a good fit
> after all, especially in the context of virtualization and
> accessibility of both sysregs all the way down to EL0.
> 
> I propose we go with RNDR instead, at least for the time being, and
> once actual hardware appears, we can try to figure out how these
> pieces best fit together.

This is what I started with, based on the powerpc implementation.
I can certainly revert to that easily.


r~