1 files changed, 9 insertions, 15 deletions

diff --git a/drivers/firmware/efi/libstub/x86-stub.c b/drivers/firmware/efi/libstub/x86-stub.c
index 05ccb229fb45..f0339b5d3658 100644
--- a/drivers/firmware/efi/libstub/x86-stub.c
+++ b/drivers/firmware/efi/libstub/x86-stub.c
@@ -606,24 +606,18 @@ static efi_status_t allocate_e820(struct boot_params *params,
 				  struct setup_data **e820ext,
 				  u32 *e820ext_size)
 {
-	unsigned long map_size, desc_size, buff_size;
-	struct efi_boot_memmap boot_map;
-	efi_memory_desc_t *map;
+	unsigned long map_size, desc_size, map_key;
 	efi_status_t status;
-	__u32 nr_desc;
+	__u32 nr_desc, desc_version;
 
-	boot_map.map		= ↦
-	boot_map.map_size	= &map_size;
-	boot_map.desc_size	= &desc_size;
-	boot_map.desc_ver	= NULL;
-	boot_map.key_ptr	= NULL;
-	boot_map.buff_size	= &buff_size;
+	/* Only need the size of the mem map and size of each mem descriptor */
+	map_size = 0;
+	status = efi_bs_call(get_memory_map, &map_size, NULL, &map_key,
+			     &desc_size, &desc_version);
+	if (status != EFI_BUFFER_TOO_SMALL)
+		return (status != EFI_SUCCESS) ? status : EFI_UNSUPPORTED;
 
-	status = efi_get_memory_map(&boot_map);
-	if (status != EFI_SUCCESS)
-		return status;
-
-	nr_desc = buff_size / desc_size;
+	nr_desc = map_size / desc_size + EFI_MMAP_NR_SLACK_SLOTS;
 
 	if (nr_desc > ARRAY_SIZE(params->e820_table)) {
 		u32 nr_e820ext = nr_desc - ARRAY_SIZE(params->e820_table);