From: Yicong Yang <yangyicong@hisilicon.com> commit 5deb9c789ae468a71a7c11c92d21769f7cbf68fa upstream. commit 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 upstream. On building the topology from the devicetree, we've already gotten the SMT thread number of each core. Update the largest SMT thread number and enable the SMT control by the end of topology parsing. The framework's SMT control provides two interface to the users [1] through /sys/devices/system/cpu/smt/control: 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. [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Docu... Reviewed-by: Pierre Gondois <pierre.gondois@arm.com> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Reviewed-by: Yicong Yang <yangyicong@hisilicon.com> Signed-off-by: Yicong Yang <yangyicong@hisilicon.com> Signed-off-by: Hongye Lin <linhongye@h-partners.com> Signed-off-by: Qi Xi <xiqi2@huawei.com> --- drivers/base/arch_topology.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c index 1dddf518da0a..76244508ccc8 100644 --- a/drivers/base/arch_topology.c +++ b/drivers/base/arch_topology.c @@ -16,6 +16,7 @@ #include <linux/sched/topology.h> #include <linux/cpuset.h> #include <linux/cpumask.h> +#include <linux/cpu_smt.h> #include <linux/init.h> #include <linux/percpu.h> #include <linux/rcupdate.h> @@ -390,6 +391,10 @@ core_initcall(free_raw_capacity); #endif #if defined(CONFIG_ARM64) || defined(CONFIG_RISCV) + +/* Used to enable the SMT control */ +static unsigned int max_smt_thread_num = 1; + /* * This function returns the logic cpu number of the node. * There are basically three kinds of return values: @@ -449,6 +454,8 @@ static int __init parse_core(struct device_node *core, int package_id, i++; } while (t); + max_smt_thread_num = max_t(unsigned int, max_smt_thread_num, i); + cpu = get_cpu_for_node(core); if (cpu >= 0) { if (!leaf) { @@ -554,6 +561,17 @@ static int __init parse_socket(struct device_node *socket) if (!has_socket) ret = parse_cluster(socket, 0, 0); + /* + * Reset the max_smt_thread_num to 1 on failure. Since on failure + * we need to notify the framework the SMT is not supported, but + * max_smt_thread_num can be initialized to the SMT thread number + * of the cores which are successfully parsed. + */ + if (ret) + max_smt_thread_num = 1; + + cpu_smt_set_num_threads(max_smt_thread_num, max_smt_thread_num); + return ret; } -- 2.33.0