diff --git a/include/mm_communication.h b/include/mm_communication.h
new file mode 100644
index 000000000000..b9bfbe4cf0a1
--- /dev/null
+++ b/include/mm_communication.h
@@ -0,0 +1,207 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ *  Headers for EFI variable service via StandAloneMM, EDK2 application running
+ *  in OP-TEE
+ *
+ *  Copyright (c) 2017, Intel Corporation. All rights reserved.
+ *  Copyright (C) 2020 Linaro Ltd. <sughosh.ganu at linaro.org>
+ *  Copyright (C) 2020 Linaro Ltd. <ilias.apalodimas at linaro.org>
+ */
+
+#ifndef _MM_VARIABLE_H_
+#define _MM_VARIABLE_H_
+
+#include <part_efi.h>
+
+/*
+ * Interface to the pseudo TA, which provides a communication channel with
+ * the StandaloneMM Secure Partition (StMM) running at S-EL0
+ */
+
+#define PTA_STMM_CMDID_COMMUNICATE 0
+
+/* OP-TEE is using big endian GUIDs while UEFI uses little endian ones */
+#define PTA_STMM_UUID { 0xed32d533, 0x99e6, 0x4209, {\
+			0x9c, 0xc0, 0x2d, 0x72, 0xcd, 0xd9, 0x98, 0xa7 } }
+
+#define EFI_MM_VARIABLE_GUID \
+	EFI_GUID(0xed32d533, 0x99e6, 0x4209, \
+		 0x9c, 0xc0, 0x2d, 0x72, 0xcd, 0xd9, 0x98, 0xa7)
+
+/* Defined in EDK2 MdePkg/Include/Protocol/MmCommunication.h */
+
+/**
+ * struct efi_mm_communicate_header - Header used for SMM variable communication
+
+ * @header_guid:  header use for disambiguation of content
+ * @message_len:  length of the message. Does not include the size of the
+ *                header
+ * @data:         payload of the message
+ *
+ * Defined in EDK2 as EFI_MM_COMMUNICATE_HEADER
+ * To avoid confusion in interpreting frames, the communication buffer should
+ * always begin with efi_mm_communicate_header
+ */
+struct efi_mm_communicate_header {
+	efi_guid_t header_guid;
+	size_t     message_len;
+	u8         data[];
+};
+
+#define MM_COMMUNICATE_HEADER_SIZE \
+	(sizeof(struct efi_mm_communicate_header))
+
+/* Defined in EDK2 ArmPkg/Include/IndustryStandard/ArmStdSmc.h */
+
+/* MM return error codes */
+#define ARM_SMC_MM_RET_SUCCESS              0
+#define ARM_SMC_MM_RET_NOT_SUPPORTED       -1
+#define ARM_SMC_MM_RET_INVALID_PARAMS      -2
+#define ARM_SMC_MM_RET_DENIED              -3
+#define ARM_SMC_MM_RET_NO_MEMORY           -4
+
+/* Defined in EDK2 MdeModulePkg/Include/Guid/SmmVariableCommon.h */
+
+#define SMM_VARIABLE_FUNCTION_GET_VARIABLE  1
+/*
+ * The payload for this function is
+ * SMM_VARIABLE_COMMUNICATE_GET_NEXT_VARIABLE_NAME.
+ */
+#define SMM_VARIABLE_FUNCTION_GET_NEXT_VARIABLE_NAME  2
+/*
+ * The payload for this function is SMM_VARIABLE_COMMUNICATE_ACCESS_VARIABLE.
+ */
+#define SMM_VARIABLE_FUNCTION_SET_VARIABLE  3
+/*
+ * The payload for this function is
+ * SMM_VARIABLE_COMMUNICATE_QUERY_VARIABLE_INFO.
+ */
+#define SMM_VARIABLE_FUNCTION_QUERY_VARIABLE_INFO  4
+/*
+ * It is a notify event, no extra payload for this function.
+ */
+#define SMM_VARIABLE_FUNCTION_READY_TO_BOOT  5
+/*
+ * It is a notify event, no extra payload for this function.
+ */
+#define SMM_VARIABLE_FUNCTION_EXIT_BOOT_SERVICE  6
+/*
+ * The payload for this function is VARIABLE_INFO_ENTRY.
+ * The GUID in EFI_SMM_COMMUNICATE_HEADER is gEfiSmmVariableProtocolGuid.
+ */
+#define SMM_VARIABLE_FUNCTION_GET_STATISTICS  7
+/*
+ * The payload for this function is SMM_VARIABLE_COMMUNICATE_LOCK_VARIABLE
+ */
+#define SMM_VARIABLE_FUNCTION_LOCK_VARIABLE   8
+
+#define SMM_VARIABLE_FUNCTION_VAR_CHECK_VARIABLE_PROPERTY_SET  9
+
+#define SMM_VARIABLE_FUNCTION_VAR_CHECK_VARIABLE_PROPERTY_GET  10
+
+#define SMM_VARIABLE_FUNCTION_GET_PAYLOAD_SIZE  11
+/*
+ * The payload for this function is
+ * SMM_VARIABLE_COMMUNICATE_RUNTIME_VARIABLE_CACHE_CONTEXT
+ */
+#define SMM_VARIABLE_FUNCTION_INIT_RUNTIME_VARIABLE_CACHE_CONTEXT 12
+
+#define SMM_VARIABLE_FUNCTION_SYNC_RUNTIME_CACHE  13
+/*
+ * The payload for this function is
+ * SMM_VARIABLE_COMMUNICATE_GET_RUNTIME_CACHE_INFO
+ */
+#define SMM_VARIABLE_FUNCTION_GET_RUNTIME_CACHE_INFO  14
+
+/**
+ * struct smm_variable_communicate_header - Used for SMM variable communication
+
+ * @function:     function to call in Smm.
+ * @ret_status:   return status
+ * @data:         payload
+ *
+ * Defined in EDK2 as SMM_VARIABLE_COMMUNICATE_HEADER
+ */
+struct smm_variable_communicate_header {
+	efi_uintn_t  function;
+	efi_status_t ret_status;
+	u8           data[];
+};
+
+#define MM_VARIABLE_COMMUNICATE_SIZE \
+	(sizeof(struct smm_variable_communicate_header))
+
+/**
+ * struct smm_variable_access - Used to communicate with StMM by
+ *                              SetVariable and GetVariable.
+
+ * @function:     vendor GUID to call in Smm
+ * @data_size:    size of EFI variable data
+ * @name_size:    size of EFI name
+ * @attr:         attributes
+ * @name:         variable name
+ *
+ * Defined in EDK2 as SMM_VARIABLE_COMMUNICATE_ACCESS_VARIABLE
+ *
+ */
+struct smm_variable_access {
+	efi_guid_t  guid;
+	efi_uintn_t data_size;
+	efi_uintn_t name_size;
+	u32         attr;
+	u16         name[];
+};
+
+#define MM_VARIABLE_ACCESS_HEADER_SIZE \
+	(sizeof(struct smm_variable_access))
+/**
+ * struct smm_variable_payload_size - Used to get the max allowed
+ *                                    payload used in StMM.
+ *
+ * @size:  size to fill in
+ *
+ * Defined in EDK2 as SMM_VARIABLE_COMMUNICATE_GET_PAYLOAD_SIZE
+ *
+ */
+struct smm_variable_payload_size {
+	efi_uintn_t size;
+};
+
+/**
+ * struct smm_variable_getnext - Used to communicate with StMM for
+ *                               GetNextVariableName.
+ *
+ * @size:       vendor GUID
+ * @name_size:  size of the name of the variable
+ * @name:       variable name
+ *
+ * Defined in EDK2 as SMM_VARIABLE_COMMUNICATE_GET_PAYLOAD_SIZE
+ */
+struct smm_variable_getnext {
+	efi_guid_t  guid;
+	efi_uintn_t name_size;
+	u16         name[];
+};
+
+#define MM_VARIABLE_GET_NEXT_HEADER_SIZE \
+	(sizeof(struct smm_variable_getnext))
+
+/**
+ * struct smm_variable_query_info - Used to communicate with StMM for
+ *                                  QueryVariableInfo.
+ *
+ * @max_variable_storage:        max available storage
+ * @remaining_variable_storage:  remaining available storage
+ * @max_variable_size:           max variable supported size
+ * @attr:                        attributes to query storage for
+ *
+ * Defined in EDK2 as SMM_VARIABLE_COMMUNICATE_GET_PAYLOAD_SIZE
+ */
+struct smm_variable_query_info {
+	u64 max_variable_storage;
+	u64 remaining_variable_storage;
+	u64 max_variable_size;
+	u32 attr;
+};
+
+#endif /* _MM_VARIABLE_H_ */
