kernel: add support for getting percpu variables that belong to other CPUs

kernel/cpu.c

@@ -12,11 +12,34 @@ struct cpu_data *get_this_cpu(void)
 	return percpu_get(&cpu_data);
 }
 
+struct cpu_data *get_cpu(unsigned int id)
+{
+	return percpu_get_from(id, &cpu_data);
+}
+
 void put_cpu(struct cpu_data *cpu)
 {
 	percpu_put(cpu);
 }
 
+bool cpu_is_available(unsigned int cpu_id)
+{
+	if (cpu_id >= CPU_MAX) {
+		return false;
+	}
+
+	return bitmap_check(cpu_available, cpu_id);
+}
+
+bool cpu_is_online(unsigned int cpu_id)
+{
+	if (cpu_id >= CPU_MAX) {
+		return false;
+	}
+
+	return bitmap_check(cpu_online, cpu_id);
+}
+
 void cpu_set_available(unsigned int cpu_id)
 {
 	if (cpu_id >= CPU_MAX) {

kernel/percpu.c

@@ -24,7 +24,7 @@ extern kern_status_t init_per_cpu_areas(void)
 	return KERN_OK;
 }
 
-extern void *__percpu_get(void *var)
+extern void *__percpu_get(unsigned int cpu, void *var)
 {
 	uintptr_t pvar = (uintptr_t)var;
 	uintptr_t percpu_start = (uintptr_t)__percpu_start;
@@ -36,5 +36,5 @@ extern void *__percpu_get(void *var)
 
 	size_t var_offset = pvar - percpu_start;
 
-	return (char *)percpu_buffer + (this_cpu() * percpu_stride) + var_offset;
+	return (char *)percpu_buffer + (cpu * percpu_stride) + var_offset;
 }