[edk2-devel] [RFC PATCH v3 11/43] UefiCpuPkg/CpuExceptionHandler: Add support for CPUID NAE events

[Lendacky, Thomas]

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

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

Add support to construct the required GHCB values to support a CPUID NAE
event. Additionally, CPUID 0x0000_000d requires XCR0 to be supplied in
the GHCB, so add support to issue the XGETBV instruction.

Cc: Eric Dong <eric.dong at intel.com>
Cc: Ray Ni <ray.ni at intel.com>
Cc: Laszlo Ersek <lersek at redhat.com>
Signed-off-by: Tom Lendacky <thomas.lendacky at amd.com>
---
 .../X64/AMDSevVcCommon.c                      | 45 +++++++++++++++++++
 1 file changed, 45 insertions(+)

diff --git a/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/AMDSevVcCommon.c b/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/AMDSevVcCommon.c
index 98b62c21bbce..56f0040fff9f 100644
--- a/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/AMDSevVcCommon.c
+++ b/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/AMDSevVcCommon.c
@@ -11,6 +11,8 @@
 #include <Library/VmgExitLib.h>
 #include "AMDSevVcCommon.h"
 
+#define CR4_OSXSAVE (1 << 18)
+
 typedef enum {
   LongMode64Bit        = 0,
   LongModeCompat32Bit,
@@ -488,6 +490,45 @@ IoioExit (
   return 0;
 }
 
+STATIC
+UINTN
+CpuidExit (
+  GHCB                     *Ghcb,
+  EFI_SYSTEM_CONTEXT_X64   *Regs,
+  SEV_ES_INSTRUCTION_DATA  *InstructionData
+  )
+{
+  UINTN  Status;
+
+  Ghcb->SaveArea.Rax = Regs->Rax;
+  GhcbSetRegValid (Ghcb, GhcbRax);
+  Ghcb->SaveArea.Rcx = Regs->Rcx;
+  GhcbSetRegValid (Ghcb, GhcbRcx);
+  if (Regs->Rax == 0x0000000d) {
+    Ghcb->SaveArea.XCr0 = (AsmReadCr4 () & CR4_OSXSAVE) ? AsmXGetBv (0) : 1;
+    GhcbSetRegValid (Ghcb, GhcbXCr0);
+  }
+
+  Status = VmgExit (Ghcb, SvmExitCpuid, 0, 0);
+  if (Status) {
+    return Status;
+  }
+
+  if (!GhcbIsRegValid (Ghcb, GhcbRax) ||
+      !GhcbIsRegValid (Ghcb, GhcbRbx) ||
+      !GhcbIsRegValid (Ghcb, GhcbRcx) ||
+      !GhcbIsRegValid (Ghcb, GhcbRdx)) {
+    VmgExit (Ghcb, SvmExitUnsupported, SvmExitCpuid, 0);
+    ASSERT (0);
+  }
+  Regs->Rax = Ghcb->SaveArea.Rax;
+  Regs->Rbx = Ghcb->SaveArea.Rbx;
+  Regs->Rcx = Ghcb->SaveArea.Rcx;
+  Regs->Rdx = Ghcb->SaveArea.Rdx;
+
+  return 0;
+}
+
 UINTN
 DoVcCommon (
   GHCB                *Ghcb,
@@ -504,6 +545,10 @@ DoVcCommon (
 
   ExitCode = Regs->ExceptionData;
   switch (ExitCode) {
+  case SvmExitCpuid:
+    NaeExit = CpuidExit;
+    break;
+
   case SvmExitIoioProt:
     NaeExit = IoioExit;
     break;
-- 
2.17.1


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