diff --git a/realm/aarch64/realm_entrypoint.S b/realm/aarch64/realm_entrypoint.S
new file mode 100644
index 0000000..97c4ff5
--- /dev/null
+++ b/realm/aarch64/realm_entrypoint.S
@@ -0,0 +1,79 @@
+/*
+ * Copyright (c) 2022, Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <arch.h>
+#include <asm_macros.S>
+#include <realm_def.h>
+
+	.globl	realm_entrypoint
+
+.section .bss.stacks
+	.fill	REALM_STACK_SIZE
+stacks_end:
+
+func realm_entrypoint
+	/* Setup the stack pointer. */
+	adr	x1, stacks_end
+	mov	sp, x1
+
+	/* Clear BSS */
+	ldr	x0, =__REALM_BSS_START__
+	adr	x1, realm_entrypoint
+	add	x0, x1, x0
+	ldr	x1, =__REALM_BSS_SIZE__
+	bl	zeromem16
+
+	/*
+	 * Invalidate the data cache for the whole Realm.
+	 * This prevents re-use of stale data cache entries from
+	 * prior bootloader stages.
+	 */
+	adrp	x0, __REALM_TEXT_START__
+	add	x0, x0, realm_entrypoint
+	adrp	x1, __REALM_BSS_END__
+	add	x1, x1, realm_entrypoint
+	sub	x1, x1, x0
+	bl	inv_dcache_range
+
+	/* Initialize architectural state. */
+	bl	arch_init
+
+	/* Relocate symbols */
+pie_fixup:
+	ldr	x0, =pie_fixup
+	and	x0, x0, #~(PAGE_ALIGNMENT - 1)
+	mov	x1, REALM_MAX_LOAD_IMG_SIZE
+	add	x1, x1, x0
+	bl	fixup_gdt_reloc
+
+	/* And jump to the C entrypoint. */
+	b	realm_payload_main
+endfunc realm_entrypoint
+
+/* Initialize architectural state. */
+func arch_init
+	/* Set the exception vectors. */
+	adr	x0, realm_vector
+	add	x1, x1, :lo12:realm_vector
+	msr	vbar_el1, x0
+	isb
+
+	/* Enable the instruction cache and stack pointer alignment checks. */
+	mov_imm	x0, (SCTLR_EL1_RES1 | SCTLR_I_BIT | SCTLR_A_BIT | SCTLR_SA_BIT)
+	msr	sctlr_el1, x0
+
+	/*
+	 * Set CPACR_EL1.FPEN=11 no EL1/0 trapping of
+	 * SVE/Adv. SIMD/FP instructions.
+	 */
+	mov	x1, CPACR_EL1_FPEN(CPACR_EL1_FP_TRAP_NONE)
+	mrs	x0, cpacr_el1
+	orr	x0, x0, x1
+	msr	cpacr_el1, x0
+	isb
+
+	ret
+endfunc arch_init
diff --git a/realm/aarch64/realm_exceptions.S b/realm/aarch64/realm_exceptions.S
new file mode 100644
index 0000000..6ce8810
--- /dev/null
+++ b/realm/aarch64/realm_exceptions.S
@@ -0,0 +1,140 @@
+/*
+ * Copyright (c) 2022, Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <asm_macros.S>
+
+	.globl	realm_vector
+
+/*
+ * Exception vector code for unhandled exceptions.
+ * Print a crash dump on the UART and loops forever.
+ */
+.macro unhandled_exception name
+	vector_entry \name
+	b crash_dump
+	end_vector_entry \name
+.endm
+
+vector_base realm_vector
+
+	/*
+	 * Current EL with SP0 : 0x0 - 0x200.
+	 */
+unhandled_exception sync_sp0
+unhandled_exception irq_sp0
+unhandled_exception fiq_sp0
+unhandled_exception serr_sp0
+
+	/*
+	 * Current EL with SPx : 0x200 - 0x400.
+	 */
+vector_entry sync_spx
+	b	sync_exception_vector_entry
+end_vector_entry sync_spx
+
+vector_entry irq_spx
+	b	interrupt_vector_entry
+end_vector_entry irq_spx
+
+vector_entry fiq_spx
+	b	interrupt_vector_entry
+end_vector_entry fiq_spx
+
+unhandled_exception serr_spx
+
+	/*
+	 * Lower EL using AArch64 : 0x400 - 0x600.
