From b1db09657546f4983a1ec18336b36212b5875c3f Mon Sep 17 00:00:00 2001
From: "Xie, Yuanhao" <yuanhao.xie@intel.com>
Date: Tue, 21 Mar 2023 15:29:59 +0800
Subject: [PATCH] UefiCpuPkg: Solve that stack top address is not mapped in
 pagetable

For the case CPU logic index is 0, RSP points to the very top of all AP
stacks. That address is not mapped in page table.

Cc: Guo Dong <guo.dong@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Sean Rhodes <sean@starlabs.systems>
Cc: James Lu <james.lu@intel.com>
Cc: Gua Guo <gua.guo@intel.com>
Signed-off-by: Ted Kuo <ted.kuo@intel.com>
Reviewed-by: Ray Ni <ray.ni@intel.com>
---
 UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm | 1 +
 1 file changed, 1 insertion(+)

diff --git a/UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm b/UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm
index 9ebe31795b..5bcdf7726b 100644
--- a/UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm
+++ b/UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm
@@ -315,6 +315,7 @@ MwaitCheckGeneric:
 MwaitLoopGeneric:
     cli
     mov        rax, rsp           ; Set Monitor Address
+    sub        eax, 8             ; To ensure the monitor address is in the page table
     xor        ecx, ecx           ; ecx = 0
     xor        edx, edx           ; edx = 0
     monitor