Reviewed-by: Ray Ni
Thanks,
Ray
From: Tan, Dun
Sent: Friday, May 10, 2024 18:08
To: devel@edk2.groups.io
Cc: Ni, Ray ; Laszlo Ersek ; Kumar, Rahul
R ; Gerd Hoffmann ; Wu, Jiaxin
Subject: [PATCH 11/18] UefiCpuPkg: Disable PG in IA32 ApLoopCode
Disable paging in IA32 RelocateApLoop assembly
code to fix the issue that the AP page table is
unavailiable after boot OS under IA32 execution mode.
This issue exist in IA32 PEI + IA32 DXE normal boot
(also S3 boot with IA32 PEI after previous three commits
are accepted). In current MpLib code, the IA32 execution
mode code did not create page table in reserved memory
like what X64 code did. If PcdCpuStackGuard is TRUE, the
PG is enabled for AP in current RelocateApLoop assembly
code. And the page table for AP is unavailiable after
boot OS. This might cause potential issue. So disable PG
in IA32 RelocateApLoop.
Signed-off-by: Dun Tan
Cc: Ray Ni
Cc: Laszlo Ersek
Cc: Rahul Kumar
Cc: Gerd Hoffmann
Cc: Jiaxin Wu
---
UefiCpuPkg/Library/MpInitLib/Ia32/MpFuncs.nasm | 4
1 file changed, 4 insertions(+)
diff --git a/UefiCpuPkg/Library/MpInitLib/Ia32/MpFuncs.nasm
b/UefiCpuPkg/Library/MpInitLib/Ia32/MpFuncs.nasm
index d117f09ef5..75b18ce56f 100644
--- a/UefiCpuPkg/Library/MpInitLib/Ia32/MpFuncs.nasm
+++ b/UefiCpuPkg/Library/MpInitLib/Ia32/MpFuncs.nasm
@@ -225,6 +225,10 @@ RendezvousFunnelProcEnd:
; specific to SEV-ES support and are not applicable on IA32.
;-
AsmRelocateApLoopGenericStart:
+moveax, cr0
+btreax, 31 ; Clear CR0.PG
+movcr0, eax; Disable paging since the page table might
be unavailiable
+
moveax, esp
movesp, [eax + 12] ; TopOfApStack
push dword [eax] ; push return address for stack trace
--
2.31.1.windows.1
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