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>

Author: Sebastien Boeuf

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;

OvmfPkg/PlatformPei/PlatformPei.inf

@@ -91,6 +91,8 @@
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfDecompressionScratchEnd
   gUefiOvmfPkgTokenSpaceGuid.PcdQ35TsegMbytes
   gUefiOvmfPkgTokenSpaceGuid.PcdQ35SmramAtDefaultSmbase
+  gUefiOvmfPkgTokenSpaceGuid.PcdXenPvhStartOfDayStructPtr
+  gUefiOvmfPkgTokenSpaceGuid.PcdXenPvhStartOfDayStructPtrSize
   gEfiMdePkgTokenSpaceGuid.PcdGuidedExtractHandlerTableAddress
   gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageFtwSpareSize
   gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageVariableSize