| Message ID | 20240122-arm64-sve-sme-doc-v1-3-3d492e45265b@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64/fp: Documentation cleanups and clarifications | expand |
On Mon, Jan 22, 2024 at 08:41:53PM +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..ba0a5e5b2523 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 prctl(). Do parallel changes need to be made in sve.rst? (There seems to be so much duplication and copy-paste between these files that I wonder whether it would make sense to merge them... but that's probably a separate discussion.) Nit: is it better to name the prctl here than just to say prctl()? That would be easier for the reader to cross-reference. > > 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..b923727ff4b9 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 prctl(). Ditto. [...] Cheers ---Dave
On Tue, Jan 23, 2024 at 03:49:27PM +0000, Dave Martin wrote: > On Mon, Jan 22, 2024 at 08:41:53PM +0000, Mark Brown wrote: > > /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 prctl(). > Do parallel changes need to be made in sve.rst? They are, in this very patch? > (There seems to be so much duplication and copy-paste between these > files that I wonder whether it would make sense to merge them... but > that's probably a separate discussion.) Indeed, thanks for volunteering. Note that there are differences resulting from specification differences. > Nit: is it better to name the prctl here than just to say prctl()? > That would be easier for the reader to cross-reference. I guess, though it doesn't seem entirely idiomatic.
On Tue, Jan 23, 2024 at 06:42:03PM +0000, Mark Brown wrote: > On Tue, Jan 23, 2024 at 03:49:27PM +0000, Dave Martin wrote: > > On Mon, Jan 22, 2024 at 08:41:53PM +0000, Mark Brown wrote: > > > > /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 prctl(). > > > Do parallel changes need to be made in sve.rst? > > They are, in this very patch? Duh, yes. My brain seems to have auto-ignored the second hunk, since it was clearly a duplicate :P > > (There seems to be so much duplication and copy-paste between these > > files that I wonder whether it would make sense to merge them... but > > that's probably a separate discussion.) > > Indeed, thanks for volunteering. Note that there are differences > resulting from specification differences. Thanks for agreeing to an unspecfied deadline ;) I might have a go at some point though, just to familiarise myself with the differences... > > Nit: is it better to name the prctl here than just to say prctl()? > > That would be easier for the reader to cross-reference. > > I guess, though it doesn't seem entirely idiomatic. I expect counterexamples can be found, but I guess the reader can figure it out either way. Cheers ---Dave
diff --git a/Documentation/arch/arm64/sme.rst b/Documentation/arch/arm64/sme.rst index 3133d0e91b48..ba0a5e5b2523 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 prctl(). 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..b923727ff4b9 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 prctl(). The result can be determined by reopening the file and reading its contents.
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(-)