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>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
 OvmfPkg/PlatformPei/PlatformPei.inf |  3 ++
 OvmfPkg/PlatformPei/AmdSev.c        | 55 +++++++++++++++++++++++++++++
 2 files changed, 58 insertions(+)

diff --git a/OvmfPkg/PlatformPei/PlatformPei.inf b/OvmfPkg/PlatformPei/PlatformPei.inf
index c8c89ab648d0..8c9795095a10 100644
--- a/OvmfPkg/PlatformPei/PlatformPei.inf
+++ b/OvmfPkg/PlatformPei/PlatformPei.inf
@@ -62,6 +62,7 @@ [LibraryClasses]
   MtrrLib
   MemEncryptSevLib
   PcdLib
+  VmgExitLib
 
 [Pcd]
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfPeiMemFvBase
@@ -107,6 +108,8 @@ [Pcd]
   gUefiCpuPkgTokenSpaceGuid.PcdCpuApStackSize
   gUefiCpuPkgTokenSpaceGuid.PcdSevEsIsEnabled
   gUefiCpuPkgTokenSpaceGuid.PcdSevSnpIsEnabled
+  gUefiCpuPkgTokenSpaceGuid.PcdGhcbHypervisorFeatures
+
 
 [FixedPcd]
   gEfiMdePkgTokenSpaceGuid.PcdPciExpressBaseAddress
diff --git a/OvmfPkg/PlatformPei/AmdSev.c b/OvmfPkg/PlatformPei/AmdSev.c
index ec577ef3efcc..b488cd5aed9b 100644
--- a/OvmfPkg/PlatformPei/AmdSev.c
+++ b/OvmfPkg/PlatformPei/AmdSev.c
@@ -23,6 +23,12 @@
 
 #include "Platform.h"
 
+STATIC
+UINT64
+GetHypervisorFeature (
+  VOID
+  );
+
 /**
   Initialize SEV-SNP support if running as an SEV-SNP guest.
 
@@ -36,6 +42,7 @@ AmdSevSnpInitialize (
   RETURN_STATUS                 PcdStatus;
   EFI_PEI_HOB_POINTERS          Hob;
   EFI_HOB_RESOURCE_DESCRIPTOR   *ResourceHob;
+  UINT64                        HvFeatures;
 
   if (!MemEncryptSevSnpIsEnabled ()) {
     return;
@@ -44,6 +51,15 @@ AmdSevSnpInitialize (
   PcdStatus = PcdSetBoolS (PcdSevSnpIsEnabled, TRUE);
   ASSERT_RETURN_ERROR (PcdStatus);
 
+  //
+  // 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.
   //
@@ -94,6 +110,45 @@ SevEsProtocolFailure (
   CpuDeadLoop ();
 }
 
+/**
+ Get the hypervisor features bitmap
+
+**/
+STATIC
+UINT64
+GetHypervisorFeature (
+  VOID
+  )
+{
+  RETURN_STATUS                   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.
-- 
2.17.1



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