[PATCH] UP local APIC bootstrap cleanup

Here is a patch to do some cleanup to code affected by the recent change to
the bootstrap code responsible for enabling the local APIC.  It adds a
message about how to get the APIC enabled if previously disabled by the
BIOS to aid people expecting the former behavior.  It removes some
P4-specific code that's become dead as a result of the change.  Finally it
improves a couple of inaccurate comments.

This has been agreed to be reasonable.
Signed-off-by: "Maciej W. Rozycki" <macro@linux-mips.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/i386/kernel/apic.c

@@ -689,7 +689,7 @@ static int __init detect_init_APIC (void)
 	u32 h, l, features;
 	extern void get_cpu_vendor(struct cpuinfo_x86*);
 
-	/* Disabled by DMI scan or kernel option? */
+	/* Disabled by kernel option? */
 	if (enable_local_apic < 0)
 		return -1;
 
@@ -703,8 +703,7 @@ static int __init detect_init_APIC (void)
 			break;
 		goto no_apic;
 	case X86_VENDOR_INTEL:
-		if (boot_cpu_data.x86 == 6 ||
-		    (boot_cpu_data.x86 == 15 && (cpu_has_apic || enable_local_apic > 0)) ||
+		if (boot_cpu_data.x86 == 6 || boot_cpu_data.x86 == 15 ||
 		    (boot_cpu_data.x86 == 5 && cpu_has_apic))
 			break;
 		goto no_apic;
@@ -714,15 +713,20 @@ static int __init detect_init_APIC (void)
 
 	if (!cpu_has_apic) {
 		/*
-		 * Over-ride BIOS and try to enable LAPIC
-		 * only if "lapic" specified
+		 * Over-ride BIOS and try to enable the local
+		 * APIC only if "lapic" specified.
 		 */
-		if (enable_local_apic != 1)
-			goto no_apic;
+		if (enable_local_apic <= 0) {
+			apic_printk(APIC_VERBOSE,
+				    "Local APIC disabled by BIOS -- "
+				    "you can enable it with \"lapic\"\n");
+			return -1;
+		}
 		/*
 		 * Some BIOSes disable the local APIC in the
 		 * APIC_BASE MSR. This can only be done in
-		 * software for Intel P6 and AMD K7 (Model > 1).
+		 * software for Intel P6 or later and AMD K7
+		 * (Model > 1) or later.
 		 */
 		rdmsr(MSR_IA32_APICBASE, l, h);
 		if (!(l & MSR_IA32_APICBASE_ENABLE)) {