--- zzzz-none-000/linux-3.18.24/arch/mips/kernel/smp.c	2015-10-31 20:39:51.000000000 +0000
+++ rtl96-5690pro-762/linux-3.18.24/arch/mips/kernel/smp.c	2024-08-14 08:36:36.000000000 +0000
@@ -42,7 +42,9 @@
 #include <asm/mmu_context.h>
 #include <asm/time.h>
 #include <asm/setup.h>
-
+#ifdef PLAT_QEMU
+extern int plat_qemu;
+#endif
 volatile cpumask_t cpu_callin_map;	/* Bitmask of started secondaries */
 
 int __cpu_number_map[NR_CPUS];		/* Map physical to logical */
@@ -63,6 +65,13 @@
 cpumask_t cpu_core_map[NR_CPUS] __read_mostly;
 EXPORT_SYMBOL(cpu_core_map);
 
+/*
+ * A logcal cpu mask containing only one VPE per core to
+ * reduce the number of IPIs on large MT systems.
+ */
+cpumask_t cpu_foreign_map __read_mostly;
+EXPORT_SYMBOL(cpu_foreign_map);
+
 /* representing cpus for which sibling maps can be computed */
 static cpumask_t cpu_sibling_setup_map;
 
@@ -103,6 +112,29 @@
 	}
 }
 
+/*
+ * Calculate a new cpu_foreign_map mask whenever a
+ * new cpu appears or disappears.
+ */
+static inline void calculate_cpu_foreign_map(void)
+{
+	int i, k, core_present;
+	cpumask_t temp_foreign_map;
+
+	/* Re-calculate the mask */
+	for_each_online_cpu(i) {
+		core_present = 0;
+		for_each_cpu(k, &temp_foreign_map)
+			if (cpu_data[i].package == cpu_data[k].package &&
+			    cpu_data[i].core == cpu_data[k].core)
+				core_present = 1;
+		if (!core_present)
+			cpumask_set_cpu(i, &temp_foreign_map);
+	}
+
+	cpumask_copy(&cpu_foreign_map, &temp_foreign_map);
+}
+
 struct plat_smp_ops *mp_ops;
 EXPORT_SYMBOL(mp_ops);
 
@@ -146,8 +178,12 @@
 	set_cpu_sibling_map(cpu);
 	set_cpu_core_map(cpu);
 
-	cpu_set(cpu, cpu_callin_map);
+	calculate_cpu_foreign_map();
 
+	cpu_set(cpu, cpu_callin_map);
+#ifdef PLAT_QEMU
+	if (!plat_qemu)
+#endif
 	synchronise_count_slave(cpu);
 
 	/*
@@ -173,13 +209,20 @@
 static void stop_this_cpu(void *dummy)
 {
 	/*
-	 * Remove this CPU:
+	 * Remove this CPU. Be a bit slow here and
+	 * set the bits for every online CPU so we don't miss
+	 * any IPI whilst taking this VPE down.
 	 */
+
+	cpumask_copy(&cpu_foreign_map, cpu_online_mask);
+
+	/* Make it visible to every other CPU */
+	smp_mb();
+
 	set_cpu_online(smp_processor_id(), false);
-	for (;;) {
-		if (cpu_wait)
-			(*cpu_wait)();		/* Wait if available. */
-	}
+	calculate_cpu_foreign_map();
+	local_irq_disable();
+	while (1);
 }
 
 void smp_send_stop(void)
@@ -199,6 +242,7 @@
 	mp_ops->prepare_cpus(max_cpus);
 	set_cpu_sibling_map(0);
 	set_cpu_core_map(0);
+	calculate_cpu_foreign_map();
 #ifndef CONFIG_HOTPLUG_CPU
 	init_cpu_present(cpu_possible_mask);
 #endif
@@ -222,7 +266,9 @@
 	 */
 	while (!cpu_isset(cpu, cpu_callin_map))
 		udelay(100);
-
+#ifdef PLAT_QEMU
+	if (!plat_qemu)
+#endif
 	synchronise_count_master(cpu);
 	return 0;
 }