MdeModulePkg/PciHostBridge: Add IOMMU support.

If IOMMU protocol is installed, PciHostBridge just calls
IOMMU AllocateBuffer/FreeBuffer/Map/Unmap.

PciHostBridge does not set IOMMU access attribute,
because it does not know which device request the DMA.
This work is done by PciBus driver.

Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Cc: Leo Duran <leo.duran@amd.com>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>

Previous patch Tested-by: Brijesh Singh <brijesh.singh@amd.com>
Previous patch Tested-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Jiewen Yao <jiewen.yao@intel.com>
Reviewed-by: Ruiyu Ni <ruiyu.ni@intel.com>
Reviewed-by: Leo Duran <leo.duran@amd.com>

MdeModulePkg/Bus/Pci/PciHostBridgeDxe/PciHostBridge.c

@@ -28,6 +28,10 @@ GLOBAL_REMOVE_IF_UNREFERENCED CHAR16 *mPciResourceTypeStr[] = {
   L"I/O", L"Mem", L"PMem", L"Mem64", L"PMem64", L"Bus"
 };
 
+EDKII_IOMMU_PROTOCOL        *mIoMmuProtocol;
+EFI_EVENT                   mIoMmuEvent;
+VOID                        *mIoMmuRegistration;
+
 /**
   Ensure the compatibility of an IO space descriptor with the IO aperture.
 
@@ -312,6 +316,28 @@ FreeMemorySpaceMap:
   return Status;
 }
 
+/**
+  Event notification that is fired when IOMMU protocol is installed.
+
+  @param  Event                 The Event that is being processed.
+  @param  Context               Event Context.
+
+**/
+VOID
+EFIAPI
+IoMmuProtocolCallback (
+  IN  EFI_EVENT       Event,
+  IN  VOID            *Context
+  )
+{
+  EFI_STATUS   Status;
+
+  Status = gBS->LocateProtocol (&gEdkiiIoMmuProtocolGuid, NULL, (VOID **)&mIoMmuProtocol);
+  if (!EFI_ERROR(Status)) {
+    gBS->CloseEvent (mIoMmuEvent);
+  }
+}
+
 /**
 
   Entry point of this driver.
@@ -489,6 +515,17 @@ InitializePciHostBridge (
     ASSERT_EFI_ERROR (Status);
   }
   PciHostBridgeFreeRootBridges (RootBridges, RootBridgeCount);
+
+  if (!EFI_ERROR (Status)) {
+    mIoMmuEvent = EfiCreateProtocolNotifyEvent (
+                    &gEdkiiIoMmuProtocolGuid,
+                    TPL_CALLBACK,
+                    IoMmuProtocolCallback,
+                    NULL,
+                    &mIoMmuRegistration
+                    );
+  }
+
   return Status;
 }