[PATCH v13 11/46] UefiCpuPkg/CpuExceptionHandler: Add base support for the #VC exception

["Lendacky, Thomas" <thomas.lendacky@amd.com>]

From: Tom Lendacky <thomas.lendacky@amd.com>

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=2198

Add base support to handle #VC exceptions. Update the common exception
handlers to invoke the VmgExitHandleVc () function of the VmgExitLib
library when a #VC is encountered. A non-zero return code will propagate
to the targeted exception handler.

Under SEV-ES, a DR7 read or write intercept generates a #VC exception.
To avoid exception recursion, a #VC exception will not try to read and
push the actual debug registers into the EFI_SYSTEM_CONTEXT_X64 struct
and instead push zeroes. The #VC exception handler does not make use of
the debug registers from the saved context and the exception processing
exit code does not attempt to restore the debug register values.

Cc: Eric Dong <eric.dong@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Eric Dong <eric.dong@intel.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
 .../DxeCpuExceptionHandlerLib.inf             |  1 +
 .../PeiCpuExceptionHandlerLib.inf             |  1 +
 .../SecPeiCpuExceptionHandlerLib.inf          |  1 +
 .../SmmCpuExceptionHandlerLib.inf             |  1 +
 .../Xcode5SecPeiCpuExceptionHandlerLib.inf    |  1 +
 .../CpuExceptionCommon.c                      | 10 +++++++++-
 .../PeiDxeSmmCpuException.c                   | 20 ++++++++++++++++++-
 .../SecPeiCpuException.c                      | 19 ++++++++++++++++++
 .../X64/ExceptionHandlerAsm.nasm              | 17 ++++++++++++++++
 .../X64/Xcode5ExceptionHandlerAsm.nasm        | 17 ++++++++++++++++
 10 files changed, 86 insertions(+), 2 deletions(-)

diff --git a/UefiCpuPkg/Library/CpuExceptionHandlerLib/DxeCpuExceptionHandlerLib.inf b/UefiCpuPkg/Library/CpuExceptionHandlerLib/DxeCpuExceptionHandlerLib.inf
index 61e2ec30b089..07b34c92a892 100644
--- a/UefiCpuPkg/Library/CpuExceptionHandlerLib/DxeCpuExceptionHandlerLib.inf
+++ b/UefiCpuPkg/Library/CpuExceptionHandlerLib/DxeCpuExceptionHandlerLib.inf
@@ -57,3 +57,4 @@ [LibraryClasses]
   PeCoffGetEntryPointLib
   MemoryAllocationLib
   DebugLib
+  VmgExitLib
diff --git a/UefiCpuPkg/Library/CpuExceptionHandlerLib/PeiCpuExceptionHandlerLib.inf b/UefiCpuPkg/Library/CpuExceptionHandlerLib/PeiCpuExceptionHandlerLib.inf
index 093374944df6..feae7b3e06de 100644
--- a/UefiCpuPkg/Library/CpuExceptionHandlerLib/PeiCpuExceptionHandlerLib.inf
+++ b/UefiCpuPkg/Library/CpuExceptionHandlerLib/PeiCpuExceptionHandlerLib.inf
@@ -52,6 +52,7 @@ [LibraryClasses]
   HobLib
   MemoryAllocationLib
   SynchronizationLib
+  VmgExitLib
 
 [Pcd]
   gEfiMdeModulePkgTokenSpaceGuid.PcdCpuStackGuard    # CONSUMES
diff --git a/UefiCpuPkg/Library/CpuExceptionHandlerLib/SecPeiCpuExceptionHandlerLib.inf b/UefiCpuPkg/Library/CpuExceptionHandlerLib/SecPeiCpuExceptionHandlerLib.inf
index 6d25cafe2ca3..967cb61ba6d9 100644
--- a/UefiCpuPkg/Library/CpuExceptionHandlerLib/SecPeiCpuExceptionHandlerLib.inf
+++ b/UefiCpuPkg/Library/CpuExceptionHandlerLib/SecPeiCpuExceptionHandlerLib.inf
@@ -48,3 +48,4 @@ [LibraryClasses]
   PrintLib
   LocalApicLib
   PeCoffGetEntryPointLib
+  VmgExitLib
diff --git a/UefiCpuPkg/Library/CpuExceptionHandlerLib/SmmCpuExceptionHandlerLib.inf b/UefiCpuPkg/Library/CpuExceptionHandlerLib/SmmCpuExceptionHandlerLib.inf
index 2ffbbccc302f..4cdb11c04ea0 100644
--- a/UefiCpuPkg/Library/CpuExceptionHandlerLib/SmmCpuExceptionHandlerLib.inf
+++ b/UefiCpuPkg/Library/CpuExceptionHandlerLib/SmmCpuExceptionHandlerLib.inf
@@ -51,4 +51,5 @@ [LibraryClasses]
   LocalApicLib
   PeCoffGetEntryPointLib
   DebugLib
+  VmgExitLib
 
