efi: fix allocation problems if ExitBootServices() fails

If calling ExitBootServices() fails, the required memory map size may
have increased. When initially allocating the memory map, allocate a
slightly larger buffer (by an arbitrary 8 entries) to fix this.

The ARM code path was already allocating a larger buffer than required,
so this moves the code to be common for all architectures.

This was seen on the following machine when using the iscsidxe UEFI
driver. The machine would consistently fail the first call to
ExitBootServices().
System Information
        Manufacturer: Supermicro
        Product Name: X10SLE-F/HF
BIOS Information
        Vendor: American Megatrends Inc.
        Version: 2.00
        Release Date: 04/24/2014

Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Roy Franz <roy.franz@linaro.org>
Acked-by: Ian Campbell <ian.campbell@citrix.com>

xen/arch/arm/efi/efi-boot.h

@@ -370,16 +370,14 @@ static void __init efi_arch_cfg_file_late(EFI_FILE_HANDLE dir_handle, char *sect
 {
 }
 
-static void *__init efi_arch_allocate_mmap_buffer(UINTN *map_size)
+static void *__init efi_arch_allocate_mmap_buffer(UINTN map_size)
 {
     void *ptr;
     EFI_STATUS status;
-    UINTN map_size_alloc = *map_size + EFI_PAGE_SIZE;
 
-    status = efi_bs->AllocatePool(EfiLoaderData, map_size_alloc, &ptr);
+    status = efi_bs->AllocatePool(EfiLoaderData, map_size, &ptr);
     if ( status != EFI_SUCCESS )
         return NULL;
-    *map_size = map_size_alloc;
     return ptr;
 }
 

xen/arch/x86/efi/efi-boot.h

@@ -190,10 +190,10 @@ static void __init efi_arch_process_memory_map(EFI_SYSTEM_TABLE *SystemTable,
 
 }
 
-static void *__init efi_arch_allocate_mmap_buffer(UINTN *map_size)
+static void *__init efi_arch_allocate_mmap_buffer(UINTN map_size)
 {
     place_string(&mbi.mem_upper, NULL);
-    mbi.mem_upper -= *map_size;
+    mbi.mem_upper -= map_size;
     mbi.mem_upper &= -__alignof__(EFI_MEMORY_DESCRIPTOR);
     if ( mbi.mem_upper < xen_phys_start )
         return NULL;

xen/common/efi/boot.c

@@ -700,7 +700,7 @@ efi_start(EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE *SystemTable)
     EFI_STATUS status;
     unsigned int i, argc;
     CHAR16 **argv, *file_name, *cfg_file_name = NULL, *options = NULL;
-    UINTN map_key, info_size, gop_mode = ~0;
+    UINTN map_alloc_size, map_key, info_size, gop_mode = ~0;
     EFI_HANDLE *handles = NULL;
     EFI_SHIM_LOCK_PROTOCOL *shim_lock;
     EFI_GRAPHICS_OUTPUT_PROTOCOL *gop = NULL;
@@ -1053,14 +1053,16 @@ efi_start(EFI_HANDLE ImageHandle, EFI_SYSTEM_TABLE *SystemTable)
             efi_arch_video_init(gop, info_size, mode_info);
     }
 
-    efi_bs->GetMemoryMap(&efi_memmap_size, NULL, &map_key,
+    efi_bs->GetMemoryMap(&map_alloc_size, NULL, &map_key,
                          &efi_mdesc_size, &mdesc_ver);
-    efi_memmap = efi_arch_allocate_mmap_buffer(&efi_memmap_size);
+    map_alloc_size += 8 * efi_mdesc_size;
+    efi_memmap = efi_arch_allocate_mmap_buffer(map_alloc_size);
     if ( !efi_memmap )
         blexit(L"Unable to allocate memory for EFI memory map");
 
     for ( retry = 0; ; retry = 1 )
     {
+        efi_memmap_size = map_alloc_size;
         status = efi_bs->GetMemoryMap(&efi_memmap_size, efi_memmap, &map_key,
                                       &efi_mdesc_size, &mdesc_ver);
         if ( EFI_ERROR(status) )