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From: Catalin Marinas <catalin.marinas@arm.com>
To: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, Will Deacon <will@kernel.org>,
	Ard Biesheuvel <ardb@kernel.org>,
	Jean-Philippe Brucker <jean-philippe@linaro.org>
Subject: Re: [PATCH v5] random: remove early archrandom abstraction
Date: Tue, 1 Nov 2022 14:05:51 +0000	[thread overview]
Message-ID: <Y2Env04RIXEpNstS@arm.com> (raw)
In-Reply-To: <20221101122527.323843-1-Jason@zx2c4.com>

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@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Ard Biesheuvel <ardb@kernel.org>
> Cc: Jean-Philippe Brucker <jean-philippe@linaro.org>
> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

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

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WARNING: multiple messages have this Message-ID (diff)
From: Catalin Marinas <catalin.marinas@arm.com>
To: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, Will Deacon <will@kernel.org>,
	Ard Biesheuvel <ardb@kernel.org>,
	Jean-Philippe Brucker <jean-philippe@linaro.org>
Subject: Re: [PATCH v5] random: remove early archrandom abstraction
Date: Tue, 1 Nov 2022 14:05:51 +0000	[thread overview]
Message-ID: <Y2Env04RIXEpNstS@arm.com> (raw)
In-Reply-To: <20221101122527.323843-1-Jason@zx2c4.com>

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@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Ard Biesheuvel <ardb@kernel.org>
> Cc: Jean-Philippe Brucker <jean-philippe@linaro.org>
> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

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

  parent reply	other threads:[~2022-11-01 14:06 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-10-28 23:40 [PATCH] random: remove early archrandom abstraction Jason A. Donenfeld
2022-10-28 23:40 ` Jason A. Donenfeld
2022-10-30 17:30 ` Catalin Marinas
2022-10-30 17:30   ` Catalin Marinas
2022-10-30 21:07   ` Jason A. Donenfeld
2022-10-30 21:07     ` Jason A. Donenfeld
2022-10-30 21:21     ` [PATCH v2] " Jason A. Donenfeld
2022-10-30 21:21       ` Jason A. Donenfeld
2022-10-31 10:28       ` [PATCH v3] " Jason A. Donenfeld
2022-10-31 10:28         ` Jason A. Donenfeld
2022-11-01 11:39         ` Catalin Marinas
2022-11-01 11:39           ` Catalin Marinas
2022-11-01 11:54           ` Jason A. Donenfeld
2022-11-01 11:54             ` Jason A. Donenfeld
2022-11-01 11:56             ` [PATCH v4] " Jason A. Donenfeld
2022-11-01 11:56               ` Jason A. Donenfeld
2022-11-01 12:25               ` [PATCH v5] " Jason A. Donenfeld
2022-11-01 12:25                 ` Jason A. Donenfeld
2022-11-01 12:36                 ` Mark Rutland
2022-11-01 12:36                   ` Mark Rutland
2022-11-01 13:02                   ` Jason A. Donenfeld
2022-11-01 13:02                     ` Jason A. Donenfeld
2022-11-01 13:07                     ` Mark Rutland
2022-11-01 13:07                       ` Mark Rutland
2022-11-01 14:05                 ` Catalin Marinas [this message]
2022-11-01 14:05                   ` Catalin Marinas

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