{arch,cpu}/x86, drivers/intel: Restore cpu_index error handling

Previously cpu_index() always succeeded, but since commit 095c931
(src/arch/x86: Use core apic id to get cpu_index()) it is now possible
for it to indicate an error by returning -1. This commit adds error
handling for all calls to cpu_index(), and restores several checks that
were removed in commit 7c712bb (Fix code that would trip -Wtype-limits)
but are now needed.

Signed-off-by: Jacob Garber <jgarber1@ualberta.ca>
Change-Id: I5436eed4cb5675f916924eb9670db04592a8b927
Reviewed-on: https://review.coreboot.org/c/coreboot/+/32795
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

src/cpu/x86/mp_init.c

@@ -870,13 +870,20 @@ static int run_ap_work(struct mp_callback *val, long expire_us)
 	int i;
 	int cpus_accepted;
 	struct stopwatch sw;
-	int cur_cpu = cpu_index();
+	int cur_cpu;
 
 	if (!CONFIG(PARALLEL_MP_AP_WORK)) {
 		printk(BIOS_ERR, "APs already parked. PARALLEL_MP_AP_WORK not selected.\n");
 		return -1;
 	}
 
+	cur_cpu = cpu_index();
+
+	if (cur_cpu < 0) {
+		printk(BIOS_ERR, "Invalid CPU index.\n");
+		return -1;
+	}
+
 	/* Signal to all the APs to run the func. */
 	for (i = 0; i < ARRAY_SIZE(ap_callbacks); i++) {
 		if (cur_cpu == i)
@@ -918,6 +925,12 @@ static void ap_wait_for_instruction(void)
 		return;
 
 	cur_cpu = cpu_index();
+
+	if (cur_cpu < 0) {
+		printk(BIOS_ERR, "Invalid CPU index.\n");
+		return;
+	}
+
 	per_cpu_slot = &ap_callbacks[cur_cpu];
 
 	while (1) {

src/cpu/x86/pae/pgtbl.c

@@ -116,12 +116,12 @@ void *map_2M_page(unsigned long page)
 	static struct pg_table pgtbl[CONFIG_MAX_CPUS]
 		__attribute__((aligned(4096)));
 	static unsigned long mapped_window[CONFIG_MAX_CPUS];
-	unsigned long index;
+	int index;
 	unsigned long window;
 	void *result;
 	int i;
 	index = cpu_index();
-	if (index >= CONFIG_MAX_CPUS)
+	if (index < 0)
 		return MAPPING_ERROR;
 	window = page >> 10;
 	if (window != mapped_window[index]) {