UefiCpuPkg/CpuExceptionHandler: Add base support for the #VC exception

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>
Regression-tested-by: Laszlo Ersek <lersek@redhat.com>

10 files changed, 86 insertions, 2 deletions

diff --git a/UefiCpuPkg/Library/CpuExceptionHandlerLib/CpuExceptionCommon.c b/UefiCpuPkg/Library/CpuExceptionHandlerLib/CpuExceptionCommon.c
index 8adbd43fef..c9003b10e5 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/DxeCpuExceptionHandlerLib.inf b/UefiCpuPkg/Library/CpuExceptionHandlerLib/DxeCpuExceptionHandlerLib.inf
index 61e2ec30b0..07b34c92a8 100644
--- a/UefiCpuPkg/Library/CpuExceptionHandlerLib/DxeCpuExceptionHandlerLib.inf
+++ b/UefiCpuPkg/Library/CpuExceptionHandlerLib/DxeCpuExceptionHandlerLib.inf
@@ -57,3 +57,4 @@
   PeCoffGetEntryPointLib

   MemoryAllocationLib

   DebugLib

+  VmgExitLib

diff --git a/UefiCpuPkg/Library/CpuExceptionHandlerLib/PeiCpuExceptionHandlerLib.inf b/UefiCpuPkg/Library/CpuExceptionHandlerLib/PeiCpuExceptionHandlerLib.inf
index 093374944d..feae7b3e06 100644
--- a/UefiCpuPkg/Library/CpuExceptionHandlerLib/PeiCpuExceptionHandlerLib.inf
+++ b/UefiCpuPkg/Library/CpuExceptionHandlerLib/PeiCpuExceptionHandlerLib.inf
@@ -52,6 +52,7 @@
   HobLib

   MemoryAllocationLib

   SynchronizationLib

+  VmgExitLib

 

 [Pcd]

   gEfiMdeModulePkgTokenSpaceGuid.PcdCpuStackGuard    # CONSUMES

diff --git a/UefiCpuPkg/Library/CpuExceptionHandlerLib/PeiDxeSmmCpuException.c b/UefiCpuPkg/Library/CpuExceptionHandlerLib/PeiDxeSmmCpuException.c
index 6a2670d559..892d349d4b 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 d4ae153c57..01b5a2f1f4 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/SecPeiCpuExceptionHandlerLib.inf b/UefiCpuPkg/Library/CpuExceptionHandlerLib/SecPeiCpuExceptionHandlerLib.inf
index 6d25cafe2c..967cb61ba6 100644
--- a/UefiCpuPkg/Library/CpuExceptionHandlerLib/SecPeiCpuExceptionHandlerLib.inf
+++ b/UefiCpuPkg/Library/CpuExceptionHandlerLib/SecPeiCpuExceptionHandlerLib.inf
@@ -48,3 +48,4 @@
   PrintLib

   LocalApicLib

   PeCoffGetEntryPointLib

+  VmgExitLib

diff --git a/UefiCpuPkg/Library/CpuExceptionHandlerLib/SmmCpuExceptionHandlerLib.inf b/UefiCpuPkg/Library/CpuExceptionHandlerLib/SmmCpuExceptionHandlerLib.inf
index 2ffbbccc30..4cdb11c04e 100644
--- a/UefiCpuPkg/Library/CpuExceptionHandlerLib/SmmCpuExceptionHandlerLib.inf
+++ b/UefiCpuPkg/Library/CpuExceptionHandlerLib/SmmCpuExceptionHandlerLib.inf
@@ -51,4 +51,5 @@
   LocalApicLib

   PeCoffGetEntryPointLib

   DebugLib

+  VmgExitLib

 

diff --git a/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ExceptionHandlerAsm.nasm b/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ExceptionHandlerAsm.nasm
index 3814f9de37..2a5545ecfd 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 19198f2731..26cae56cc5 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

diff --git a/UefiCpuPkg/Library/CpuExceptionHandlerLib/Xcode5SecPeiCpuExceptionHandlerLib.inf b/UefiCpuPkg/Library/CpuExceptionHandlerLib/Xcode5SecPeiCpuExceptionHandlerLib.inf
index 7e21beaab6..743c2aa766 100644
--- a/UefiCpuPkg/Library/CpuExceptionHandlerLib/Xcode5SecPeiCpuExceptionHandlerLib.inf
+++ b/UefiCpuPkg/Library/CpuExceptionHandlerLib/Xcode5SecPeiCpuExceptionHandlerLib.inf
@@ -53,3 +53,4 @@
   PrintLib

   LocalApicLib

   PeCoffGetEntryPointLib

+  VmgExitLib