[edk2-devel] [PATCH v2 3/3] RFC: OvmfPkg/PlatformPei: stop using cmos for memory detection

[Gerd Hoffmann]

Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3593

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

Signed-off-by: Gerd Hoffmann <kra...@redhat.com>
---
 OvmfPkg/PlatformPei/MemDetect.c | 58 ++-------------------------------
 1 file changed, 3 insertions(+), 55 deletions(-)

diff --git a/OvmfPkg/PlatformPei/MemDetect.c b/OvmfPkg/PlatformPei/MemDetect.c
index 20154255324b..8d2c7f432472 100644
--- a/OvmfPkg/PlatformPei/MemDetect.c
+++ b/OvmfPkg/PlatformPei/MemDetect.c
@@ -37,7 +37,6 @@ Module Name:
 #include <Library/QemuFwCfgSimpleParserLib.h>
 
 #include "Platform.h"
-#include "Cmos.h"
 
 UINT8 mPhysMemAddressWidth;
 
@@ -295,52 +294,11 @@ GetSystemMemorySizeBelow4gb (
 {
   EFI_STATUS Status;
   UINT64 LowerMemorySize = 0;
-  UINT8 Cmos0x34;
-  UINT8 Cmos0x35;
 
   Status = ScanOrAdd64BitE820Ram (FALSE, &LowerMemorySize, NULL);
-  if (Status == EFI_SUCCESS && LowerMemorySize > 0) {
-    return LowerMemorySize;
-  }
+  ASSERT (Status == EFI_SUCCESS && LowerMemorySize > 0);
+  return 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);
 }
 
 
@@ -371,12 +329,9 @@ 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;
   }
 
   //
@@ -719,7 +674,6 @@ QemuInitializeRam (
   )
 {
   UINT64                      LowerMemorySize;
-  UINT64                      UpperMemorySize;
   MTRR_SETTINGS               MtrrSettings;
   EFI_STATUS                  Status;
 
@@ -775,12 +729,6 @@ 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);
-      }
-    }
   }
 
   //
-- 
2.31.1



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