[edk2-devel] [PATCH v3 2/2] UefiCpuPkg/PiSmmCpuDxeSmm: Change CR4.CET bit only

["Sheng Wei" <w.sheng@intel.com>]

Do not use fixed CR4 value 0x668, change CR4.CET bit only.

Signed-off-by: Sheng Wei <w.sheng@intel.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Wu Jiaxin <jiaxin.wu@intel.com>
Cc: Tan Dun <dun.tan@intel.com>
---
 UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmiEntry.nasm | 9 ++++++---
 UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmiEntry.nasm  | 3 ++-
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmiEntry.nasm b/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmiEntry.nasm
index 68332e2c3f..a087576a54 100644
--- a/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmiEntry.nasm
+++ b/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmiEntry.nasm
@@ -260,7 +260,8 @@ CetInterruptDone:
     bts     ecx, 16                     ; set WP
     mov     cr0, ecx
 
-    mov     eax, 0x668 | CR4_CET
+    mov     eax, cr4
+    bts     eax, CR4_CET_BIT
     mov     cr4, eax
 
     setssbsy
@@ -292,8 +293,10 @@ CetDone:
     xor     edx, edx
     wrmsr
 
-    mov     eax, 0x668
-    mov     cr4, eax       ; disable CET
+    ; clear CR4.CET bit
+    mov     eax, cr4
+    btr     eax, CR4_CET_BIT
+    mov     cr4, eax
 
     mov     ecx, MSR_IA32_PL0_SSP
     pop     eax
diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmiEntry.nasm b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmiEntry.nasm
index 007fbff640..7aed7c8dda 100644
--- a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmiEntry.nasm
+++ b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmiEntry.nasm
@@ -287,7 +287,8 @@ CetInterruptDone:
     bts     ecx, 16                     ; set WP
     mov     cr0, rcx
 
-    mov     eax, 0x668 | CR4_CET
+    mov     rax, cr4
+    bts     rax, CR4_CET_BIT
     mov     cr4, rax
 
     setssbsy
-- 
2.26.2.windows.1



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