diff --git a/UefiCpuPkg/Library/CpuExceptionHandlerLib/Xcode5SecPeiCpuExceptionHandlerLib.inf b/UefiCpuPkg/Library/CpuExceptionHandlerLib/Xcode5SecPeiCpuExceptionHandlerLib.inf
index 7e21beaab6f2..743c2aa76684 100644
--- a/UefiCpuPkg/Library/CpuExceptionHandlerLib/Xcode5SecPeiCpuExceptionHandlerLib.inf
+++ b/UefiCpuPkg/Library/CpuExceptionHandlerLib/Xcode5SecPeiCpuExceptionHandlerLib.inf
@@ -53,3 +53,4 @@ [LibraryClasses]
   PrintLib
   LocalApicLib
   PeCoffGetEntryPointLib
+  VmgExitLib
diff --git a/UefiCpuPkg/Library/CpuExceptionHandlerLib/CpuExceptionCommon.c b/UefiCpuPkg/Library/CpuExceptionHandlerLib/CpuExceptionCommon.c
index 8adbd43fefb4..c9003b10e552 100644
--- a/UefiCpuPkg/Library/CpuExceptionHandlerLib/CpuExceptionCommon.c
+++ b/UefiCpuPkg/Library/CpuExceptionHandlerLib/CpuExceptionCommon.c
@@ -14,7 +14,7 @@
 //
 // 1 means an error code will be pushed, otherwise 0
 //
-CONST UINT32 mErrorCodeFlag = 0x00227d00;
+CONST UINT32 mErrorCodeFlag = 0x20227d00;
 
 //
 // Define the maximum message length
@@ -45,6 +45,14 @@ CONST CHAR8 *mExceptionNameStr[] = {
   "#XM - SIMD floating-point",
   "#VE - Virtualization",
   "#CP - Control Protection"
+  "Reserved",
+  "Reserved",
+  "Reserved",
+  "Reserved",
+  "Reserved",
+  "Reserved",
+  "Reserved",
+  "#VC - VMM Communication",
 };
 
 #define EXCEPTION_KNOWN_NAME_NUM  (sizeof (mExceptionNameStr) / sizeof (CHAR8 *))
diff --git a/UefiCpuPkg/Library/CpuExceptionHandlerLib/PeiDxeSmmCpuException.c b/UefiCpuPkg/Library/CpuExceptionHandlerLib/PeiDxeSmmCpuException.c
index 6a2670d55918..892d349d4b37 100644
--- a/UefiCpuPkg/Library/CpuExceptionHandlerLib/PeiDxeSmmCpuException.c
+++ b/UefiCpuPkg/Library/CpuExceptionHandlerLib/PeiDxeSmmCpuException.c
@@ -6,8 +6,9 @@ SPDX-License-Identifier: BSD-2-Clause-Patent
 
 **/
 
-#include "CpuExceptionCommon.h"
 #include <Library/DebugLib.h>
+#include <Library/VmgExitLib.h>
+#include "CpuExceptionCommon.h"
 
 /**
   Internal worker function for common exception handler.
@@ -27,6 +28,23 @@ CommonExceptionHandlerWorker (
   RESERVED_VECTORS_DATA          *ReservedVectors;
   EFI_CPU_INTERRUPT_HANDLER      *ExternalInterruptHandler;
 
+  if (ExceptionType == VC_EXCEPTION) {
+    EFI_STATUS  Status;
+    //
+    // #VC needs to be handled immediately upon enabling exception handling
+    // and therefore can't use the RegisterCpuInterruptHandler() interface.
+    //
+    // Handle the #VC:
+    //   On EFI_SUCCESS - Exception has been handled, return
+    //   On other       - ExceptionType contains (possibly new) exception
+    //                    value
+    //
+    Status = VmgExitHandleVc (&ExceptionType, SystemContext);
+    if (!EFI_ERROR (Status)) {
+      return;
+    }
+  }
+
   ExceptionHandlerContext  = (EXCEPTION_HANDLER_CONTEXT *) (UINTN) (SystemContext.SystemContextIa32);
   ReservedVectors          = ExceptionHandlerData->ReservedVectors;
   ExternalInterruptHandler = ExceptionHandlerData->ExternalInterruptHandler;
diff --git a/UefiCpuPkg/Library/CpuExceptionHandlerLib/SecPeiCpuException.c b/UefiCpuPkg/Library/CpuExceptionHandlerLib/SecPeiCpuException.c
index d4ae153c5742..01b5a2f1f4fc 100644
--- a/UefiCpuPkg/Library/CpuExceptionHandlerLib/SecPeiCpuException.c
+++ b/UefiCpuPkg/Library/CpuExceptionHandlerLib/SecPeiCpuException.c
@@ -7,6 +7,7 @@ SPDX-License-Identifier: BSD-2-Clause-Patent
 **/
 
 #include <PiPei.h>
+#include <Library/VmgExitLib.h>
 #include "CpuExceptionCommon.h"
 
 CONST UINTN    mDoFarReturnFlag  = 0;
@@ -24,6 +25,24 @@ CommonExceptionHandler (
   IN EFI_SYSTEM_CONTEXT   SystemContext
   )
 {
+  if (ExceptionType == VC_EXCEPTION) {
+    EFI_STATUS  Status;
+    //
+    // #VC needs to be handled immediately upon enabling exception handling
+    // and therefore can't use the RegisterCpuInterruptHandler() interface
+    // (which isn't supported under Sec and Pei anyway).
+    //
+    // Handle the #VC:
+    //   On EFI_SUCCESS - Exception has been handled, return
+    //   On other       - ExceptionType contains (possibly new) exception
+    //                    value
+    //
+    Status = VmgExitHandleVc (&ExceptionType, SystemContext);
+    if (!EFI_ERROR (Status)) {
+      return;
+    }
+  }
+
   //
   // Initialize the serial port before dumping.
   //
diff --git a/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ExceptionHandlerAsm.nasm b/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ExceptionHandlerAsm.nasm
index 3814f9de3703..2a5545ecfd41 100644
--- a/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ExceptionHandlerAsm.nasm
+++ b/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ExceptionHandlerAsm.nasm
@@ -18,6 +18,8 @@
 ; CommonExceptionHandler()
 ;
 
+%define VC_EXCEPTION 29
+
 extern ASM_PFX(mErrorCodeFlag)    ; Error code flags for exceptions
 extern ASM_PFX(mDoFarReturnFlag)  ; Do far return flag
 extern ASM_PFX(CommonExceptionHandler)
@@ -224,6 +226,9 @@ HasErrorCode:
     push    rax
 
 ;; UINT64  Dr0, Dr1, Dr2, Dr3, Dr6, Dr7;
+    cmp     qword [rbp + 8], VC_EXCEPTION
+    je      VcDebugRegs          ; For SEV-ES (#VC) Debug registers ignored
+
     mov     rax, dr7
     push    rax
     mov     rax, dr6
@@ -236,7 +241,19 @@ HasErrorCode:
     push    rax
     mov     rax, dr0
     push    rax
+    jmp     DrFinish
 
+VcDebugRegs:
+;; UINT64  Dr0, Dr1, Dr2, Dr3, Dr6, Dr7 are skipped for #VC to avoid exception recursion
+    xor     rax, rax
+    push    rax
+    push    rax
+    push    rax
+    push    rax
+    push    rax
+    push    rax
+
+DrFinish:
 ;; FX_SAVE_STATE_X64 FxSaveState;
     sub rsp, 512
     mov rdi, rsp
diff --git a/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/Xcode5ExceptionHandlerAsm.nasm b/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/Xcode5ExceptionHandlerAsm.nasm
index 19198f273137..26cae56cc5cf 100644
--- a/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/Xcode5ExceptionHandlerAsm.nasm
+++ b/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/Xcode5ExceptionHandlerAsm.nasm
@@ -18,6 +18,8 @@
 ; CommonExceptionHandler()
 ;
 
+%define VC_EXCEPTION 29
+
 extern ASM_PFX(mErrorCodeFlag)    ; Error code flags for exceptions
 extern ASM_PFX(mDoFarReturnFlag)  ; Do far return flag
 extern ASM_PFX(CommonExceptionHandler)
@@ -225,6 +227,9 @@ HasErrorCode:
     push    rax
 
 ;; UINT64  Dr0, Dr1, Dr2, Dr3, Dr6, Dr7;
+    cmp     qword [rbp + 8], VC_EXCEPTION
+    je      VcDebugRegs          ; For SEV-ES (#VC) Debug registers ignored
+
     mov     rax, dr7
     push    rax
     mov     rax, dr6
@@ -237,7 +242,19 @@ HasErrorCode:
     push    rax
     mov     rax, dr0
     push    rax
+    jmp     DrFinish
 
+VcDebugRegs:
+;; UINT64  Dr0, Dr1, Dr2, Dr3, Dr6, Dr7 are skipped for #VC to avoid exception recursion
+    xor     rax, rax
+    push    rax
+    push    rax
+    push    rax
+    push    rax
+    push    rax
+    push    rax
+
+DrFinish:
 ;; FX_SAVE_STATE_X64 FxSaveState;
     sub rsp, 512
     mov rdi, rsp
-- 
2.27.0