[PATCH v2 2/8] OvmfPkg/PlatformPei: prepare for PcdQ35TsegMbytes becoming dynamic

[Laszlo Ersek <lersek@redhat.com>]

In one of the next patches we'll turn PcdQ35TsegMbytes into a dynamic PCD,
to be set by PlatformPei. Introduce the Q35TsegMbytesInitialization()
function and the "mQ35TsegMbytes" global variable to support this.

Q35TsegMbytesInitialization() manages the PCD and caches its final value
into "mQ35TsegMbytes". Call Q35TsegMbytesInitialization() from
InitializePlatform() just in time for the current PCD consumers,
PublishPeiMemory(), InitializeRamRegions() and QemuInitializeRam() --
which is called from InitializeRamRegions() -- to be rebased on top of
"mQ35TsegMbytes".

Call Q35TsegMbytesInitialization() only when PcdSmmSmramRequire is TRUE,
given that PcdQ35TsegMbytes is consumed in that case only.

Cc: Jordan Justen <jordan.l.justen@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
---
 OvmfPkg/PlatformPei/Platform.h  |  5 +++++
 OvmfPkg/PlatformPei/MemDetect.c | 17 ++++++++++++++---
 OvmfPkg/PlatformPei/Platform.c  |  4 ++++
 3 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/OvmfPkg/PlatformPei/Platform.h b/OvmfPkg/PlatformPei/Platform.h
index 18f42c3f0ea8..d2d627b221c4 100644
--- a/OvmfPkg/PlatformPei/Platform.h
+++ b/OvmfPkg/PlatformPei/Platform.h
@@ -49,14 +49,19 @@ AddReservedMemoryBaseSizeHob (
   );
 
 VOID
 AddressWidthInitialization (
   VOID
   );
 
+VOID
+Q35TsegMbytesInitialization (
+  VOID
+  );
+
 EFI_STATUS
 PublishPeiMemory (
   VOID
   );
 
 UINT32
 GetSystemMemorySizeBelow4gb (
diff --git a/OvmfPkg/PlatformPei/MemDetect.c b/OvmfPkg/PlatformPei/MemDetect.c
index 78a8e0de346c..886d23622665 100644
--- a/OvmfPkg/PlatformPei/MemDetect.c
+++ b/OvmfPkg/PlatformPei/MemDetect.c
@@ -38,14 +38,25 @@ Module Name:
 #include "Cmos.h"
 
 UINT8 mPhysMemAddressWidth;
 
 STATIC UINT32 mS3AcpiReservedMemoryBase;
 STATIC UINT32 mS3AcpiReservedMemorySize;
 
+STATIC UINT16 mQ35TsegMbytes;
+
+VOID
+Q35TsegMbytesInitialization (
+  VOID
+  )
+{
+  mQ35TsegMbytes = PcdGet16 (PcdQ35TsegMbytes);
+}
+
+
 UINT32
 GetSystemMemorySizeBelow4gb (
   VOID
   )
 {
   UINT8 Cmos0x34;
   UINT8 Cmos0x35;
@@ -344,15 +355,15 @@ PublishPeiMemory (
   UINT32                      PeiMemoryCap;
 
   LowerMemorySize = GetSystemMemorySizeBelow4gb ();
   if (FeaturePcdGet (PcdSmmSmramRequire)) {
     //
     // TSEG is chipped from the end of low RAM
     //
-    LowerMemorySize -= FixedPcdGet16 (PcdQ35TsegMbytes) * SIZE_1MB;
+    LowerMemorySize -= mQ35TsegMbytes * SIZE_1MB;
   }
 
   //
   // If S3 is supported, then the S3 permanent PEI memory is placed next,
   // downwards. Its size is primarily dictated by CpuMpPei. The formula below
   // is an approximation.
   //
@@ -452,15 +463,15 @@ QemuInitializeRam (
     // Create memory HOBs
     //
     AddMemoryRangeHob (0, BASE_512KB + BASE_128KB);
 
     if (FeaturePcdGet (PcdSmmSmramRequire)) {
       UINT32 TsegSize;
 
-      TsegSize = FixedPcdGet16 (PcdQ35TsegMbytes) * SIZE_1MB;
+      TsegSize = mQ35TsegMbytes * SIZE_1MB;
       AddMemoryRangeHob (BASE_1MB, LowerMemorySize - TsegSize);
       AddReservedMemoryBaseSizeHob (LowerMemorySize - TsegSize, TsegSize,
         TRUE);
     } else {
       AddMemoryRangeHob (BASE_1MB, LowerMemorySize);
     }
 
@@ -601,15 +612,15 @@ InitializeRamRegions (
     if (FeaturePcdGet (PcdSmmSmramRequire)) {
       UINT32 TsegSize;
 
       //
       // Make sure the TSEG area that we reported as a reserved memory resource
       // cannot be used for reserved memory allocations.
       //
-      TsegSize = FixedPcdGet16 (PcdQ35TsegMbytes) * SIZE_1MB;
+      TsegSize = mQ35TsegMbytes * SIZE_1MB;
       BuildMemoryAllocationHob (
         GetSystemMemorySizeBelow4gb() - TsegSize,
         TsegSize,
         EfiReservedMemoryType
         );
     }
   }
diff --git a/OvmfPkg/PlatformPei/Platform.c b/OvmfPkg/PlatformPei/Platform.c
index 3e9fda7c7ab0..b8a28450d6c5 100644
--- a/OvmfPkg/PlatformPei/Platform.c
+++ b/OvmfPkg/PlatformPei/Platform.c
@@ -641,14 +641,18 @@ InitializePlatform (
   }
 
   S3Verification ();
   BootModeInitialization ();
   AddressWidthInitialization ();
   MaxCpuCountInitialization ();
 
+  if (FeaturePcdGet (PcdSmmSmramRequire)) {
+    Q35TsegMbytesInitialization ();
+  }
+
   PublishPeiMemory ();
 
   InitializeRamRegions ();
 
   if (mXen) {
     DEBUG ((EFI_D_INFO, "Xen was detected\n"));
     InitializeXen ();
-- 
2.13.1.3.g8be5a757fa67