x86, efi: Break up large initrd reads

The efi boot stub tries to read the entire initrd in 1 go, however
some efi implementations hang if too much if asked to read too much
data at the same time. After some experimentation I found out that my
asrock p67 board will hang if asked to read chunks of 4MiB, so use a
safe value.

elilo reads in chunks of 16KiB, but since that requires many read
calls I use a value of 1 MiB.  hpa suggested adding individual
blacklists for when systems are found where this value causes a crash.

Signed-off-by: Maarten Lankhorst <m.b.lankhorst@gmail.com>
Link: http://lkml.kernel.org/r/4EEB3A02.3090201@gmail.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

arch/x86/boot/compressed/eboot.c

@@ -643,14 +643,22 @@ static efi_status_t handle_ramdisks(efi_loaded_image_t *image,
 			u64 size;
 
 			size = initrds[j].size;
-			status = efi_call_phys3(fh->read, initrds[j].handle,
-						&size, addr);
-			if (status != EFI_SUCCESS)
-				goto free_initrd_total;
+			while (size) {
+				u64 chunksize;
+				if (size > EFI_READ_CHUNK_SIZE)
+					chunksize = EFI_READ_CHUNK_SIZE;
+				else
+					chunksize = size;
+				status = efi_call_phys3(fh->read,
+							initrds[j].handle,
+							&chunksize, addr);
+				if (status != EFI_SUCCESS)
+					goto free_initrd_total;
+				addr += chunksize;
+				size -= chunksize;
+			}
 
 			efi_call_phys1(fh->close, initrds[j].handle);
-
-			addr += size;
 		}
 
 	}

arch/x86/boot/compressed/eboot.h

@@ -12,6 +12,7 @@
 #define DESC_TYPE_CODE_DATA	(1 << 0)
 
 #define EFI_PAGE_SIZE		(1UL << EFI_PAGE_SHIFT)
+#define EFI_READ_CHUNK_SIZE	(1024 * 1024)
 
 #define PIXEL_RGB_RESERVED_8BIT_PER_COLOR		0
 #define PIXEL_BGR_RESERVED_8BIT_PER_COLOR		1