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4ffa09a939
Because of the effect of SVE on the size of the signal frame, the default vector length used for new processes involves a tradeoff between performance of SVE-enabled software on the one hand, and reliability of non-SVE-aware software on the other hand. For this reason, the best choice depends on the repertoire of userspace software in use and is thus best left up to distro maintainers, sysadmins and developers. If CONFIG_SYSCTL and CONFIG_PROC_SYSCTL are enabled, this patch exposes the default vector length in /proc/sys/abi/sve_default_vector_length, where boot scripts or the adventurous can poke it. In common with other arm64 ABI sysctls, this control is currently global: setting it requires CAP_SYS_ADMIN in the root user namespace, but the value set is effective for subsequent execs in all namespaces. The control only affects _new_ processes, however: changing it does not affect the vector length of any existing process. The intended usage model is that if userspace is known to be fully SVE-tolerant (or a developer is curious to find out) then this parameter can be cranked up during system startup. Signed-off-by: Dave Martin <Dave.Martin@arm.com> Reviewed-by: Alex Bennée <alex.bennee@linaro.org> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> |
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| boot | ||
| configs | ||
| crypto | ||
| include | ||
| kernel | ||
| kvm | ||
| lib | ||
| mm | ||
| net | ||
| xen | ||
| Kconfig | ||
| Kconfig.debug | ||
| Kconfig.platforms | ||
| Makefile | ||