2 files changed, 21 insertions, 0 deletions
diff --git a/MdePkg/Include/Pi/PiHob.h b/MdePkg/Include/Pi/PiHob.h
index fc523e1e8b..b24f95149b 100644
--- a/MdePkg/Include/Pi/PiHob.h
+++ b/MdePkg/Include/Pi/PiHob.h
@@ -255,6 +255,13 @@ typedef UINT32 EFI_RESOURCE_ATTRIBUTE_TYPE;
 #define EFI_RESOURCE_ATTRIBUTE_INITIALIZED              0x00000002
 #define EFI_RESOURCE_ATTRIBUTE_TESTED                   0x00000004
 #define EFI_RESOURCE_ATTRIBUTE_READ_PROTECTED           0x00000080
+//
+// This is typically used as memory cacheability attribute today.
+// NOTE: Since PI spec 1.4, please use EFI_RESOURCE_ATTRIBUTE_READ_ONLY_PROTECTED
+// as Physical write protected attribute, and EFI_RESOURCE_ATTRIBUTE_WRITE_PROTECTED
+// means Memory cacheability attribute: The memory supports being programmed with
+// a writeprotected cacheable attribute.
+//
 #define EFI_RESOURCE_ATTRIBUTE_WRITE_PROTECTED          0x00000100
 #define EFI_RESOURCE_ATTRIBUTE_EXECUTION_PROTECTED      0x00000200
 #define EFI_RESOURCE_ATTRIBUTE_PERSISTENT               0x00800000
@@ -274,10 +281,20 @@ typedef UINT32 EFI_RESOURCE_ATTRIBUTE_TYPE;
 #define EFI_RESOURCE_ATTRIBUTE_64_BIT_IO                0x00010000
 #define EFI_RESOURCE_ATTRIBUTE_UNCACHED_EXPORTED        0x00020000
 #define EFI_RESOURCE_ATTRIBUTE_READ_PROTECTABLE         0x00100000
+//
+// This is typically used as memory cacheability attribute today.
+// NOTE: Since PI spec 1.4, please use EFI_RESOURCE_ATTRIBUTE_READ_ONLY_PROTECTABLE
+// as Memory capability attribute: The memory supports being protected from processor
+// writes, and EFI_RESOURCE_ATTRIBUTE_WRITE_PROTEC TABLE means Memory cacheability attribute:
+// The memory supports being programmed with a writeprotected cacheable attribute.
+//
 #define EFI_RESOURCE_ATTRIBUTE_WRITE_PROTECTABLE        0x00200000
 #define EFI_RESOURCE_ATTRIBUTE_EXECUTION_PROTECTABLE    0x00400000
 #define EFI_RESOURCE_ATTRIBUTE_PERSISTABLE              0x01000000
 
+#define EFI_RESOURCE_ATTRIBUTE_READ_ONLY_PROTECTED      0x00040000
+#define EFI_RESOURCE_ATTRIBUTE_READ_ONLY_PROTECTABLE    0x00800000
+
 ///
 /// Describes the resource properties of all fixed,
 /// nonrelocatable resource ranges found on the processor
diff --git a/MdePkg/Include/Uefi/UefiSpec.h b/MdePkg/Include/Uefi/UefiSpec.h
index 1c401e8e85..243f33078a 100644
--- a/MdePkg/Include/Uefi/UefiSpec.h
+++ b/MdePkg/Include/Uefi/UefiSpec.h
@@ -71,9 +71,13 @@ typedef enum {
 //
 // Physical memory protection attributes
 //
+// Note: UEFI spec 2.5 and following: use EFI_MEMORY_RO as write-protected physical memory
+// protection attribute. Also, EFI_MEMORY_WP means cacheability attribute.
+//
 #define EFI_MEMORY_WP   0x0000000000001000ULL
 #define EFI_MEMORY_RP   0x0000000000002000ULL
 #define EFI_MEMORY_XP   0x0000000000004000ULL
+#define EFI_MEMORY_RO   0x0000000000020000ULL
 //
 // Physical memory persistence attribute. 
 // The memory region supports byte-addressable non-volatility.