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Date: Thu, 22 Aug 2024 09:58:55 +0100
From: Catalin Marinas <catalin.marinas@arm.com>
To: Mark Brown <broonie@kernel.org>
Cc: Will Deacon <will@kernel.org>, Jonathan Corbet <corbet@lwn.net>,
	Andrew Morton <akpm@linux-foundation.org>,
	Marc Zyngier <maz@kernel.org>,
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Subject: Re: [PATCH v11 05/39] arm64: Document boot requirements for Guarded
 Control Stacks
Message-ID: <Zsb9z2giUQbUTH5a@arm.com>
References: <20240822-arm64-gcs-v11-0-41b81947ecb5@kernel.org>
 <20240822-arm64-gcs-v11-5-41b81947ecb5@kernel.org>
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In-Reply-To: <20240822-arm64-gcs-v11-5-41b81947ecb5@kernel.org>

On Thu, Aug 22, 2024 at 02:15:08AM +0100, Mark Brown wrote:
> FEAT_GCS introduces a number of new system registers, we require that
> access to these registers is not trapped when we identify that the feature
> is present.  There is also a HCRX_EL2 control to make GCS operations
> functional.
> 
> Since if GCS is enabled any function call instruction will cause a fault
> we also require that the feature be specifically disabled, existing
> kernels implicitly have this requirement and especially given that the
> MMU must be disabled it is difficult to see a situation where leaving
> GCS enabled would be reasonable.
> 
> Reviewed-by: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
> Signed-off-by: Mark Brown <broonie@kernel.org>

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