Re: [PATCH v5] random: remove early archrandom abstraction

[Catalin Marinas]

On Tue, Nov 01, 2022 at 01:25:28PM +0100, Jason A. Donenfeld wrote:
> The arch_get_random*_early() abstraction is not completely useful and
> adds complexity, because it's not a given that there will be no calls to
> arch_get_random*() between random_init_early(), which uses
> arch_get_random*_early(), and init_cpu_features(). During that gap,
> crng_reseed() might be called, which uses arch_get_random*(), since it's
> mostly not init code.
> 
> Instead we can test whether we're in the early phase in
> arch_get_random*() itself, and in doing so avoid all ambiguity about
> where we are. Fortunately, the only architecture that currently
> implements arch_get_random*_early() also has an alternatives-based cpu
> feature system, one flag of which determines whether the other flags
> have been initialized. This makes it possible to do the early check with
> zero cost once the system is initialized.
> 
> Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> Cc: Will Deacon <will@xxxxxxxxxx>
> Cc: Ard Biesheuvel <ardb@xxxxxxxxxx>
> Cc: Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx>
> Signed-off-by: Jason A. Donenfeld <Jason@xxxxxxxxx>

Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx>