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2024-11-12arm64/ptrace: Clarify documentation of VL configuration via ptraceMark Brown1-0/+4
When we configure SVE, SSVE or ZA via ptrace we allow the user to configure the vector length and specify any of the flags that are accepted when configuring via prctl(). This includes the S[VM]E_SET_VL_ONEXEC flag which defers the configuration of the VL until an exec(). We don't do anything to limit the provision of register data as part of configuring the _ONEXEC VL but as a function of the VL enumeration support we do this will be interpreted using the vector length currently configured for the process. This is all a bit surprising, and probably we should just not have allowed register data to be specified with _ONEXEC, but it's our ABI so let's add some explicit documentation in both the ABI documents and the source calling out what happens. The comments are also missing the fact that since SME does not have a mandatory 128 bit VL it is possible for VL enumeration to result in the configuration of a higher VL than was requested, cover that too. Signed-off-by: Mark Brown <broonie@kernel.org> Link: https://lore.kernel.org/r/20241106-arm64-sve-ptrace-vl-set-v1-1-3b164e8b559c@kernel.org Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2024-02-21arm64/fp: Clarify effect of setting an unsupported system VLMark Brown1-3/+2
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> Reviewed-by: Dave Martin <Dave.Martin@arm.com> Link: https://lore.kernel.org/r/20240124-arm64-sve-sme-doc-v2-3-fe3964fb3c19@kernel.org Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2024-02-21arm64/sve: Remove bitrotted comment about syscall behaviourMark Brown1-5/+0
When we documented that we always clear state not shared with FPSIMD we didn't catch all of the places that mentioned that state might not be cleared, remove a lingering reference. Reported-by: Edmund Grimley-Evans <edmund.grimley-evans@arm.com> Reviewed-by: Dave Martin <Dave.Martin@arm.com> Signed-off-by: Mark Brown <broonie@kernel.org> Link: https://lore.kernel.org/r/20240124-arm64-sve-sme-doc-v2-1-fe3964fb3c19@kernel.org Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2023-06-21docs: arm64: Move arm64 documentation under Documentation/arch/Jonathan Corbet1-0/+616
Architecture-specific documentation is being moved into Documentation/arch/ as a way of cleaning up the top-level documentation directory and making the docs hierarchy more closely match the source hierarchy. Move Documentation/arm64 into arch/ (along with the Chinese equvalent translations) and fix up documentation references. Cc: Will Deacon <will@kernel.org> Cc: Alex Shi <alexs@kernel.org> Cc: Hu Haowen <src.res@email.cn> Cc: Paolo Bonzini <pbonzini@redhat.com> Acked-by: Catalin Marinas <catalin.marinas@arm.com> Reviewed-by: Yantengsi <siyanteng@loongson.cn> Signed-off-by: Jonathan Corbet <corbet@lwn.net>