-----Original Message-----
From: Ni, Ray <ray.ni@...>
Sent: Tuesday, August 11, 2020 4:04 PM
To: Gao, Zhichao <zhichao.gao@...>; devel@edk2.groups.io
Cc: Wang, Jian J <jian.j.wang@...>; Wu, Hao A <hao.a.wu@...>;
Gary Lin <glin@...>; Andrew Fish <afish@...>
Subject: RE: [PATCH 1/3] MdeModulePkg/PartitionDxe: Put the UDF check ahead
of MBR

Zhichao,
Can you also add notes in the commit message describing that for some ISOs
(better with more specific ISO info), the MBR information is not correct?

Thanks,
Ray

-----Original Message-----
From: Gao, Zhichao <zhichao.gao@...>
Sent: Tuesday, August 11, 2020 2:43 PM
To: devel@edk2.groups.io
Cc: Wang, Jian J <jian.j.wang@...>; Wu, Hao A
<hao.a.wu@...>; Ni, Ray <ray.ni@...>; Gary Lin
<glin@...>; Andrew Fish <afish@...>
Subject: [PATCH 1/3] MdeModulePkg/PartitionDxe: Put the UDF check
ahead of MBR

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=2823

Refer to UEFI spec 2.8, Section 13.3.2, a block device should be
scanned as below order:
1. GPT
2. ISO 9660 (El Torito) (UDF should aslo be here) 3. MBR 4. no
partition found
Note: UDF is using the same boot method as CD, so put it in the same
priority with ISO 9660.

This would also solve the issue that ISO image with MBR would be treat
as MBR device instead of CD/DVD. That would make the behavior of the
image boot different.

Cc: Jian J Wang <jian.j.wang@...>
Cc: Hao A Wu <hao.a.wu@...>
Cc: Ray Ni <ray.ni@...>
Cc: Gary Lin <glin@...>
Cc: Andrew Fish <afish@...>
Signed-off-by: Zhichao Gao <zhichao.gao@...>
---
MdeModulePkg/Universal/Disk/PartitionDxe/Partition.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/MdeModulePkg/Universal/Disk/PartitionDxe/Partition.c
b/MdeModulePkg/Universal/Disk/PartitionDxe/Partition.c
index 6a43c3cafb..473e091320 100644
--- a/MdeModulePkg/Universal/Disk/PartitionDxe/Partition.c
+++ b/MdeModulePkg/Universal/Disk/PartitionDxe/Partition.c
@@ -35,11 +35,19 @@ EFI_DRIVER_BINDING_PROTOCOL
gPartitionDriverBinding = {

//
// Prioritized function list to detect partition table.
+// Refer to UEFI Spec 13.3.2 Partition Discovery, the block device //
+should be scanned in below order:
+// 1. GPT
+// 2. ISO 9660 (El Torito) (or UDF)
+// 3. MBR
+// 4. no partiton found
+// Note: UDF is using a same method as booting from CD-ROM, so put it

along

+// with CD-ROM check.
//
PARTITION_DETECT_ROUTINE mPartitionDetectRoutineTable[] = {
PartitionInstallGptChildHandles,
- PartitionInstallMbrChildHandles,
PartitionInstallUdfChildHandles,
+ PartitionInstallMbrChildHandles,
NULL
};

--
2.21.0.windows.1