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

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

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 4mb, so use a safe value.

>From elilo source code:
/*
 * We load by chunks rather than a single big read because
 * early versions of EFI had troubles loading files
 * from floppies in a single big request.  Breaking
 * the read down into chunks of 4KB fixed that
 * problem. While this problem has been fixed, we still prefer
 * this method because it tells us whether or not we're making
 * forward progress.
 */

While the comment says 4KB, it's using 4 * EFI_PAGE_SIZE (16KB),
so I went by the safest route of following elilo here.

Signed-off-by: Maarten Lankhorst <m.b.lankhorst@gmail.com>
---
 arch/x86/boot/compressed/eboot.c |   20 ++++++++++++++------
 1 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c
index 8627a56..a26be50 100644
--- a/arch/x86/boot/compressed/eboot.c
+++ b/arch/x86/boot/compressed/eboot.c
@@ -695,14 +695,22 @@ 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 > 4 * EFI_PAGE_SIZE)
+					chunksize = 4 * EFI_PAGE_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;
 		}
 
 	}
-- 
1.7.7.1