[edk2-devel] [PATCH] UefiCpuPkg/CpuExceptionHandlerLib: Fix #AC split lock

[John E Lofgren]

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=2150

Fix #AC split lock's caused by seperating base and limit
from sgdt and sidt by changing xchg operands to 32-bit to
stop from crossing cacheline.

Signed-off-by: John E Lofgren <john.e.lofgren at intel.com>
---
 UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ExceptionHandlerAsm.nasm | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ExceptionHandlerAsm.nasm b/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ExceptionHandlerAsm.nasm
index 4db1a09f28..6d83dca4b9 100644
--- a/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ExceptionHandlerAsm.nasm
+++ b/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ExceptionHandlerAsm.nasm
@@ -184,17 +184,17 @@ HasErrorCode:
     push    rax
     push    rax
     sidt    [rsp]
-    xchg    rax, [rsp + 2]
-    xchg    rax, [rsp]
-    xchg    rax, [rsp + 8]
+    xchg    eax, [rsp + 2]
+    xchg    eax, [rsp]
+    xchg    eax, [rsp + 8]
 
     xor     rax, rax
     push    rax
     push    rax
     sgdt    [rsp]
-    xchg    rax, [rsp + 2]
-    xchg    rax, [rsp]
-    xchg    rax, [rsp + 8]
+    xchg    eax, [rsp + 2]
+    xchg    eax, [rsp]
+    xchg    eax, [rsp + 8]
 
 ;; UINT64  Ldtr, Tr;
     xor     rax, rax
-- 
2.16.2.windows.1


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