x86: insert_resorce for lapic addr after e820_reserve_resources

when comparing the e820 direct from BIOS, and the one by kexec:

 BIOS-provided physical RAM map:
- BIOS-e820: 0000000000000000 - 0000000000097400 (usable)
+ BIOS-e820: 0000000000000100 - 0000000000097400 (usable)
  BIOS-e820: 0000000000097400 - 00000000000a0000 (reserved)
  BIOS-e820: 00000000000e6000 - 0000000000100000 (reserved)
  BIOS-e820: 0000000000100000 - 00000000dffa0000 (usable)
- BIOS-e820: 00000000dffae000 - 00000000dffb0000 type 9
+ BIOS-e820: 00000000dffae000 - 00000000dffb0000 (reserved)
  BIOS-e820: 00000000dffb0000 - 00000000dffbe000 (ACPI data)
  BIOS-e820: 00000000dffbe000 - 00000000dfff0000 (ACPI NVS)
  BIOS-e820: 00000000dfff0000 - 00000000e0000000 (reserved)
  BIOS-e820: 00000000fec00000 - 00000000fec01000 (reserved)
- BIOS-e820: 00000000fee00000 - 00000000fee01000 (reserved)
             =======> that is the local apic address... somewhere we lost it
  BIOS-e820: 00000000ff700000 - 0000000100000000 (reserved)
  BIOS-e820: 0000000100000000 - 0000004020000000 (usable)

found one entry about reserved is missing for the kernel by kexec.

it turns out init_apic_mappings is called before e820_reserve_resources
in setup_arch. but e820_reserve_resources is using request_resource.
it will not handle the conflicts.

there are three ways to fix it:

1. change request_resource in e820_reserve_resources to to insert_resource
2. move init_apic_mappings after e820_reserve_resources
3. use late_initcall to insert lapic resource.

this patch is using method 3, that is less intrusive.

in later version could consider to use method 1.

before patch
fed20000-ffffffff : PCI Bus #00
  fee00000-fee00fff : Local APIC
  fefff000-feffffff : pnp 00:09
  ff700000-ffffffff : reserved

with patch will get map in first kernel

fed20000-ffffffff : PCI Bus #00
  fee00000-fee00fff : Local APIC
    fee00000-fee00fff : reserved
  fefff000-feffffff : pnp 00:09
  ff700000-ffffffff : reserved
Signed-off-by: Yinghai Lu <yinghai.lu@sun.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/apic_64.c

@@ -881,11 +881,6 @@ void __init init_apic_mappings(void)
 	apic_printk(APIC_VERBOSE, "mapped APIC to %16lx (%16lx)\n",
 				APIC_BASE, apic_phys);
 
-	/* Put local APIC into the resource map. */
-	lapic_resource.start = apic_phys;
-	lapic_resource.end = lapic_resource.start + PAGE_SIZE - 1;
-	insert_resource(&iomem_resource, &lapic_resource);
-
 	/*
 	 * Fetch the APIC ID of the BSP in case we have a
 	 * default configuration (or the MP table is broken).
@@ -1300,3 +1295,21 @@ static __init int setup_apicpmtimer(char *s)
 }
 __setup("apicpmtimer", setup_apicpmtimer);
 
+static int __init lapic_insert_resource(void)
+{
+	if (!apic_phys)
+		return -1;
+
+	/* Put local APIC into the resource map. */
+	lapic_resource.start = apic_phys;
+	lapic_resource.end = lapic_resource.start + PAGE_SIZE - 1;
+	insert_resource(&iomem_resource, &lapic_resource);
+
+	return 0;
+}
+
+/*
+ * need call insert after e820_reserve_resources()
+ * that is using request_resource
+ */
+late_initcall(lapic_insert_resource);