[PATCH v2 22/31] OvmfPkg/XenPlatformPei: Rework memory detection

["Anthony PERARD" <anthony.perard@citrix.com>]

When running as a Xen PVH guest, there is no CMOS to read the memory
size from.  Rework GetSystemMemorySize(Below|Above)4gb() so they can
works without CMOS by reading the e820 table.

Rework XenPublishRamRegions for PVH, handle the Reserve type and explain
about the ACPI type. MTRR settings aren't modified anymore, on HVM, it's
already done by hvmloader, on PVH it is supposed to have sane default.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
---

Notes:
    About MTRR, should we redo the setting in OVMF? Even if in both case of
    PVH and HVM, something would have setup the default type to write back
    and handle a few other ranges like PCI hole, hvmloader for HVM or and
    libxc I think for PVH.
    
    (For PVH, it's in the spec as well
    https://xenbits.xenproject.org/docs/unstable/misc/pvh.html#mtrr )

 OvmfPkg/XenPlatformPei/Platform.h  |  6 ++
 OvmfPkg/XenPlatformPei/MemDetect.c | 71 ++++++++++++++++++++
 OvmfPkg/XenPlatformPei/Xen.c       | 47 +++++++++----
 3 files changed, 111 insertions(+), 13 deletions(-)

diff --git a/OvmfPkg/XenPlatformPei/Platform.h b/OvmfPkg/XenPlatformPei/Platform.h
index c5a139f016..d6d93eab2d 100644
--- a/OvmfPkg/XenPlatformPei/Platform.h
+++ b/OvmfPkg/XenPlatformPei/Platform.h
@@ -120,6 +120,12 @@ XenPublishRamRegions (
   VOID
   );
 
+EFI_STATUS
+XenGetE820Map (
+  EFI_E820_ENTRY64 **Entries,
+  UINT32 *Count
+  );
+
 extern EFI_BOOT_MODE mBootMode;
 
 extern UINT8 mPhysMemAddressWidth;
diff --git a/OvmfPkg/XenPlatformPei/MemDetect.c b/OvmfPkg/XenPlatformPei/MemDetect.c
index db3d387d1c..0c066d518b 100644
--- a/OvmfPkg/XenPlatformPei/MemDetect.c
+++ b/OvmfPkg/XenPlatformPei/MemDetect.c
@@ -102,6 +102,47 @@ Q35TsegMbytesInitialization (
   mQ35TsegMbytes = ExtendedTsegMbytes;
 }
 
+STATIC
+UINT64
+GetHighestSystemMemoryAddress (
+  BOOLEAN       Below4gb
+  )
+{
+  EFI_E820_ENTRY64    *E820Map;
+  UINT32              E820EntriesCount;
+  EFI_E820_ENTRY64    *Entry;
+  EFI_STATUS          Status;
+  UINT32              Loop;
+  UINT64              HighestAddress;
+  UINT64              EntryEnd;
+
+  HighestAddress = 0;
+
+  Status = XenGetE820Map (&E820Map, &E820EntriesCount);
+  ASSERT_EFI_ERROR (Status);
+
+  for (Loop = 0; Loop < E820EntriesCount; Loop++) {
+    Entry = E820Map + Loop;
+    EntryEnd = Entry->BaseAddr + Entry->Length;
+
+    if (Entry->Type == EfiAcpiAddressRangeMemory &&
+        EntryEnd > HighestAddress) {
+
+      if (Below4gb && (EntryEnd <= BASE_4GB)) {
+        HighestAddress = EntryEnd;
+      } else if (!Below4gb && (EntryEnd >= BASE_4GB)) {
+        HighestAddress = EntryEnd;
+      }
+    }
+  }
+
+  //
+  // Round down the end address.
+  //
+  HighestAddress &= ~(UINT64)EFI_PAGE_MASK;
+
+  return HighestAddress;
+}
 
 UINT32
 GetSystemMemorySizeBelow4gb (
@@ -111,6 +152,19 @@ GetSystemMemorySizeBelow4gb (
   UINT8 Cmos0x34;
   UINT8 Cmos0x35;
 
