[PATCH v4 1/6] OvmfPkg: Realize EfiMemoryAcceptProtocol in AmdSevDxe

["Dionna Glaze" <dionnaglaze@google.com>]

From: Sophia Wolf <phiawolf@google.com>

When a guest OS does not support unaccepted memory, the unaccepted
memory must be accepted before returning a memory map to the caller.

EfiMemoryAcceptProtocol is defined in MdePkg and is implemented /
Installed in AmdSevDxe for AMD SEV-SNP memory acceptance.

Cc: Gerd Hoffmann <kraxel@redhat.com>
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>

Signed-off-by: Sophia Wolf <phiawolf@google.com>
---
 OvmfPkg/AmdSevDxe/AmdSevDxe.c                                      | 34 ++++++++++++++++++++
 OvmfPkg/AmdSevDxe/AmdSevDxe.inf                                    |  3 ++
 OvmfPkg/Library/BaseMemEncryptSevLib/X64/DxeSnpSystemRamValidate.c | 24 +++++++++++---
 3 files changed, 57 insertions(+), 4 deletions(-)

diff --git a/OvmfPkg/AmdSevDxe/AmdSevDxe.c b/OvmfPkg/AmdSevDxe/AmdSevDxe.c
index 662d3c4ccb..09aa15165d 100644
--- a/OvmfPkg/AmdSevDxe/AmdSevDxe.c
+++ b/OvmfPkg/AmdSevDxe/AmdSevDxe.c
@@ -20,6 +20,7 @@
 #include <Library/UefiBootServicesTableLib.h>
 #include <Guid/ConfidentialComputingSevSnpBlob.h>
 #include <Library/PcdLib.h>
+#include <Protocol/MemoryAccept.h>
 
 STATIC CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION  mSnpBootDxeTable = {
   SIGNATURE_32 ('A',                                    'M', 'D', 'E'),
@@ -31,6 +32,29 @@ STATIC CONFIDENTIAL_COMPUTING_SNP_BLOB_LOCATION  mSnpBootDxeTable = {
   FixedPcdGet32 (PcdOvmfCpuidSize),
 };
 
+STATIC EFI_HANDLE mAmdSevDxeHandle = NULL;
+
+STATIC
+EFI_STATUS
+EFIAPI
+AmdSevMemoryAccept (
+  IN EFI_MEMORY_ACCEPT_PROTOCOL *This,
+  IN EFI_PHYSICAL_ADDRESS StartAddress,
+  IN UINTN Size
+)
+{
+  MemEncryptSevSnpPreValidateSystemRam (
+    StartAddress,
+    EFI_SIZE_TO_PAGES (Size)
+    );
+
+  return EFI_SUCCESS;
+}
+
+STATIC EFI_MEMORY_ACCEPT_PROTOCOL mMemoryAcceptProtocol = {
+  AmdSevMemoryAccept
+};
+
 EFI_STATUS
 EFIAPI
 AmdSevDxeEntryPoint (
@@ -147,6 +171,16 @@ AmdSevDxeEntryPoint (
     }
   }
 
+  Status = gBS->InstallProtocolInterface (
+                  &mAmdSevDxeHandle,
+                  &gEfiMemoryAcceptProtocolGuid,
+                  EFI_NATIVE_INTERFACE,
+                  &mMemoryAcceptProtocol
+                  );
+  if (EFI_ERROR (Status)) {
+    DEBUG ((DEBUG_ERROR, "Install EfiMemoryAcceptProtocol failed.\n"));
+  }
+
   //
   // If its SEV-SNP active guest then install the CONFIDENTIAL_COMPUTING_SEV_SNP_BLOB.
   // It contains the location for both the Secrets and CPUID page.
diff --git a/OvmfPkg/AmdSevDxe/AmdSevDxe.inf b/OvmfPkg/AmdSevDxe/AmdSevDxe.inf
index 9acf860cf2..5ddddabc32 100644
--- a/OvmfPkg/AmdSevDxe/AmdSevDxe.inf
+++ b/OvmfPkg/AmdSevDxe/AmdSevDxe.inf
@@ -47,6 +47,9 @@
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpSecretsBase
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfSnpSecretsSize
 
+[Protocols]
+  gEfiMemoryAcceptProtocolGuid
+
 [Guids]
   gConfidentialComputingSevSnpBlobGuid
 
diff --git a/OvmfPkg/Library/BaseMemEncryptSevLib/X64/DxeSnpSystemRamValidate.c b/OvmfPkg/Library/BaseMemEncryptSevLib/X64/DxeSnpSystemRamValidate.c
index d3a95e4913..ee3710f7b3 100644
--- a/OvmfPkg/Library/BaseMemEncryptSevLib/X64/DxeSnpSystemRamValidate.c
+++ b/OvmfPkg/Library/BaseMemEncryptSevLib/X64/DxeSnpSystemRamValidate.c
@@ -14,6 +14,7 @@
 #include <Library/MemEncryptSevLib.h>
 
 #include "SnpPageStateChange.h"
+#include "VirtualMemory.h"
 
 /**
   Pre-validate the system RAM when SEV-SNP is enabled in the guest VM.
@@ -29,12 +30,27 @@ MemEncryptSevSnpPreValidateSystemRam (
   IN UINTN             NumPages
   )
 {
+  EFI_STATUS Status;
+
   if (!MemEncryptSevSnpIsEnabled ()) {
     return;
   }
 
-  //
-  // All the pre-validation must be completed in the PEI phase.
-  //
-  ASSERT (FALSE);
+  // DXE pre-validation may happen with the memory accept protocol.
+  // The protocol should only be called outside the prevalidated ranges
+  // that the PEI stage code explicitly skips. Specifically, only memory
+  // ranges that are classified as unaccepted.
+  if (BaseAddress >= SIZE_4GB) {
+    Status = InternalMemEncryptSevCreateIdentityMap1G (
+               0,
+               BaseAddress,
+               EFI_PAGES_TO_SIZE (NumPages)
+               );
+    if (EFI_ERROR (Status)) {
+      ASSERT (FALSE);
+      CpuDeadLoop ();
+    }
+  }
+
+  InternalSetPageState (BaseAddress, NumPages, SevSnpPagePrivate, TRUE);
 }
-- 
2.37.3.998.g577e59143f-goog