[edk2-devel] [PATCH v7 23/31] OvmfPkg/PlatformPei: set the Hypervisor Features PCD

[Brijesh Singh via groups.io]

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 at amd.com>
Cc: James Bottomley <jejb at linux.ibm.com>
Cc: Min Xu <min.m.xu at intel.com>
Cc: Jiewen Yao <jiewen.yao at intel.com>
Cc: Tom Lendacky <thomas.lendacky at amd.com>
Cc: Jordan Justen <jordan.l.justen at intel.com>
Cc: Ard Biesheuvel <ardb+tianocore at kernel.org>
Cc: Erdem Aktas <erdemaktas at google.com>
Cc: Gerd Hoffmann <kraxel at redhat.com>
Acked-by: Jiewen Yao <Jiewen.yao at intel.com>
Signed-off-by: Brijesh Singh <brijesh.singh at amd.com>
---
 OvmfPkg/PlatformPei/PlatformPei.inf |  3 ++
 OvmfPkg/PlatformPei/AmdSev.c        | 56 +++++++++++++++++++++++++++++
 2 files changed, 59 insertions(+)

diff --git a/OvmfPkg/PlatformPei/PlatformPei.inf b/OvmfPkg/PlatformPei/PlatformPei.inf
index 233b9494f64b..d048b692f155 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.PcdConfidentialComputingGuestAttr
+  gUefiCpuPkgTokenSpaceGuid.PcdGhcbHypervisorFeatures
+
 
 [FixedPcd]
   gEfiMdePkgTokenSpaceGuid.PcdPciExpressBaseAddress
diff --git a/OvmfPkg/PlatformPei/AmdSev.c b/OvmfPkg/PlatformPei/AmdSev.c
index 5e2c891309d4..b71a4a7304f7 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 +42,22 @@ 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 +108,45 @@ 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.
-- 
2.17.1



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