arm64: Add irq aff change check

For aarch64, the PPIs format in /proc/interrputs can be parsed and add to interrupt db, and next, the number of interrupts is counted and used to calculate the load. Finally these interrupts maybe scheduled between the NUMA domains.

Acctually, the PPIs cannot change aff, and it should not be added to interrupt db. This patch fix it.

Add a check before add a interrupt to db, just only reads the irq's aff, and write it back to avoid any impact on the system, According to the result of writing to fitler the irq.

classify.c

@@ -280,6 +280,13 @@ static void add_banned_irq(int irq, GList **list)
 	return;
 }
 
+#ifdef AARCH64
+void add_banned_list_irq(int irq)
+{
+	add_banned_irq(irq, &banned_irqs);
+}
+#endif
+
 void add_cl_banned_irq(int irq)
 {
 	add_banned_irq(irq, &cl_banned_irqs);

irqbalance.h

@@ -101,6 +101,9 @@ extern int get_cpu_count(void);
 extern void rebuild_irq_db(void);
 extern void free_irq_db(void);
 extern void add_cl_banned_irq(int irq);
+#ifdef AARCH64
+extern void add_banned_list_irq(int irq);
+#endif
 extern void for_each_irq(GList *list, void (*cb)(struct irq_info *info,  void *data), void *data);
 extern struct irq_info *get_irq_info(int irq);
 extern void migrate_irq(GList **from, GList **to, struct irq_info *info);

procinterrupts.c

@@ -143,6 +143,36 @@ static void guess_arm_irq_hints(char *name, struct irq_info *info)
 
 
 }
+
+static int is_arm_irq_aff_cannot_change(int irq)
+{
+	char buf[PATH_MAX] = { 0 };
+	FILE *file = NULL;
+	char *line = NULL;
+	size_t size = 0;
+	int ret = 0;
+
+	snprintf(buf, PATH_MAX - 1, "/proc/irq/%i/smp_affinity", irq);
+	file = fopen(buf, "r+");
+	if (!file)
+		return -1;
+
+	if (getline(&line, &size, file) <= 0) {
+		ret = -1;
+		goto out;
+	}
+
+	line[strlen(line) - 1] = '\0';
+
+	fprintf(file, "%s", line);
+	ret = fflush(file);
+
+out:
+	free(line);
+	fclose(file);
+
+	return ret;
+}
 #endif
 
 GList* collect_full_irq_list()
@@ -214,6 +244,24 @@ GList* collect_full_irq_list()
 		*c = 0;
 		number = strtoul(line, NULL, 10);
 
+#ifdef AARCH64
+		if (is_arm_irq_aff_cannot_change(number)) {
+			/*
+			 * This means that the irq affinity cannot be changed, just like:
+			 * (1) the irq with IRQF_PERCPU flag,  per cpu irq (in arm64, like PPI)
+			 * (2) the irq with IRQD_NO_BALANCING flag, some driver request irq can
+			 *     set the flag according to themselves require. for example in arm64,
+			 *     for the passthrough doorbell irq (GICV4), in future.
+			 * (3) the irq with IRQD_AFFINITY_MANAGED flag, some drivers can set
+			 *     specially irq affinity, and prohibit user to modify it.
+			 *
+			 * For these irqs, we can add these to banned irq list.
+			 */
+			add_banned_list_irq(number);
+			continue;
+		}
+#endif
+
 		info = calloc(1, sizeof(struct irq_info));
 		if (info) {
 			info->irq = number;