[RFC PATCH v3 04/13] LoongArch: Configure sbm topology during SMP preparation
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From: K Prateek Nayak <kprateek.nayak@amd.com>
Date: 2026-10-01 19:30:59
Also in:
driver-core, linux-arch, linux-mips, linux-s390, lkml, loongarch
Subsystem:
loongarch, the rest · Maintainers:
Huacai Chen, Linus Torvalds
Revision v3 of 2 in this series.
Revisions (2)
- v3 current
- v3
Configure the sparsebitmask (sbm) topology for multi-node processors once SRAT is parsed and cpu_to_node() mappings are stable. Former commit enabled parsing node mappings for disabled CPUs during SRAT parsing and every CPU will have a valid mapping before the sbm topology parsing is attempted ensuring correct bounds for max_threads_per_instance. XXX: If _PXM mappings cannot be trusted for disabled CPUs, an alternate logic needs to be added. See PowerPC enablement later in the series. Signed-off-by: K Prateek Nayak <kprateek.nayak@amd.com> --- Only build tested with config from https://lore.kernel.org/lkml/202609190905.OZTcO07l-lkp@intel.com/ (local) --- arch/loongarch/kernel/smp.c | 36 ++++++++++++++++++++++++++++++++++++ 1 file changed, 36 insertions(+)
diff --git a/arch/loongarch/kernel/smp.c b/arch/loongarch/kernel/smp.c
index d4b5d1b6bb01..d8155b26c4df 100644
--- a/arch/loongarch/kernel/smp.c
+++ b/arch/loongarch/kernel/smp.c@@ -15,6 +15,7 @@ #include <linux/interrupt.h> #include <linux/irq_work.h> #include <linux/profile.h> +#include <linux/sbm.h> #include <linux/seq_file.h> #include <linux/smp.h> #include <linux/threads.h>
@@ -73,6 +74,10 @@ static cpumask_t cpu_llc_shared_setup_map; /* representing cpus for which core maps can be computed */ static cpumask_t cpu_core_setup_map; +/* sbm setup data - only needed during init */ +static cpumask_t cpu_sbm_setup_map __initdata; +static int __node_thread_count[NR_CPUS] __initdata; + struct secondary_data cpuboot_data; static DEFINE_PER_CPU(int, cpu_state);
@@ -362,10 +367,16 @@ void __init loongson_smp_setup(void) pr_info("Detected %i available CPU(s)\n", loongson_sysconf.nr_cpus); } +int arch_sbm_cpu_instance_id(int cpu) +{ + return cpu_to_node(cpu); +} + void __init loongson_prepare_cpus(unsigned int max_cpus) { int i = 0; int threads_per_core = 0; + int num_sbm_instances, max_threads_per_instance = 1; parse_acpi_topology(); cpu_data[0].global_id = cpu_logical_map(0);
@@ -388,6 +399,31 @@ void __init loongson_prepare_cpus(unsigned int max_cpus) per_cpu(cpu_state, smp_processor_id()) = CPU_ONLINE; cpu_smt_set_num_threads(threads_per_core, threads_per_core); + + for_each_possible_cpu(i) { + bool found = false; + int j; + + for_each_cpu(j, &cpu_sbm_setup_map) { + if (cpu_to_node(i) == cpu_to_node(j)) { + found = true; + break; + } + } + + if (!found) { + cpumask_set_cpu(i, &cpu_sbm_setup_map); + __node_thread_count[i] = 1; + continue; + } + + __node_thread_count[j] += 1; + max_threads_per_instance = max(max_threads_per_instance, + __node_thread_count[j]); + } + + num_sbm_instances = cpumask_weight(&cpu_sbm_setup_map); + sbm_set_topology(num_sbm_instances, max_threads_per_instance); } /*
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2.34.1