From 82bfd2e86d895efd7a9dcb778799bafae7b3ce71 Mon Sep 17 00:00:00 2001
From: Sebastien Boeuf <sebastien.boeuf@intel.com>
Date: Wed, 2 Mar 2022 21:31:36 +0800
Subject: [PATCH] OvmfPkg: CloudHv: Rely on PVH memmap instead of CMOS

Instead of using the CMOS, the CloudHv platform relies on the list of
memmap entries provided through the PVH boot protocol to determine the
last RAM address below 4G.

Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
---
 OvmfPkg/PlatformPei/MemDetect.c     | 73 +++++++++++++++++++++++++++++
 OvmfPkg/PlatformPei/PlatformPei.inf |  2 +
 2 files changed, 75 insertions(+)

diff --git a/OvmfPkg/PlatformPei/MemDetect.c b/OvmfPkg/PlatformPei/MemDetect.c
index 1bcb5a08bc..8ecc8257f9 100644
--- a/OvmfPkg/PlatformPei/MemDetect.c
+++ b/OvmfPkg/PlatformPei/MemDetect.c
@@ -17,6 +17,7 @@ Module Name:
 #include <IndustryStandard/I440FxPiix4.h>
 #include <IndustryStandard/Q35MchIch9.h>
 #include <IndustryStandard/CloudHv.h>
+#include <IndustryStandard/Xen/arch-x86/hvm/start_info.h>
 #include <PiPei.h>
 #include <Register/Intel/SmramSaveStateMap.h>
 
@@ -315,6 +316,73 @@ ScanOrAdd64BitE820Ram (
   return EFI_SUCCESS;
 }
 
+/**
+  Returns PVH memmap
+
+  @param Entries      Pointer to PVH memmap
+  @param Count        Number of entries
+
+  @return EFI_STATUS
+**/
+EFI_STATUS
+GetPvhMemmapEntries (
+  struct hvm_memmap_table_entry  **Entries,
+  UINT32                         *Count
+  )
+{
+  UINT32                 *PVHResetVectorData;
+  struct hvm_start_info  *pvh_start_info;
+
+  PVHResetVectorData = (VOID *)(UINTN)PcdGet32 (PcdXenPvhStartOfDayStructPtr);
+  if (PVHResetVectorData == 0) {
+    return EFI_NOT_FOUND;
+  }
+
+  pvh_start_info = (struct hvm_start_info *)(UINTN)PVHResetVectorData[0];
+
+  *Entries = (struct hvm_memmap_table_entry *)(UINTN)pvh_start_info->memmap_paddr;
+  *Count   = pvh_start_info->memmap_entries;
+
+  return EFI_SUCCESS;
+}
+
+STATIC
+UINT64
+GetHighestSystemMemoryAddressFromPvhMemmap (
+  BOOLEAN  Below4gb
+  )
+{
+  struct hvm_memmap_table_entry  *Memmap;
+  UINT32                         MemmapEntriesCount;
+  struct hvm_memmap_table_entry  *Entry;
+  EFI_STATUS                     Status;
+  UINT32                         Loop;
+  UINT64                         HighestAddress;
+  UINT64                         EntryEnd;
+
+  HighestAddress = 0;
+
+  Status = GetPvhMemmapEntries (&Memmap, &MemmapEntriesCount);
+  ASSERT_EFI_ERROR (Status);
+
+  for (Loop = 0; Loop < MemmapEntriesCount; Loop++) {
+    Entry    = Memmap + Loop;
+    EntryEnd = Entry->addr + Entry->size;
+
+    if ((Entry->type == XEN_HVM_MEMMAP_TYPE_RAM) &&
+        (EntryEnd > HighestAddress))
+    {
+      if (Below4gb && (EntryEnd <= BASE_4GB)) {
+        HighestAddress = EntryEnd;
+      } else if (!Below4gb && (EntryEnd >= BASE_4GB)) {
+        HighestAddress = EntryEnd;
+      }
+    }
+  }
+
+  return HighestAddress;
+}
+
 UINT32
 GetSystemMemorySizeBelow4gb (
   VOID
@@ -325,6 +393,11 @@ GetSystemMemorySizeBelow4gb (
   UINT8       Cmos0x34;
   UINT8       Cmos0x35;
 
+  if (mHostBridgeDevId == CLOUDHV_DEVICE_ID) {
+    // Get the information from PVH memmap
+    return (UINT32)GetHighestSystemMemoryAddressFromPvhMemmap (TRUE);
+  }
+
   Status = ScanOrAdd64BitE820Ram (FALSE, &LowerMemorySize, NULL);
   if ((Status == EFI_SUCCESS) && (LowerMemorySize > 0)) {
     return (UINT32)LowerMemorySize;
diff --git a/OvmfPkg/PlatformPei/PlatformPei.inf b/OvmfPkg/PlatformPei/PlatformPei.inf
index 8ef404168c..212aa7b047 100644
--- a/OvmfPkg/PlatformPei/PlatformPei.inf
+++ b/OvmfPkg/PlatformPei/PlatformPei.inf
@@ -91,6 +91,8 @@
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfDecompressionScratchEnd
   gUefiOvmfPkgTokenSpaceGuid.PcdQ35TsegMbytes
   gUefiOvmfPkgTokenSpaceGuid.PcdQ35SmramAtDefaultSmbase
+  gUefiOvmfPkgTokenSpaceGuid.PcdXenPvhStartOfDayStructPtr
+  gUefiOvmfPkgTokenSpaceGuid.PcdXenPvhStartOfDayStructPtrSize
   gEfiMdePkgTokenSpaceGuid.PcdGuidedExtractHandlerTableAddress
   gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageFtwSpareSize
   gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageVariableSize