[PATCH v2 3/4] arm64/fp: Clarify effect of setting an unsupported system VL

From: Mark Brown
Date: Wed Jan 24 2024 - 13:13:49 EST


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@xxxxxxx>
Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
---
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.

--
2.30.2