From 48f5f4f66714aa115c685f119710238da66ac15e Mon Sep 17 00:00:00 2001
From: Mikhail Krichanov <mikhailkrichanov@gmail.com>
Date: Fri, 27 Sep 2024 15:43:46 +0300
Subject: [PATCH] Ring3: Fixed buggy timer interrupt handling for AARCH64.

---
 ArmPkg/Library/ArmExceptionLib/AArch64/ExceptionSupport.S | 2 +-
 ArmPkg/Library/ArmExceptionLib/ArmExceptionLib.c          | 3 +++
 MdeModulePkg/Core/Dxe/SysCall/AARCH64/CoreBootServices.S  | 6 ------
 3 files changed, 4 insertions(+), 7 deletions(-)

diff --git a/ArmPkg/Library/ArmExceptionLib/AArch64/ExceptionSupport.S b/ArmPkg/Library/ArmExceptionLib/AArch64/ExceptionSupport.S
index 2de7be7c8b..687d22e852 100644
--- a/ArmPkg/Library/ArmExceptionLib/AArch64/ExceptionSupport.S
+++ b/ArmPkg/Library/ArmExceptionLib/AArch64/ExceptionSupport.S
@@ -294,7 +294,7 @@ ASM_PFX(CommonExceptionEntry):
   ldp      x24, x25, [sp, #0xc0]
   ldp      x26, x27, [sp, #0xd0]
   // Preserve return value for SVC.
-  mrs      x1, esr_el1
+  ldr      x1, [x28, #(FP_CONTEXT_SIZE + 0x18)] // Exception syndrome register
   lsr      x1, x1, #26
   and      x1, x1, #0x3F
   cmp      x1, #0x15
diff --git a/ArmPkg/Library/ArmExceptionLib/ArmExceptionLib.c b/ArmPkg/Library/ArmExceptionLib/ArmExceptionLib.c
index 83d5543df3..1efb7f5c94 100644
--- a/ArmPkg/Library/ArmExceptionLib/ArmExceptionLib.c
+++ b/ArmPkg/Library/ArmExceptionLib/ArmExceptionLib.c
@@ -141,6 +141,9 @@ CommonCExceptionHandler (
   if ((UINTN)ExceptionType <= gMaxExceptionNumber) {
     if (gExceptionHandlers[ExceptionType]) {
       gExceptionHandlers[ExceptionType](ExceptionType, SystemContext);
+#if defined (MDE_CPU_AARCH64)
+      SystemContext.SystemContextAArch64->ESR = 0;
+#endif
       return EFI_SUCCESS;
     }
   } else {
diff --git a/MdeModulePkg/Core/Dxe/SysCall/AARCH64/CoreBootServices.S b/MdeModulePkg/Core/Dxe/SysCall/AARCH64/CoreBootServices.S
index 1192c150de..8307e93392 100644
--- a/MdeModulePkg/Core/Dxe/SysCall/AARCH64/CoreBootServices.S
+++ b/MdeModulePkg/Core/Dxe/SysCall/AARCH64/CoreBootServices.S
@@ -107,7 +107,6 @@ ASM_FUNC(ArmCallRing3)
   //
   msr  spsr_el1, x1
   isb
-  dsb  sy
   eret
 
 //------------------------------------------------------------------------------
@@ -119,11 +118,6 @@ ASM_FUNC(ArmCallRing3)
 //   );
 //------------------------------------------------------------------------------
 ASM_FUNC(ReturnToCore)
-  // Zero Exception Syndrome Register to prevent QEMU from random crashing.
-  msr  esr_el1, xzr
-  msr  spsr_el1, xzr
-  msr  elr_el1, xzr
-  msr  far_el1, xzr
   // Switch to Core Stack.
   mov  sp, x1
   // Restore registers and Stack.