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Date: Thu, 25 Jan 2024 13:47:30 +0000
From: Dave Martin <Dave.Martin@arm.com>
To: Mark Brown <broonie@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>, Jonathan Corbet <corbet@lwn.net>,
	linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	Edmund Grimley-Evans <edmund.grimley-evans@arm.com>
Subject: Re: [PATCH v2 3/4] arm64/fp: Clarify effect of setting an
 unsupported system VL
Message-ID: <ZbJmcj0A32+aJIMx@e133380.arm.com>
References: <20240124-arm64-sve-sme-doc-v2-0-fe3964fb3c19@kernel.org>
 <20240124-arm64-sve-sme-doc-v2-3-fe3964fb3c19@kernel.org>
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In-Reply-To: <20240124-arm64-sve-sme-doc-v2-3-fe3964fb3c19@kernel.org>

On Wed, Jan 24, 2024 at 06:12:37PM +0000, Mark Brown wrote:
> The documentation for system vector length configuration does not cover all
> cases where unsupported values are written, tighten it up.
> 
> Reported-by: Edmund Grimley-Evans <edmund.grimley-evans@arm.com>
> Signed-off-by: Mark Brown <broonie@kernel.org>
> ---
>  Documentation/arch/arm64/sme.rst | 5 ++---
>  Documentation/arch/arm64/sve.rst | 5 ++---
>  2 files changed, 4 insertions(+), 6 deletions(-)
> 
> diff --git a/Documentation/arch/arm64/sme.rst b/Documentation/arch/arm64/sme.rst
> index 3133d0e91b48..f4376c06f447 100644
> --- a/Documentation/arch/arm64/sme.rst
> +++ b/Documentation/arch/arm64/sme.rst
> @@ -379,9 +379,8 @@ The regset data starts with struct user_za_header, containing:
>  /proc/sys/abi/sme_default_vector_length
>  
>      Writing the text representation of an integer to this file sets the system
> -    default vector length to the specified value, unless the value is greater
> -    than the maximum vector length supported by the system in which case the
> -    default vector length is set to that maximum.
> +    default vector length to the specified value rounded to a supported value
> +    using the same rules as for setting vector length via PR_SME_SET_VL.
>  
>      The result can be determined by reopening the file and reading its
>      contents.
> diff --git a/Documentation/arch/arm64/sve.rst b/Documentation/arch/arm64/sve.rst
> index b45a2da19bf1..8d8837fc39ec 100644
> --- a/Documentation/arch/arm64/sve.rst
> +++ b/Documentation/arch/arm64/sve.rst
> @@ -423,9 +423,8 @@ The regset data starts with struct user_sve_header, containing:
>  /proc/sys/abi/sve_default_vector_length
>  
>      Writing the text representation of an integer to this file sets the system
> -    default vector length to the specified value, unless the value is greater
> -    than the maximum vector length supported by the system in which case the
> -    default vector length is set to that maximum.
> +    default vector length to the specified value rounded to a supported value
> +    using the same rules as for setting vector length via PR_SVE_SET_VL.
>  
>      The result can be determined by reopening the file and reading its
>      contents.

Since you picked up my suggestion, I guess I owe you a

Reviewed-by: Dave Martin <Dave.Martin@arm.com>

Cheers
---Dave