Hi Matt,

FYI, starting from this commit, the kernel immediately reboots in my
kvm boot tests..

Thanks,
Fengguang

commit a790068f4435a053fa16562eceed520f9b027c41
Author: Matt Fleming <matt.fleming@intel.com>
Date:   Mon Mar 5 14:21:35 2012 +0000

    x86, efi: Fixup efi_ioremap() breakage
    
    Don't map holes.
    
     * Is the e820 map the correct memory map to use?
     * Is it OK to call find_early_table_space multiple times?
     * Do we need add_efi_memmap anymore? Unconditionally do it?
     * Should we reduce freq of printk(init_memory_mapping);?
     * Are there parts of the memmap not in the e820 map?
     * Do we even need to map ACPI stuff? is it ioremap'd?
     * Is it save to reserve pagetables in init_memory_mapping(), are the other callers (gart_iommu) called after bootmem?
    
    Signed-off-by: Matt Fleming <matt.fleming@intel.com>

diff --git a/arch/x86/include/asm/page_types.h b/arch/x86/include/asm/page_types.h
index bce688d..4f95f23 100644
--- a/arch/x86/include/asm/page_types.h
+++ b/arch/x86/include/asm/page_types.h
@@ -51,8 +51,9 @@ static inline phys_addr_t get_max_mapped(void)
 	return (phys_addr_t)max_pfn_mapped << PAGE_SHIFT;
 }
 
-extern unsigned long init_memory_mapping(unsigned long start,
-					 unsigned long end);
+extern unsigned long init_memory_mapping(void);
+extern unsigned long __init_memory_mapping(unsigned long start,
+					   unsigned long end);
 
 extern void initmem_init(void);
 extern void free_initmem(void);
diff --git a/arch/x86/kernel/amd_gart_64.c b/arch/x86/kernel/amd_gart_64.c
index b1e7c7f..f52ced2 100644
--- a/arch/x86/kernel/amd_gart_64.c
+++ b/arch/x86/kernel/amd_gart_64.c
@@ -769,7 +769,7 @@ int __init gart_iommu_init(void)
 
 	if (end_pfn > max_low_pfn_mapped) {
 		start_pfn = (aper_base>>PAGE_SHIFT);
-		init_memory_mapping(start_pfn<<PAGE_SHIFT, end_pfn<<PAGE_SHIFT);
+		__init_memory_mapping(start_pfn<<PAGE_SHIFT, end_pfn<<PAGE_SHIFT);
 	}
 
 	pr_info("PCI-DMA: using GART IOMMU.\n");
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index e22bb08..b65d287 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -690,8 +690,6 @@ early_param("reservelow", parse_reservelow);
 
 void __init setup_arch(char **cmdline_p)
 {
-	unsigned long end_pfn;
-
 #ifdef CONFIG_X86_32
 	memcpy(&boot_cpu_data, &new_cpu_data, sizeof(new_cpu_data));
 	visws_early_detect();
@@ -927,31 +925,11 @@ void __init setup_arch(char **cmdline_p)
 
 	init_gbpages();
 
-	/* max_pfn_mapped is updated here */
-	end_pfn = max_low_pfn;
-
-#ifdef CONFIG_X86_64
-	/*
-	 * There may be regions after the last E820_RAM region that we
-	 * want to include in the kernel direct mapping because their
-	 * contents are needed at runtime.
-	 */
-	if (efi_enabled) {
-		unsigned long efi_end;
-
-		efi_end = e820_end_pfn(MAXMEM>>PAGE_SHIFT, E820_RESERVED_EFI);
-		if (efi_end > end_pfn)
-			end_pfn = efi_end;
-	}
-#endif
-
-	max_low_pfn_mapped = init_memory_mapping(0, end_pfn << PAGE_SHIFT);
-	max_pfn_mapped = max_low_pfn_mapped;
+	/* max_low_pfn_mapped is updated here */
+	max_pfn_mapped = init_memory_mapping();
 
 #ifdef CONFIG_X86_64
 	if (max_pfn > max_low_pfn) {
-		max_pfn_mapped = init_memory_mapping(1UL<<32,
-						     max_pfn<<PAGE_SHIFT);
 		/* can we preseve max_low_pfn ?*/
 		max_low_pfn = max_pfn;
 	}
diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index 6cabf65..f1835e9 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -118,8 +118,8 @@ static int __meminit save_mr(struct map_range *mr, int nr_range,
  * This runs before bootmem is initialized and gets pages directly from
  * the physical memory. To access them they are temporarily mapped.
  */
-unsigned long __init_refok init_memory_mapping(unsigned long start,
-					       unsigned long end)
+unsigned long __init_refok __init_memory_mapping(unsigned long start,
+						 unsigned long end)
 {
 	unsigned long page_size_mask = 0;
 	unsigned long start_pfn, end_pfn;
@@ -301,6 +301,59 @@ unsigned long __init_refok init_memory_mapping(unsigned long start,
 	return ret >> PAGE_SHIFT;
 }
 
+/*
+ * Traverse the E820 memory map and add RAM/ACPI/EFI regions to the
+ * initial memory mapping.
+ */
+unsigned long __init_refok init_memory_mapping(void)
+{
+	struct e820entry *entry;
+	unsigned long last_pfn_mapped = 0;
+	unsigned long start, end;
+	int i;
+
+	/* Map the legacy region until we fix all drivers */
+	__init_memory_mapping(0, 1 << 20);
+
+	for (i = 0; i < e820.nr_map; i++) {
+		entry = &e820.map[i];
+		start = entry->addr;
+		end = start + entry->size;
+
+		/* We've already mapped below 1MB */
+		if (end < (1 << 20))
+			continue;
+
+		if (start < (1 << 20))
+			start = 1 << 20;
+#ifdef CONFIG_X86_32
+		/*
+		 * The map is sorted, so bail once we hit a region
+		 * that's above max_low_pfn.
+		 */
+		if (start >= max_low_pfn << PAGE_SHIFT)
+			break;
+
+		if (end > max_low_pfn << PAGE_SHIFT)
+			end = max_low_pfn << PAGE_SHIFT;
+#endif
+		switch (entry->type) {
+		case E820_RAM:
+		case E820_RESERVED_EFI:
+		case E820_ACPI:
+		case E820_NVS:
+			last_pfn_mapped = __init_memory_mapping(start, end);
+			break;
+		default:
+			continue;
+		}
+
+		if (end <= max_low_pfn << PAGE_SHIFT)
+			max_low_pfn_mapped = last_pfn_mapped;
+	}
+
+	return last_pfn_mapped;
+}
 
 /*
  * devmem_is_allowed() checks to see if /dev/mem access to a certain address
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 436a030..e86e370 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -659,7 +659,7 @@ int arch_add_memory(int nid, u64 start, u64 size)
 	unsigned long nr_pages = size >> PAGE_SHIFT;
 	int ret;
 
-	last_mapped_pfn = init_memory_mapping(start, start + size);
+	last_mapped_pfn = __init_memory_mapping(start, start + size);
 	if (last_mapped_pfn > max_pfn_mapped)
 		max_pfn_mapped = last_mapped_pfn;
 
diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index 264cc6e..ef0a725 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -573,8 +573,7 @@ void __init efi_init(void)
 		printk(KERN_WARNING
 		  "Kernel-defined memdesc doesn't match the one from EFI!\n");
 
-	if (add_efi_memmap)
-		do_add_efi_memmap();
+	do_add_efi_memmap();
 
 #ifdef CONFIG_X86_32
 	x86_platform.get_wallclock = efi_get_time;