[v2,3/4] arm64/fp: Clarify effect of setting an unsupported system VL
Commit Message
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(-)
Comments
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
@@ -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.
@@ -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.