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For ACPI we'll build the topology from PPTT and we cannot directly get the SMT number of each core. Instead using a temporary xarray to record the heterogeneous information (from ACPI_PPTT_ACPI_IDENTICAL) and SMT information of the first core in its heterogeneous CPU cluster when building the topology. Then we can know the largest SMT number in the system. If a homogeneous system's using ACPI 6.2 or later, all the CPUs should be under the root node of PPTT. There'll be only one entry in the xarray and all the CPUs in the system will be assumed identical. The framework's SMT control provides two interface to the users [1] through /sys/devices/system/cpu/smt/control (Documentation/ABI/testing/sysfs-devices-system-cpu): 1) enable SMT by writing "on" and disable by "off" 2) enable SMT by writing max_thread_number or disable by writing 1 Both method support to completely disable/enable the SMT cores so both work correctly for symmetric SMT platform and asymmetric platform with non-SMT and one type SMT cores like: core A: 1 thread core B: X (X!=1) threads Note that for a theoretically possible multiple SMT-X (X>1) core platform the SMT control is also supported as expected but only by writing the "on/off" method. Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> Reviewed-by: Hanjun Guo <guohanjun@huawei.com> Reviewed-by: Pierre Gondois <pierre.gondois@arm.com> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Signed-off-by: Yicong Yang <yangyicong@hisilicon.com> Reviewed-by: Sudeep Holla <sudeep.holla@arm.com> Link: https://lore.kernel.org/r/20250311075143.61078-4-yangyicong@huawei.com Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.