From: Tom Lendacky <thomas.lendacky@amd.com>
BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=2198
SEV-ES guest AP boot support needs to transition from 64-bit long mode
into 16-bit real mode. This will require a 16-bit code segment descriptor.
Reserve one of the spare segment descriptors (0x28) for this purpose.
Cc: Jian J Wang <jian.j.wang@intel.com>
Cc: Hao A Wu <hao.a.wu@intel.com>
Cc: Dandan Bi <dandan.bi@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
MdeModulePkg/Core/DxeIplPeim/Ia32/DxeLoadFunc.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/MdeModulePkg/Core/DxeIplPeim/Ia32/DxeLoadFunc.c b/MdeModulePkg/Core/DxeIplPeim/Ia32/DxeLoadFunc.c
index 630a3503f6ba..b9af22bede61 100644
--- a/MdeModulePkg/Core/DxeIplPeim/Ia32/DxeLoadFunc.c
+++ b/MdeModulePkg/Core/DxeIplPeim/Ia32/DxeLoadFunc.c
@@ -33,7 +33,7 @@ GLOBAL_REMOVE_IF_UNREFERENCED IA32_GDT gGdtEntries[] = {
/* 0x10 */ {{0xffff, 0, 0, 0xf, 1, 0, 1, 0xf, 0, 0, 1, 1, 0}}, //linear code segment descriptor
/* 0x18 */ {{0xffff, 0, 0, 0x3, 1, 0, 1, 0xf, 0, 0, 1, 1, 0}}, //system data segment descriptor
/* 0x20 */ {{0xffff, 0, 0, 0xa, 1, 0, 1, 0xf, 0, 0, 1, 1, 0}}, //system code segment descriptor
-/* 0x28 */ {{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}}, //spare segment descriptor
+/* 0x28 */ {{0xffff, 0, 0, 0xa, 1, 0, 1, 0xf, 0, 0, 0, 1, 0}}, //system code16 segment descriptor
/* 0x30 */ {{0xffff, 0, 0, 0x2, 1, 0, 1, 0xf, 0, 0, 1, 1, 0}}, //system data segment descriptor
/* 0x38 */ {{0xffff, 0, 0, 0xa, 1, 0, 1, 0xf, 0, 1, 0, 1, 0}}, //system code segment descriptor
/* 0x40 */ {{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}}, //spare segment descriptor
--
2.17.1
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