Introduce the Q35SmramAtDefaultSmbaseInitialization() function for
detecting the "SMRAM at default SMBASE" feature.

For now, the function is only a skeleton, so that we can gradually build
upon the result while the result is hard-coded as FALSE. The actual
detection will occur in a later patch.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=1512
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>
---

Notes:
    v2:
    - trim Cc list
    - pick up Jiewen's R-b <https://edk2.groups.io/g/devel/message/48166>

 OvmfPkg/PlatformPei/PlatformPei.inf |  1 +
 OvmfPkg/PlatformPei/Platform.h      |  7 +++++++
 OvmfPkg/PlatformPei/MemDetect.c     | 18 ++++++++++++++++++
 OvmfPkg/PlatformPei/Platform.c      |  1 +
 4 files changed, 27 insertions(+)

diff --git a/OvmfPkg/PlatformPei/PlatformPei.inf b/OvmfPkg/PlatformPei/PlatformPei.inf
index 30eaebdfae63..25229618ed13 100644
--- a/OvmfPkg/PlatformPei/PlatformPei.inf
+++ b/OvmfPkg/PlatformPei/PlatformPei.inf
@@ -84,6 +84,7 @@ [Pcd]
   gUefiOvmfPkgTokenSpaceGuid.PcdPciMmio64Size
   gUefiOvmfPkgTokenSpaceGuid.PcdOvmfDecompressionScratchEnd
   gUefiOvmfPkgTokenSpaceGuid.PcdQ35TsegMbytes
+  gUefiOvmfPkgTokenSpaceGuid.PcdQ35SmramAtDefaultSmbase
   gEfiMdePkgTokenSpaceGuid.PcdGuidedExtractHandlerTableAddress
   gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageFtwSpareSize
   gEfiMdeModulePkgTokenSpaceGuid.PcdFlashNvStorageVariableSize
diff --git a/OvmfPkg/PlatformPei/Platform.h b/OvmfPkg/PlatformPei/Platform.h
index 2f3cebcd3a6a..43f20f067f22 100644
--- a/OvmfPkg/PlatformPei/Platform.h
+++ b/OvmfPkg/PlatformPei/Platform.h
@@ -52,6 +52,11 @@ Q35TsegMbytesInitialization (
   VOID
   );
 
+VOID
+Q35SmramAtDefaultSmbaseInitialization (
+  VOID
+  );
+
 EFI_STATUS
 PublishPeiMemory (
   VOID
@@ -119,6 +124,8 @@ extern UINT32 mMaxCpuCount;
 
 extern UINT16 mHostBridgeDevId;
 
+extern BOOLEAN mQ35SmramAtDefaultSmbase;
+
 extern UINT32 mQemuUc32Base;
 
 #endif // _PLATFORM_PEI_H_INCLUDED_
diff --git a/OvmfPkg/PlatformPei/MemDetect.c b/OvmfPkg/PlatformPei/MemDetect.c
index 58b171fba1c8..2bc1c46dffc2 100644
--- a/OvmfPkg/PlatformPei/MemDetect.c
+++ b/OvmfPkg/PlatformPei/MemDetect.c
@@ -43,6 +43,8 @@ STATIC UINT32 mS3AcpiReservedMemorySize;
 
 STATIC UINT16 mQ35TsegMbytes;
 
+BOOLEAN mQ35SmramAtDefaultSmbase;
+
 UINT32 mQemuUc32Base;
 
 VOID
@@ -90,6 +92,22 @@ Q35TsegMbytesInitialization (
 }
 
 
+VOID
+Q35SmramAtDefaultSmbaseInitialization (
+  VOID
+  )
+{
+  RETURN_STATUS PcdStatus;
+
+  ASSERT (mHostBridgeDevId == INTEL_Q35_MCH_DEVICE_ID);
+
+  mQ35SmramAtDefaultSmbase = FALSE;
+  PcdStatus = PcdSetBoolS (PcdQ35SmramAtDefaultSmbase,
+                mQ35SmramAtDefaultSmbase);
+  ASSERT_RETURN_ERROR (PcdStatus);
+}
+
+
 VOID
 QemuUc32BaseInitialization (
   VOID
diff --git a/OvmfPkg/PlatformPei/Platform.c b/OvmfPkg/PlatformPei/Platform.c
index 510d6d7477ec..473af102783a 100644
--- a/OvmfPkg/PlatformPei/Platform.c
+++ b/OvmfPkg/PlatformPei/Platform.c
@@ -792,6 +792,7 @@ InitializePlatform (
   if (FeaturePcdGet (PcdSmmSmramRequire)) {
     Q35BoardVerification ();
     Q35TsegMbytesInitialization ();
+    Q35SmramAtDefaultSmbaseInitialization ();
   }
 
   PublishPeiMemory ();
-- 
2.19.1.3.g30247aa5d201



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