[PATCH 3/3] OvmfPkg: CloudHv: Rely on PVH memmap instead of CMOS

["Boeuf, Sebastien" <sebastien.boeuf@intel.com>]

From: Sebastien Boeuf <sebastien.boeuf@intel.com>

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.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@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
-- 
2.32.0

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