PrmPkg: Don't Set Access Attributes of Runtime MMIO Ranges

Passing in access attributes to SetMemorySpaceAttributes() will cause
the existing attributes to be overwritten. The MMIO region should have
the appropriate attributes applied during memory protection
initialization and the attributes of the memory space descriptor are
inaccurate. Don't pass in any CPU arch attributes so
SetMemorySpaceAttributes() doesn't subsequently call
gCpu->SetMemoryAttributes().

Signed-off-by: Oliver Smith-Denny <[email protected]>

PrmPkg/PrmConfigDxe/PrmConfigDxe.c

@@ -152,10 +152,15 @@ SetRuntimeMemoryRangeAttributes (
       continue;
     }
 
+    // The memory space descriptor access attributes are not accurate. Don't pass
+    // in access attributes so SetMemorySpaceAttributes() doesn't update them.
+    // EFI_MEMORY_RUNTIME is not a CPU arch attribute, so calling
+    // SetMemorySpaceAttributes() with only it set will not clear existing page table
+    // attributes for this region, such as EFI_MEMORY_XP
     Status = gDS->SetMemorySpaceAttributes (
                     RuntimeMmioRanges->Range[Index].PhysicalBaseAddress,
                     (UINT64)RuntimeMmioRanges->Range[Index].Length,
-                    Descriptor.Attributes | EFI_MEMORY_RUNTIME
+                    EFI_MEMORY_RUNTIME
                     );
     ASSERT_EFI_ERROR (Status);
     if (EFI_ERROR (Status)) {