From f5a6e1bab5d4d9d7bd0d543777290269e6c1a065 Mon Sep 17 00:00:00 2001
From: Brijesh Singh <brijesh.singh@amd.com>
Date: Thu, 9 Dec 2021 11:27:52 +0800
Subject: [PATCH] OvmfPkg/PlatformPei: set the Hypervisor Features PCD

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3275

Version 2 of the GHCB specification added the support to query the
hypervisor feature bitmap. The feature bitmap provide information
such as whether to use the AP create VmgExit or use the AP jump table
approach to create the APs. The MpInitLib will use the
PcdGhcbHypervisorFeatures to determine which method to use for creating
the AP.

Query the hypervisor feature and set the PCD accordingly.

Cc: Michael Roth <michael.roth@amd.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Min Xu <min.m.xu@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Jiewen Yao <Jiewen.yao@intel.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
 OvmfPkg/PlatformPei/AmdSev.c        | 55 +++++++++++++++++++++++++++++
 OvmfPkg/PlatformPei/PlatformPei.inf |  2 ++
 2 files changed, 57 insertions(+)

diff --git a/OvmfPkg/PlatformPei/AmdSev.c b/OvmfPkg/PlatformPei/AmdSev.c
index c60a153a05..9b71f7cf2f 100644
--- a/OvmfPkg/PlatformPei/AmdSev.c
+++ b/OvmfPkg/PlatformPei/AmdSev.c
@@ -24,6 +24,12 @@
 
 #include "Platform.h"
 
+STATIC
+UINT64
+GetHypervisorFeature (
+  VOID
+  );
+
 /**
   Initialize SEV-SNP support if running as an SEV-SNP guest.
 
@@ -36,11 +42,21 @@ AmdSevSnpInitialize (
 {
   EFI_PEI_HOB_POINTERS         Hob;
   EFI_HOB_RESOURCE_DESCRIPTOR  *ResourceHob;
+  UINT64                       HvFeatures;
+  EFI_STATUS                   PcdStatus;
 
   if (!MemEncryptSevSnpIsEnabled ()) {
     return;
   }
 
+  //
+  // Query the hypervisor feature using the VmgExit and set the value in the
+  // hypervisor features PCD.
+  //
+  HvFeatures = GetHypervisorFeature ();
+  PcdStatus  = PcdSet64S (PcdGhcbHypervisorFeatures, HvFeatures);
+  ASSERT_RETURN_ERROR (PcdStatus);
+
   //
   // Iterate through the system RAM and validate it.
   //
@@ -91,6 +107,45 @@ SevEsProtocolFailure (
   CpuDeadLoop ();
 }
 
+/**
+ Get the hypervisor features bitmap
+
+**/
+STATIC
+UINT64
+GetHypervisorFeature (
+  VOID
+  )
+{
+  UINT64                    Status;
+  GHCB                      *Ghcb;
+  MSR_SEV_ES_GHCB_REGISTER  Msr;
+  BOOLEAN                   InterruptState;
+  UINT64                    Features;
+
+  Msr.GhcbPhysicalAddress = AsmReadMsr64 (MSR_SEV_ES_GHCB);
+  Ghcb                    = Msr.Ghcb;
+
+  //
+  // Initialize the GHCB
+  //
+  VmgInit (Ghcb, &InterruptState);
+
+  //
+  // Query the Hypervisor Features.
+  //
+  Status = VmgExit (Ghcb, SVM_EXIT_HYPERVISOR_FEATURES, 0, 0);
+  if ((Status != 0)) {
+    SevEsProtocolFailure (GHCB_TERMINATE_GHCB_GENERAL);
+  }
+
+  Features = Ghcb->SaveArea.SwExitInfo2;
+
+  VmgDone (Ghcb, InterruptState);
+
+  return Features;
+}
+
 /**
 
   This function can be used to register the GHCB GPA.
diff --git a/OvmfPkg/PlatformPei/PlatformPei.inf b/OvmfPkg/PlatformPei/PlatformPei.inf
index bada5ea144..3c05b550e4 100644
--- a/OvmfPkg/PlatformPei/PlatformPei.inf
+++ b/OvmfPkg/PlatformPei/PlatformPei.inf
@@ -62,6 +62,7 @@
   MtrrLib
   MemEncryptSevLib
   PcdLib
+  VmgExitLib
 
 [Pcd]
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfPeiMemFvBase
@@ -107,6 +108,7 @@
   gUefiCpuPkgTokenSpaceGuid.PcdCpuApStackSize
   gUefiCpuPkgTokenSpaceGuid.PcdSevEsIsEnabled
   gEfiMdePkgTokenSpaceGuid.PcdConfidentialComputingGuestAttr
+  gUefiCpuPkgTokenSpaceGuid.PcdGhcbHypervisorFeatures
 
 [FixedPcd]
   gEfiMdePkgTokenSpaceGuid.PcdPciExpressBaseAddress
-- 
2.39.2