[PATCH v2] x86, efi: Break up large initrd reads

[Maarten Lankhorst <m.b.lankhorst@gmail.com>]

[PATCH 11/11] 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>
---

v2: Bump read size to 1 MiB, and use a #define for chunk size

 arch/x86/boot/compressed/eboot.c |   21 +++++++++++++++------
 1 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c
index 8627a56..df4f552 100644
--- a/arch/x86/boot/compressed/eboot.c
+++ b/arch/x86/boot/compressed/eboot.c
@@ -23,6 +23,7 @@
 #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
@@ -695,14 +696,22 @@ grow:
 			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;
 		}
 
 	}
-- 
1.7.7.4