+  //
+  // In PVH case, there is no CMOS, we have to calculate the memory size
+  // from parsing the E820
+  //
+  if (XenPvhDetected ()) {
+    UINT64  HighestAddress;
+
+    HighestAddress = GetHighestSystemMemoryAddress (TRUE);
+    ASSERT (HighestAddress > 0 && HighestAddress <= BASE_4GB);
+
+    return HighestAddress;
+  }
+
   //
   // CMOS 0x34/0x35 specifies the system memory above 16 MB.
   // * CMOS(0x35) is the high byte
@@ -135,6 +189,23 @@ GetSystemMemorySizeAbove4gb (
   UINT32 Size;
   UINTN  CmosIndex;
 
+  //
+  // In PVH case, there is no CMOS, we have to calculate the memory size
+  // from parsing the E820
+  //
+  if (XenPvhDetected ()) {
+    UINT64  HighestAddress;
+
+    HighestAddress = GetHighestSystemMemoryAddress (FALSE);
+    ASSERT (HighestAddress == 0 || HighestAddress >= BASE_4GB);
+
+    if (HighestAddress >= BASE_4GB) {
+      HighestAddress -= BASE_4GB;
+    }
+
+    return HighestAddress;
+  }
+
   //
   // CMOS 0x5b-0x5d specifies the system memory above 4GB MB.
   // * CMOS(0x5d) is the most significant size byte
diff --git a/OvmfPkg/XenPlatformPei/Xen.c b/OvmfPkg/XenPlatformPei/Xen.c
index f8cee671d8..7b503f2c4e 100644
--- a/OvmfPkg/XenPlatformPei/Xen.c
+++ b/OvmfPkg/XenPlatformPei/Xen.c
@@ -282,6 +282,8 @@ XenPublishRamRegions (
   EFI_E820_ENTRY64  *E820Map;
   UINT32            E820EntriesCount;
   EFI_STATUS        Status;
+  EFI_E820_ENTRY64 *Entry;
+  UINTN Index;
 
   DEBUG ((EFI_D_INFO, "Using memory map provided by Xen\n"));
 
@@ -290,26 +292,45 @@ XenPublishRamRegions (
   //
   E820EntriesCount = 0;
   Status = XenGetE820Map (&E820Map, &E820EntriesCount);
-
   ASSERT_EFI_ERROR (Status);
 
-  if (E820EntriesCount > 0) {
-    EFI_E820_ENTRY64 *Entry;
-    UINT32 Loop;
+  for (Index = 0; Index < E820EntriesCount; Index++) {
+    UINT64 Base;
+    UINT64 End;
 
-    for (Loop = 0; Loop < E820EntriesCount; Loop++) {
-      Entry = E820Map + Loop;
+    Entry = &E820Map[Index];
 
+
+    //
+    // Round up the start address, and round down the end address.
+    //
+    Base = ALIGN_VALUE (Entry->BaseAddr, (UINT64)EFI_PAGE_SIZE);
+    End = (Entry->BaseAddr + Entry->Length) & ~(UINT64)EFI_PAGE_MASK;
+
+    switch (Entry->Type) {
+    case EfiAcpiAddressRangeMemory:
+      AddMemoryRangeHob (Base, End);
+      break;
+    case EfiAcpiAddressRangeACPI:
+      //
+      // Ignore, OVMF should read the ACPI tables and provide them to linux
+      // from a different location.
+      //
+      break;
+    case EfiAcpiAddressRangeReserved:
       //
-      // Only care about RAM
+      // Avoid ranges marked as reserved in the e820 table provided by
+      // hvmloader as it conflicts with an other aperture.
+      // error message: CpuDxe: IntersectMemoryDescriptor:
+      //        desc [FC000000, 100000000) type 1 cap 8700000000026001
+      //        conflicts with aperture [FEE00000, FEE01000) cap 1
       //
-      if (Entry->Type != EfiAcpiAddressRangeMemory) {
-        continue;
+      if (!XenHvmloaderDetected ()) {
+        AddReservedMemoryBaseSizeHob (Base, End - Base, FALSE);
       }
-
-      AddMemoryBaseSizeHob (Entry->BaseAddr, Entry->Length);
-
-      MtrrSetMemoryAttribute (Entry->BaseAddr, Entry->Length, CacheWriteBack);
+      break;
+    default:
+      break;
     }
   }
 }
-- 
Anthony PERARD