x86: clean up max_pfn_mapped usage - 32-bit

on 32-bit in head_32.S after initial page table is done, we get initial
max_pfn_mapped, and then kernel_physical_mapping_init will give us
a final one.

We need to use that to make sure find_e820_area will get valid addresses
for boot_map and for NODE_DATA(0) on numa32.

XEN PV and lguest may need to assign max_pfn_mapped too.
Signed-off-by: NYinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

arch/x86/kernel/head_32.S

@@ -220,6 +220,8 @@ default_entry:
 	jb 10b
 1:
 	movl %edi,pa(init_pg_tables_end)
+	shrl $12, %eax
+	movl %eax, pa(max_pfn_mapped)
 
 	/* Do early initialization of the fixmap area */
 	movl $pa(swapper_pg_fixmap)+PDE_ATTR,%eax
@@ -251,6 +253,8 @@ page_pde_offset = (__PAGE_OFFSET >> 20);
 	cmpl %ebp,%eax
 	jb 10b
 	movl %edi,pa(init_pg_tables_end)
+	shrl $12, %eax
+	movl %eax, pa(max_pfn_mapped)
 
 	/* Do early initialization of the fixmap area */
 	movl $pa(swapper_pg_fixmap)+PDE_ATTR,%eax

arch/x86/kernel/setup_32.c

@@ -586,7 +586,7 @@ void __init setup_bootmem_allocator(void)
 	 */
 	bootmap_size = bootmem_bootmap_pages(max_low_pfn)<<PAGE_SHIFT;
 	bootmap = find_e820_area(min_low_pfn<<PAGE_SHIFT,
-				 max_low_pfn<<PAGE_SHIFT, bootmap_size,
+				 max_pfn_mapped<<PAGE_SHIFT, bootmap_size,
 				 PAGE_SIZE);
 	if (bootmap == -1L)
 		panic("Cannot find bootmem map of size %ld\n", bootmap_size);
@@ -595,6 +595,8 @@ void __init setup_bootmem_allocator(void)
 	reserve_initrd();
 #endif
 	bootmap_size = init_bootmem(bootmap >> PAGE_SHIFT, max_low_pfn);
+	printk(KERN_INFO "  mapped low ram: 0 - %08lx\n",
+		 max_pfn_mapped<<PAGE_SHIFT);
 	printk(KERN_INFO "  low ram: %08lx - %08lx\n",
 		 min_low_pfn<<PAGE_SHIFT, max_low_pfn<<PAGE_SHIFT);
 	printk(KERN_INFO "  bootmap %08lx - %08lx\n",

arch/x86/mm/discontig_32.c

@@ -163,7 +163,8 @@ static void __init allocate_pgdat(int nid)
 	else {
 		unsigned long pgdat_phys;
 		pgdat_phys = find_e820_area(min_low_pfn<<PAGE_SHIFT,
-				 max_low_pfn<<PAGE_SHIFT, sizeof(pg_data_t),
+				 (nid ? max_low_pfn:max_pfn_mapped)<<PAGE_SHIFT,
+				 sizeof(pg_data_t),
 				 PAGE_SIZE);
 		NODE_DATA(nid) = (pg_data_t *)(pfn_to_kaddr(pgdat_phys>>PAGE_SHIFT));
 		reserve_early(pgdat_phys, pgdat_phys + sizeof(pg_data_t),