From 557dede8a6b88ee14f541b7f96ff60830b98329a Mon Sep 17 00:00:00 2001
From: Gerd Hoffmann <kraxel@redhat.com>
Date: Wed, 8 Dec 2021 08:01:44 +0100
Subject: [PATCH] OvmfPkg/PlatformPei: ScanOrAdd64BitE820Ram improvements

Add a bool parameter to ScanOrAdd64BitE820Ram to explicitly specify
whenever ScanOrAdd64BitE820Ram should add HOBs for high memory (above
4G) or scan only.

Also add a lowmem parameter so ScanOrAdd64BitE820Ram
can report the memory size below 4G.

This allows a more flexible usage of ScanOrAdd64BitE820Ram,
a followup patch will use it for all memory detection.

No functional change.

Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3593
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Philippe Mathieu-Daude <philmd@redhat.com>
---
 OvmfPkg/PlatformPei/MemDetect.c | 32 ++++++++++++++++++++++++--------
 1 file changed, 24 insertions(+), 8 deletions(-)

diff --git a/OvmfPkg/PlatformPei/MemDetect.c b/OvmfPkg/PlatformPei/MemDetect.c
index 934d5c1965..b0b7e466a7 100644
--- a/OvmfPkg/PlatformPei/MemDetect.c
+++ b/OvmfPkg/PlatformPei/MemDetect.c
@@ -223,6 +223,8 @@ QemuUc32BaseInitialization (
 STATIC
 EFI_STATUS
 ScanOrAdd64BitE820Ram (
+  IN BOOLEAN  AddHighHob,
+  OUT UINT64  *LowMemory OPTIONAL,
   OUT UINT64  *MaxAddress OPTIONAL
   )
 {
@@ -241,6 +243,10 @@ ScanOrAdd64BitE820Ram (
     return EFI_PROTOCOL_ERROR;
   }
 
+  if (LowMemory != NULL) {
+    *LowMemory = 0;
+  }
+
   if (MaxAddress != NULL) {
     *MaxAddress = BASE_4GB;
   }
@@ -256,10 +262,8 @@ ScanOrAdd64BitE820Ram (
       E820Entry.Length,
       E820Entry.Type
       ));
-    if ((E820Entry.Type == EfiAcpiAddressRangeMemory) &&
-        (E820Entry.BaseAddr >= BASE_4GB))
-    {
-      if (MaxAddress == NULL) {
+    if (E820Entry.Type == EfiAcpiAddressRangeMemory) {
+      if (AddHighHob && (E820Entry.BaseAddr >= BASE_4GB)) {
         UINT64  Base;
         UINT64  End;
 
@@ -279,11 +283,13 @@ ScanOrAdd64BitE820Ram (
             End
             ));
         }
-      } else {
+      }
+
+      if (MaxAddress || LowMemory) {
         UINT64  Candidate;
 
         Candidate = E820Entry.BaseAddr + E820Entry.Length;
-        if (Candidate > *MaxAddress) {
+        if (MaxAddress && (Candidate > *MaxAddress)) {
           *MaxAddress = Candidate;
           DEBUG ((
             DEBUG_VERBOSE,
@@ -292,6 +298,16 @@ ScanOrAdd64BitE820Ram (
             *MaxAddress
             ));
         }
+
+        if (LowMemory && (Candidate > *LowMemory) && (Candidate < BASE_4GB)) {
+          *LowMemory = Candidate;
+          DEBUG ((
+            DEBUG_VERBOSE,
+            "%a: LowMemory=0x%Lx\n",
+            __FUNCTION__,
+            *LowMemory
+            ));
+        }
       }
     }
   }
@@ -376,7 +392,7 @@ GetFirstNonAddress (
   // Otherwise, get the flat size of the memory above 4GB from the CMOS (which
   // can only express a size smaller than 1TB), and add it to 4GB.
   //
-  Status = ScanOrAdd64BitE820Ram (&FirstNonAddress);
+  Status = ScanOrAdd64BitE820Ram (FALSE, NULL, &FirstNonAddress);
   if (EFI_ERROR (Status)) {
     FirstNonAddress = BASE_4GB + GetSystemMemorySizeAbove4gb ();
   }
@@ -809,7 +825,7 @@ QemuInitializeRam (
     // entries. Otherwise, create a single memory HOB with the flat >=4GB
     // memory size read from the CMOS.
     //
-    Status = ScanOrAdd64BitE820Ram (NULL);
+    Status = ScanOrAdd64BitE820Ram (TRUE, NULL, NULL);
     if (EFI_ERROR (Status) && (UpperMemorySize != 0)) {
       AddMemoryBaseSizeHob (BASE_4GB, UpperMemorySize);
     }