powerpc: remove cpu_online_cores_map function

This function builds the cores online map with on-stack cpumasks which
can cause high stack usage with large NR_CPUS.

It is not used in any performance sensitive paths, so instead just check
for first thread sibling.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Tested-by: Sachin Sant <sachinp@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20211105035042.1398309-1-npiggin@gmail.com

3 files changed, 8 insertions, 41 deletions

diff --git a/arch/powerpc/include/asm/cputhreads.h b/arch/powerpc/include/asm/cputhreads.h
index b167186aaee4..f26c430f3982 100644
--- a/arch/powerpc/include/asm/cputhreads.h
+++ b/arch/powerpc/include/asm/cputhreads.h
@@ -32,44 +32,11 @@ extern cpumask_t threads_core_mask;
 #define threads_core_mask	(*get_cpu_mask(0))
 #endif
 
-/* cpu_thread_mask_to_cores - Return a cpumask of one per cores
- *                            hit by the argument
- *
- * @threads:	a cpumask of online threads
- *
- * This function returns a cpumask which will have one online cpu's
- * bit set for each core that has at least one thread set in the argument.
- *
- * This can typically be used for things like IPI for tlb invalidations
- * since those need to be done only once per core/TLB
- */
-static inline cpumask_t cpu_thread_mask_to_cores(const struct cpumask *threads)
-{
-	cpumask_t	tmp, res;
-	int		i, cpu;
-
-	cpumask_clear(&res);
-	for (i = 0; i < NR_CPUS; i += threads_per_core) {
-		cpumask_shift_left(&tmp, &threads_core_mask, i);
-		if (cpumask_intersects(threads, &tmp)) {
-			cpu = cpumask_next_and(-1, &tmp, cpu_online_mask);
-			if (cpu < nr_cpu_ids)
-				cpumask_set_cpu(cpu, &res);
-		}
-	}
-	return res;
-}
-
 static inline int cpu_nr_cores(void)
 {
 	return nr_cpu_ids >> threads_shift;
 }
 
-static inline cpumask_t cpu_online_cores_map(void)
-{
-	return cpu_thread_mask_to_cores(cpu_online_mask);
-}
-
 #ifdef CONFIG_SMP
 int cpu_core_index_of_thread(int cpu);
 int cpu_first_thread_of_core(int core);
diff --git a/arch/powerpc/platforms/powernv/idle.c b/arch/powerpc/platforms/powernv/idle.c
index 3bc84e2fe064..95458fd9572c 100644
--- a/arch/powerpc/platforms/powernv/idle.c
+++ b/arch/powerpc/platforms/powernv/idle.c
@@ -146,9 +146,13 @@ EXPORT_SYMBOL_GPL(pnv_get_supported_cpuidle_states);
 static void pnv_fastsleep_workaround_apply(void *info)
 
 {
+	int cpu = smp_processor_id();
 	int rc;
 	int *err = info;
 
+	if (cpu_first_thread_sibling(cpu) != cpu)
+		return;
+
 	rc = opal_config_cpu_idle_state(OPAL_CONFIG_IDLE_FASTSLEEP,
 					OPAL_CONFIG_IDLE_APPLY);
 	if (rc)
@@ -175,7 +179,6 @@ static ssize_t store_fastsleep_workaround_applyonce(struct device *dev,
 		struct device_attribute *attr, const char *buf,
 		size_t count)
 {
-	cpumask_t primary_thread_mask;
 	int err;
 	u8 val;
 
@@ -200,10 +203,7 @@ static ssize_t store_fastsleep_workaround_applyonce(struct device *dev,
 	power7_fastsleep_workaround_exit = false;
 
 	cpus_read_lock();
-	primary_thread_mask = cpu_online_cores_map();
-	on_each_cpu_mask(&primary_thread_mask,
-				pnv_fastsleep_workaround_apply,
-				&err, 1);
+	on_each_cpu(pnv_fastsleep_workaround_apply, &err, 1);
 	cpus_read_unlock();
 	if (err) {
 		pr_err("fastsleep_workaround_applyonce change failed while running pnv_fastsleep_workaround_apply");
diff --git a/arch/powerpc/platforms/powernv/opal-imc.c b/arch/powerpc/platforms/powernv/opal-imc.c
index 05d3832019b9..3fea5da6d1b3 100644
--- a/arch/powerpc/platforms/powernv/opal-imc.c
+++ b/arch/powerpc/platforms/powernv/opal-imc.c
@@ -200,13 +200,13 @@ static void disable_nest_pmu_counters(void)
 
 static void disable_core_pmu_counters(void)
 {
-	cpumask_t cores_map;
 	int cpu, rc;
 
 	cpus_read_lock();
 	/* Disable the IMC Core functions */
-	cores_map = cpu_online_cores_map();
-	for_each_cpu(cpu, &cores_map) {
+	for_each_online_cpu(cpu) {
+		if (cpu_first_thread_sibling(cpu) != cpu)
+			continue;
 		rc = opal_imc_counters_stop(OPAL_IMC_COUNTERS_CORE,
 					    get_hard_smp_processor_id(cpu));
 		if (rc)