From 8a763b533bb1b10af2831f6c35d6545bdd5c69d1 Mon Sep 17 00:00:00 2001
From: Zhiguang Liu <zhiguang.liu@intel.com>
Date: Mon, 9 Jan 2023 11:34:22 +0800
Subject: MdeModulePkg: Disambiguate the meaning of PcdDxeIplSwitchToLongMode

Literally, the meaning of PcdDxeIplSwitchToLongMode is clear, indicating
whether need switch to long mode when loading DxeCore.
However, the comments in dec are confusing for the case where PEI core and
DXE core are both in 64-bit. This patch makes it clear.
PcdDxeIplSwitchToLongMode is true only when PEI core is 32-bit, and switch
to long mode to load 64-bit DXE core. In other cases, this PCD is false.
This also aligns with current usage in OvmfPkg.

Cc: Jian J Wang <jian.j.wang@intel.com>
Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Ray Ni <ray.ni@intel.com>
Signed-off-by: Zhiguang Liu <zhiguang.liu@intel.com>
Reviewed-by: Liming Gao <gaoliming@byosoft.com.cn>
Reviewed-by: Ray Ni <ray.ni@intel.com>
---
 MdeModulePkg/MdeModulePkg.dec | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/MdeModulePkg/MdeModulePkg.dec b/MdeModulePkg/MdeModulePkg.dec
index 9605c617b7..e8058c8bfa 100644
--- a/MdeModulePkg/MdeModulePkg.dec
+++ b/MdeModulePkg/MdeModulePkg.dec
@@ -927,10 +927,8 @@
 
 [PcdsFeatureFlag.IA32, PcdsFeatureFlag.X64]
   ## Indicates if DxeIpl should switch to long mode to enter DXE phase.
-  #  It is assumed that 64-bit DxeCore is built in firmware if it is true; otherwise 32-bit DxeCore
-  #  is built in firmware.<BR><BR>
   #   TRUE  - DxeIpl will load a 64-bit DxeCore and switch to long mode to hand over to DxeCore.<BR>
-  #   FALSE - DxeIpl will load a 32-bit DxeCore and perform stack switch to hand over to DxeCore.<BR>
+  #   FALSE - DxeIpl will load a 32-bit or 64-bit DxeCore and perform stack switch to hand over to DxeCore.<BR>
   # @Prompt DxeIpl switch to long mode.
   gEfiMdeModulePkgTokenSpaceGuid.PcdDxeIplSwitchToLongMode|TRUE|BOOLEAN|0x0001003b
 
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