[PATCH v4 15/40] UefiCpuPkg/CpuExceptionHandler: Add support for RDTSC NAE events

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

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

Under SEV-ES, a RDTSC intercept generates a #VC exception. VMGEXIT must be
used to allow the hypervisor to handle this intercept.

Cc: Eric Dong <eric.dong@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
 .../X64/AMDSevVcCommon.c                      | 29 +++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/AMDSevVcCommon.c b/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/AMDSevVcCommon.c
index 03003e9113fa..552fe2e1a343 100644
--- a/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/AMDSevVcCommon.c
+++ b/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/AMDSevVcCommon.c
@@ -894,6 +894,31 @@ CpuidExit (
   return 0;
 }
 
+STATIC
+UINT64
+RdtscExit (
+  GHCB                     *Ghcb,
+  EFI_SYSTEM_CONTEXT_X64   *Regs,
+  SEV_ES_INSTRUCTION_DATA  *InstructionData
+  )
+{
+  UINT64  Status;
+
+  Status = VmgExit (Ghcb, SvmExitRdtsc, 0, 0);
+  if (Status) {
+    return Status;
+  }
+
+  if (!GhcbIsRegValid (Ghcb, GhcbRax) ||
+      !GhcbIsRegValid (Ghcb, GhcbRdx)) {
+    return UnsupportedExit (Ghcb, Regs, InstructionData);
+  }
+  Regs->Rax = Ghcb->SaveArea.Rax;
+  Regs->Rdx = Ghcb->SaveArea.Rdx;
+
+  return 0;
+}
+
 UINTN
 DoVcCommon (
   GHCB                *Ghcb,
@@ -910,6 +935,10 @@ DoVcCommon (
 
   ExitCode = Regs->ExceptionData;
   switch (ExitCode) {
+  case SvmExitRdtsc:
+    NaeExit = RdtscExit;
+    break;
+
   case SvmExitCpuid:
     NaeExit = CpuidExit;
     break;
-- 
2.17.1