From 41d8bb30386ceab55787fc9f5aac6434e2493e27 Mon Sep 17 00:00:00 2001
From: Gerd Hoffmann <kraxel@redhat.com>
Date: Wed, 8 Dec 2021 08:01:46 +0100
Subject: OvmfPkg/PlatformPei: stop using cmos for memory detection

Not needed for qemu 1.7 (released in 2013) and newer.

Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3593
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
---
 OvmfPkg/PlatformPei/MemDetect.c | 59 +++--------------------------------------
 1 file changed, 4 insertions(+), 55 deletions(-)

(limited to 'OvmfPkg/PlatformPei')

diff --git a/OvmfPkg/PlatformPei/MemDetect.c b/OvmfPkg/PlatformPei/MemDetect.c
index 1bcb5a0..fb38e3c 100644
--- a/OvmfPkg/PlatformPei/MemDetect.c
+++ b/OvmfPkg/PlatformPei/MemDetect.c
@@ -38,7 +38,6 @@ Module Name:
 #include <Library/QemuFwCfgSimpleParserLib.h>
 
 #include "Platform.h"
-#include "Cmos.h"
 
 UINT8  mPhysMemAddressWidth;
 
@@ -322,51 +321,11 @@ GetSystemMemorySizeBelow4gb (
 {
   EFI_STATUS  Status;
   UINT64      LowerMemorySize = 0;
-  UINT8       Cmos0x34;
-  UINT8       Cmos0x35;
 
   Status = ScanOrAdd64BitE820Ram (FALSE, &LowerMemorySize, NULL);
-  if ((Status == EFI_SUCCESS) && (LowerMemorySize > 0)) {
-    return (UINT32)LowerMemorySize;
-  }
-
-  //
-  // CMOS 0x34/0x35 specifies the system memory above 16 MB.
-  // * CMOS(0x35) is the high byte
-  // * CMOS(0x34) is the low byte
-  // * The size is specified in 64kb chunks
-  // * Since this is memory above 16MB, the 16MB must be added
-  //   into the calculation to get the total memory size.
-  //
-
-  Cmos0x34 = (UINT8)CmosRead8 (0x34);
-  Cmos0x35 = (UINT8)CmosRead8 (0x35);
-
-  return (UINT32)(((UINTN)((Cmos0x35 << 8) + Cmos0x34) << 16) + SIZE_16MB);
-}
-
-STATIC
-UINT64
-GetSystemMemorySizeAbove4gb (
-  )
-{
-  UINT32  Size;
-  UINTN   CmosIndex;
-
-  //
-  // CMOS 0x5b-0x5d specifies the system memory above 4GB MB.
-  // * CMOS(0x5d) is the most significant size byte
-  // * CMOS(0x5c) is the middle size byte
-  // * CMOS(0x5b) is the least significant size byte
-  // * The size is specified in 64kb chunks
-  //
-
-  Size = 0;
-  for (CmosIndex = 0x5d; CmosIndex >= 0x5b; CmosIndex--) {
-    Size = (UINT32)(Size << 8) + (UINT32)CmosRead8 (CmosIndex);
-  }
-
-  return LShiftU64 (Size, 16);
+  ASSERT_EFI_ERROR (Status);
+  ASSERT (LowerMemorySize > 0);
+  return (UINT32)LowerMemorySize;
 }
 
 /**
@@ -396,12 +355,9 @@ GetFirstNonAddress (
   // If QEMU presents an E820 map, then get the highest exclusive >=4GB RAM
   // address from it. This can express an address >= 4GB+1TB.
   //
-  // 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 (FALSE, NULL, &FirstNonAddress);
   if (EFI_ERROR (Status)) {
-    FirstNonAddress = BASE_4GB + GetSystemMemorySizeAbove4gb ();
+    FirstNonAddress = BASE_4GB;
   }
 
   //
@@ -773,7 +729,6 @@ QemuInitializeRam (
   )
 {
   UINT64         LowerMemorySize;
-  UINT64         UpperMemorySize;
   MTRR_SETTINGS  MtrrSettings;
   EFI_STATUS     Status;
 
@@ -832,12 +787,6 @@ QemuInitializeRam (
     // memory size read from the CMOS.
     //
     Status = ScanOrAdd64BitE820Ram (TRUE, NULL, NULL);
-    if (EFI_ERROR (Status)) {
-      UpperMemorySize = GetSystemMemorySizeAbove4gb ();
-      if (UpperMemorySize != 0) {
-        AddMemoryBaseSizeHob (BASE_4GB, UpperMemorySize);
-      }
-    }
   }
 
   //
-- 
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