[PATCH] i386: Handle non existing APICs without panicing

[description from AK]

This fixes booting in APIC mode on some ACER laptops. x86-64
did a similar change some time ago.

See http://bugzilla.kernel.org/show_bug.cgi?id=4700 for details
Signed-off-by: NAndi Kleen <ak@suse.de>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

arch/i386/kernel/io_apic.c

@@ -2566,8 +2566,10 @@ int __init io_apic_get_unique_id (int ioapic, int apic_id)
 		spin_unlock_irqrestore(&ioapic_lock, flags);
 
 		/* Sanity check */
-		if (reg_00.bits.ID != apic_id)
-			panic("IOAPIC[%d]: Unable change apic_id!\n", ioapic);
+		if (reg_00.bits.ID != apic_id) {
+			printk("IOAPIC[%d]: Unable to change apic_id!\n", ioapic);
+			return -1;
+		}
 	}
 
 	apic_printk(APIC_VERBOSE, KERN_INFO

arch/i386/kernel/mpparse.c

@@ -915,6 +915,7 @@ void __init mp_register_ioapic (
 	u32			gsi_base)
 {
 	int			idx = 0;
+	int			tmpid;
 
 	if (nr_ioapics >= MAX_IO_APICS) {
 		printk(KERN_ERR "ERROR: Max # of I/O APICs (%d) exceeded "
@@ -935,9 +936,14 @@ void __init mp_register_ioapic (
 
 	set_fixmap_nocache(FIX_IO_APIC_BASE_0 + idx, address);
 	if ((boot_cpu_data.x86_vendor == X86_VENDOR_INTEL) && (boot_cpu_data.x86 < 15))
-		mp_ioapics[idx].mpc_apicid = io_apic_get_unique_id(idx, id);
+		tmpid = io_apic_get_unique_id(idx, id);
 	else
-		mp_ioapics[idx].mpc_apicid = id;
+		tmpid = id;
+	if (tmpid == -1) {
+		nr_ioapics--;
+		return;
+	}
+	mp_ioapics[idx].mpc_apicid = tmpid;
 	mp_ioapics[idx].mpc_apicver = io_apic_get_version(idx);
 	
 	/*