@@ -1,6 +1,7 @@
 #ifndef _ASM_EFI_H
 #define _ASM_EFI_H
 
+#include <asm/boot.h>
 #include <asm/cpufeature.h>
 #include <asm/io.h>
 #include <asm/mmu_context.h>

@@ -206,6 +206,10 @@ static efi_status_t exit_boot_func(efi_system_table_t *sys_table_arg,
 	return update_fdt_memmap(p->new_fdt_addr, map);
 }
 
+#ifndef MAX_FDT_SIZE
+#define MAX_FDT_SIZE	SZ_2M
+#endif
+
 /*
  * Allocate memory for a new FDT, then add EFI, commandline, and
  * initrd related fields to the FDT.  This routine increases the

@@ -233,7 +237,6 @@ efi_status_t allocate_new_fdt_and_exit_boot(efi_system_table_t *sys_table,
 	u32 desc_ver;
 	unsigned long mmap_key;
 	efi_memory_desc_t *memory_map, *runtime_map;
-	unsigned long new_fdt_size;
 	efi_status_t status;
 	int runtime_entry_count = 0;
 	struct efi_boot_memmap map;

@@ -262,41 +265,29 @@ efi_status_t allocate_new_fdt_and_exit_boot(efi_system_table_t *sys_table,
 	       "Exiting boot services and installing virtual address map...\n");
 
 	map.map = &memory_map;
+	status = efi_high_alloc(sys_table, MAX_FDT_SIZE, EFI_FDT_ALIGN,
+				new_fdt_addr, max_addr);
+	if (status != EFI_SUCCESS) {
+		pr_efi_err(sys_table,
+			   "Unable to allocate memory for new device tree.\n");
+		goto fail;
+	}
+
 	/*
-	 * Estimate size of new FDT, and allocate memory for it. We
-	 * will allocate a bigger buffer if this ends up being too
-	 * small, so a rough guess is OK here.
+	 * Now that we have done our final memory allocation (and free)
+	 * we can get the memory map key needed for exit_boot_services().
 	 */
-	new_fdt_size = fdt_size + EFI_PAGE_SIZE;
-	while (1) {
-		status = efi_high_alloc(sys_table, new_fdt_size, EFI_FDT_ALIGN,
-					new_fdt_addr, max_addr);
-		if (status != EFI_SUCCESS) {
-			pr_efi_err(sys_table, "Unable to allocate memory for new device tree.\n");
-			goto fail;
-		}
-
-		status = update_fdt(sys_table,
-				    (void *)fdt_addr, fdt_size,
-				    (void *)*new_fdt_addr, new_fdt_size,
-				    cmdline_ptr, initrd_addr, initrd_size);
+	status = efi_get_memory_map(sys_table, &map);
+	if (status != EFI_SUCCESS)
+		goto fail_free_new_fdt;
 
-		/* Succeeding the first time is the expected case. */
-		if (status == EFI_SUCCESS)
-			break;
+	status = update_fdt(sys_table, (void *)fdt_addr, fdt_size,
+			    (void *)*new_fdt_addr, MAX_FDT_SIZE, cmdline_ptr,
+			    initrd_addr, initrd_size);
 
-		if (status == EFI_BUFFER_TOO_SMALL) {
-			/*
-			 * We need to allocate more space for the new
-			 * device tree, so free existing buffer that is
-			 * too small.
-			 */
-			efi_free(sys_table, new_fdt_size, *new_fdt_addr);
-			new_fdt_size += EFI_PAGE_SIZE;
-		} else {
-			pr_efi_err(sys_table, "Unable to construct new device tree.\n");
-			goto fail_free_new_fdt;
-		}
+	if (status != EFI_SUCCESS) {
+		pr_efi_err(sys_table, "Unable to construct new device tree.\n");
+		goto fail_free_new_fdt;
 	}
 
 	priv.runtime_map = runtime_map;

@@ -340,7 +331,7 @@ efi_status_t allocate_new_fdt_and_exit_boot(efi_system_table_t *sys_table,
 	pr_efi_err(sys_table, "Exit boot services failed.\n");
 
 fail_free_new_fdt:
-	efi_free(sys_table, new_fdt_size, *new_fdt_addr);
+	efi_free(sys_table, MAX_FDT_SIZE, *new_fdt_addr);
 
 fail:
 	sys_table->boottime->free_pool(runtime_map);