+	 */
+unhandled_exception sync_a64
+unhandled_exception irq_a64
+unhandled_exception fiq_a64
+unhandled_exception serr_a64
+
+	/*
+	 * Lower EL using AArch32 : 0x600 - 0x800.
+	 */
+unhandled_exception sync_a32
+unhandled_exception irq_a32
+unhandled_exception fiq_a32
+unhandled_exception serr_a32
+
+.macro save_gp_regs
+	stp	x0, x1, [sp, #0x0]
+	stp	x2, x3, [sp, #0x10]
+	stp	x4, x5, [sp, #0x20]
+	stp	x6, x7, [sp, #0x30]
+	stp	x8, x9, [sp, #0x40]
+	stp	x10, x11, [sp, #0x50]
+	stp	x12, x13, [sp, #0x60]
+	stp	x14, x15, [sp, #0x70]
+	stp	x16, x17, [sp, #0x80]
+	stp	x18, x19, [sp, #0x90]
+	stp	x20, x21, [sp, #0xa0]
+	stp	x22, x23, [sp, #0xb0]
+	stp	x24, x25, [sp, #0xc0]
+	stp	x26, x27, [sp, #0xd0]
+	stp	x28, x29, [sp, #0xe0]
+	/* We push xzr simply to keep the stack 16-byte aligned. */
+	stp	x30, xzr, [sp, #0xf0]
+.endm
+
+.macro restore_gp_regs
+	ldp	x30, xzr, [sp, #0xf0]
+	ldp	x28, x29, [sp, #0xe0]
+	ldp	x26, x27, [sp, #0xd0]
+	ldp	x24, x25, [sp, #0xc0]
+	ldp	x22, x23, [sp, #0xb0]
+	ldp	x20, x21, [sp, #0xa0]
+	ldp	x18, x19, [sp, #0x90]
+	ldp	x16, x17, [sp, #0x80]
+	ldp	x14, x15, [sp, #0x70]
+	ldp	x12, x13, [sp, #0x60]
+	ldp	x10, x11, [sp, #0x50]
+	ldp	x8, x9, [sp, #0x40]
+	ldp	x6, x7, [sp, #0x30]
+	ldp	x4, x5, [sp, #0x20]
+	ldp	x2, x3, [sp, #0x10]
+	ldp	x0, x1, [sp, #0x0]
+.endm
+
+func sync_exception_vector_entry
+	sub	sp, sp, #0x100
+	save_gp_regs
+	mov	x19, sp
+	bl	tftf_sync_exception_handler
+	cbnz	x0, 0f
+	mov x0, x19
+	/* Save original stack pointer value on the stack */
+	add	x1, x0, #0x100
+	str	x1, [x0, #0xf8]
+	b print_exception
+0:	restore_gp_regs
+	add	sp, sp, #0x100
+	eret
+endfunc sync_exception_vector_entry
+
+func interrupt_vector_entry
+	sub	sp, sp, #0x100
+	save_gp_regs
+	bl	realm_interrupt_handler
+	restore_gp_regs
+	add	sp, sp, #0x100
+	eret
+endfunc interrupt_vector_entry
+
+func crash_dump
+	/* Save general-purpose registers on the stack. */
+	sub	sp, sp, #0x100
+	save_gp_regs
+
+	/* Save original stack pointer value on the stack. */
+	add	x1, sp, #0x100
+	str	x1, [sp, #0xf8]
+
+	/* Print the saved CPU context on the UART. */
+	mov	x0, sp
+	b	print_exception
+endfunc crash_dump
diff --git a/realm/platform.h b/realm/platform.h
new file mode 100644
index 0000000..2c6ad27
--- /dev/null
+++ b/realm/platform.h
@@ -0,0 +1,20 @@
+/*
+ * Copyright (c) 2022, Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ *
+ */
+
+#ifndef REALM_PLATFORM_H
+#define REALM_PLATFORM_H
+
+/*
+ * Helper that returns a linear core ID from a MPID
+ * Need to provide a RSI_HOST_CALL to request this from Host platform.
+ */
+unsigned int platform_get_core_pos(u_register_t mpid)
+{
+	return 0U;
+}
+
+#endif /* REALM_PLATFORM_H */
diff --git a/realm/realm.ld.S b/realm/realm.ld.S
new file mode 100644
index 0000000..ca3b809
--- /dev/null
+++ b/realm/realm.ld.S
@@ -0,0 +1,79 @@
+/*
+ * Copyright (c) 2022, Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+
+ENTRY(realm_entrypoint)
+
+#include <realm_def.h>
+
+MEMORY {
+
+    RAM (rwx): ORIGIN = 0x0, LENGTH = REALM_MAX_LOAD_IMG_SIZE
+}
+
+SECTIONS
+{
+     ASSERT(. == ALIGN(PAGE_SIZE),
+           "TEXT_START address is not aligned to PAGE_SIZE.")
+    .text : {
+        __REALM_TEXT_START__ = .;
+        *realm_entrypoint.o(.text*)
+        *(.text*)
+        *(.vectors)
+        . = NEXT(PAGE_SIZE);
+        __REALM_TEXT_END__ = .;
+    }> RAM
+
+    .rodata : {
+        . = ALIGN(PAGE_SIZE);
+        __REALM_RODATA_START__ = .;
+        *(.rodata*)
+
+        /*
+         * Keep the .got section in the RO section as it is patched
+         * prior to enabling the MMU and having the .got in RO is better for
+         * security. GOT is a table of addresses so ensure 8-byte alignment.
+         */
+        . = ALIGN(8);
+        __GOT_START__ = .;
+        *(.got)
+        __GOT_END__ = .;
+
+        . = NEXT(PAGE_SIZE);
+        __REALM_RODATA_END__ = .;
+
+    }> RAM
+
+    .data : {
+        . = ALIGN(PAGE_SIZE);
+        __REALM_DATA_START__ = .;
+        *(.data*)
+        . = ALIGN(PAGE_SIZE);
+        . = NEXT(PAGE_SIZE);
+        __REALM_DATA_END__ = .;
+    }> RAM
+
+    /*
+     * .rela.dyn needs to come after .data for the read-elf utility to parse
+     * this section correctly. Ensure 8-byte alignment so that the fields of
+     * RELA data structure are aligned.
+     */
+    . = ALIGN(8);
+    __RELA_START__ = .;
+    .rela.dyn . : {
+    }> RAM
+    __RELA_END__ = .;
+
+    .bss (NOLOAD) : {
+        . = ALIGN(PAGE_SIZE);
+        __REALM_BSS_START__ = .;
+        *(SORT_BY_ALIGNMENT(.bss*))
+        *(COMMON)
+        . = NEXT(PAGE_SIZE);
+        __REALM_BSS_END__ = .;
+    }> RAM
+    __REALM_BSS_SIZE__ = SIZEOF(.bss);
+}
diff --git a/realm/realm.mk b/realm/realm.mk
new file mode 100644
index 0000000..638f02e
--- /dev/null
+++ b/realm/realm.mk
@@ -0,0 +1,54 @@
+#
+# Copyright (c) 2022, Arm Limited. All rights reserved.
+#
+# SPDX-License-Identifier: BSD-3-Clause
+#
+
+include branch_protection.mk
+
+REALM_INCLUDES :=							\
+	-Itftf/framework/include					\
+	-Iinclude							\
+	-Iinclude/common						\
+	-Iinclude/common/${ARCH}					\
+	-Iinclude/lib							\
+	-Iinclude/lib/${ARCH}						\
+	-Iinclude/lib/utils						\
+	-Iinclude/lib/xlat_tables					\
+	-Iinclude/runtime_services					\
+	-Iinclude/runtime_services/host_realm_managment			\
+	-Irealm								\
+	-Irealm/aarch64
+
+REALM_SOURCES:=								\
+	$(addprefix realm/,						\
+	aarch64/realm_entrypoint.S					\
+	aarch64/realm_exceptions.S					\
+	realm_debug.c							\
+	realm_payload_main.c						\
+	realm_interrupt.c						\
+	realm_rsi.c							\
+	realm_shared_data.c						\
+	)
+
+REALM_SOURCES += lib/${ARCH}/cache_helpers.S				\
+	lib/${ARCH}/misc_helpers.S					\
+	lib/smc/${ARCH}/asm_smc.S					\
+	lib/smc/${ARCH}/smc.c						\
+	lib/exceptions/${ARCH}/sync.c					\
+	lib/locks/${ARCH}/spinlock.S					\
+	lib/delay/delay.c
+
+# TODO: Remove dependency on TFTF files.
+REALM_SOURCES	+=							\
+	tftf/framework/${ARCH}/exception_report.c
+
+REALM_LINKERFILE:=	realm/realm.ld.S
+
+REALM_DEFINES:=
+$(eval $(call add_define,REALM_DEFINES,ARM_ARCH_MAJOR))
+$(eval $(call add_define,REALM_DEFINES,ARM_ARCH_MINOR))
+$(eval $(call add_define,REALM_DEFINES,ENABLE_BTI))
+$(eval $(call add_define,REALM_DEFINES,ENABLE_PAUTH))
+$(eval $(call add_define,REALM_DEFINES,LOG_LEVEL))
+$(eval $(call add_define,REALM_DEFINES,IMAGE_REALM))
diff --git a/realm/realm_debug.c b/realm/realm_debug.c
new file mode 100644
index 0000000..e9eb61e
--- /dev/null
+++ b/realm/realm_debug.c
@@ -0,0 +1,63 @@
+/*
+ * Copyright (c) 2022, Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <stdarg.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <string.h>
+
+#include <arch_helpers.h>
+#include <host_shared_data.h>
+
+/*
+ * A printf formatted function used in the Realm world to log messages
+ * in the shared buffer.
+ * Locate the shared logging buffer and print its content
+ */
+void realm_printf(const char *fmt, ...)
+{
+	host_shared_data_t *guest_shared_data = realm_get_shared_structure();
+	char *log_buffer = (char *)guest_shared_data->log_buffer;
+	va_list args;
+
+	va_start(args, fmt);
+	spin_lock((spinlock_t *)&guest_shared_data->printf_lock);
+	if (strnlen((const char *)log_buffer, MAX_BUF_SIZE) == MAX_BUF_SIZE) {
+		(void)memset((char *)log_buffer, 0, MAX_BUF_SIZE);
+	}
+	(void)vsnprintf((char *)log_buffer +
+			strnlen((const char *)log_buffer, MAX_BUF_SIZE),
+			MAX_BUF_SIZE, fmt, args);
+	spin_unlock((spinlock_t *)&guest_shared_data->printf_lock);
+	va_end(args);
+}
+
+void __attribute__((__noreturn__)) do_panic(const char *file, int line)
+{
+	realm_printf("PANIC in file: %s line: %d\n", file, line);
+	while (true) {
+		continue;
+	}
+}
+
+/* This is used from printf() when crash dump is reached */
+int console_putc(int c)
+{
+	host_shared_data_t *guest_shared_data = realm_get_shared_structure();
+	char *log_buffer = (char *)guest_shared_data->log_buffer;
+
+	if ((c < 0) || (c > 127)) {
+		return -1;
+	}
+	spin_lock((spinlock_t *)&guest_shared_data->printf_lock);
+	if (strnlen((const char *)log_buffer, MAX_BUF_SIZE) == MAX_BUF_SIZE) {
+		(void)memset((char *)log_buffer, 0, MAX_BUF_SIZE);
+	}
+	*((char *)log_buffer + strnlen((const char *)log_buffer, MAX_BUF_SIZE)) = c;
+	spin_unlock((spinlock_t *)&guest_shared_data->printf_lock);
+
+	return c;
+}
diff --git a/realm/realm_interrupt.c b/realm/realm_interrupt.c
new file mode 100644
index 0000000..02ab55c
--- /dev/null
+++ b/realm/realm_interrupt.c
@@ -0,0 +1,13 @@
+/*
+ * Copyright (c) 2022, Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <debug.h>
+
+/* dummy interrupt handler as for now*/
+void realm_interrupt_handler(void)
+{
+	INFO("%s\n", __func__);
+}
diff --git a/realm/realm_payload_main.c b/realm/realm_payload_main.c
new file mode 100644
index 0000000..bd4dec7
--- /dev/null
+++ b/realm/realm_payload_main.c
@@ -0,0 +1,85 @@
+/*
+ * Copyright (c) 2022, Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ *
+ */
+
+#include <stdio.h>
+
+#include <debug.h>
+#include <host_realm_helper.h>
+#include <host_shared_data.h>
+#include "realm_def.h"
+#include <realm_rsi.h>
+#include <tftf_lib.h>
+
+/*
+ * This function reads sleep time in ms from shared buffer and spins PE in a loop
+ * for that time period.
+ */
+static void realm_sleep_cmd(void)
+{
+	uint64_t sleep = realm_shared_data_get_host_val(HOST_SLEEP_INDEX);
+
+	INFO("REALM_PAYLOAD: Realm payload going to sleep for %llums\n", sleep);
+	waitms(sleep);
+}
+
+/*
+ * This function requests RSI/ABI version from RMM.
+ */
+static void realm_get_rsi_version(void)
+{
+	u_register_t version;
+
+	version = rsi_get_version();
+	if (version == (u_register_t)SMC_UNKNOWN) {
+		ERROR("SMC_RSI_ABI_VERSION failed (%ld)", (long)version);
+		return;
+	}
+
+	INFO("RSI ABI version %u.%u (expected: %u.%u)",
+	RSI_ABI_VERSION_GET_MAJOR(version),
+	RSI_ABI_VERSION_GET_MINOR(version),
+	RSI_ABI_VERSION_GET_MAJOR(RSI_ABI_VERSION),
+	RSI_ABI_VERSION_GET_MINOR(RSI_ABI_VERSION));
+}
+
+/*
+ * This is the entry function for Realm payload, it first requests the shared buffer
+ * IPA address from Host using HOST_CALL/RSI, it reads the command to be executed,
+ * performs the request, and returns to Host with the execution state SUCCESS/FAILED
+ *
+ * Host in NS world requests Realm to execute certain operations using command
+ * depending on the test case the Host wants to perform.
+ */
+void realm_payload_main(void)
+{
+	uint8_t cmd = 0U;
+	bool test_succeed = false;
+
+	realm_set_shared_structure((host_shared_data_t *)rsi_get_ns_buffer());
+	if (realm_get_shared_structure() != NULL) {
+		cmd = realm_shared_data_get_realm_cmd();
+		switch (cmd) {
+		case REALM_SLEEP_CMD:
+			realm_sleep_cmd();
+			test_succeed = true;
+			break;
+		case REALM_GET_RSI_VERSION:
+			realm_get_rsi_version();
+			test_succeed = true;
+			break;
+		default:
+			INFO("REALM_PAYLOAD: %s invalid cmd=%hhu", __func__, cmd);
+			break;
+		}
+	}
+
+	if (test_succeed) {
+		rsi_exit_to_host(HOST_CALL_EXIT_SUCCESS_CMD);
+	} else {
+		rsi_exit_to_host(HOST_CALL_EXIT_FAILED_CMD);
+	}
+}
diff --git a/realm/realm_rsi.c b/realm/realm_rsi.c
new file mode 100644
index 0000000..c805514
--- /dev/null
+++ b/realm/realm_rsi.c
@@ -0,0 +1,47 @@
+
+/*
+ * Copyright (c) 2022, Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ *
+ */
+
+#include <host_realm_rmi.h>
+#include <lib/aarch64/arch_features.h>
+#include <realm_rsi.h>
+#include <smccc.h>
+
+static struct rsi_host_call host_cal __aligned(sizeof(struct rsi_host_call));
+
+/* This function return RSI_ABI_VERSION */
+u_register_t rsi_get_version(void)
+{
+	smc_ret_values res = {};
+
+	res = tftf_smc(&(smc_args)
+		{RSI_ABI_VERSION, 0UL, 0UL, 0UL, 0UL, 0UL, 0UL, 0UL});
+
+	return res.ret0;
+}
+
+/* This function will call the Host to request IPA of the NS shared buffer */
+u_register_t rsi_get_ns_buffer(void)
+{
+	smc_ret_values res = {};
+
+	host_cal.imm = HOST_CALL_GET_SHARED_BUFF_CMD;
+	res = tftf_smc(&(smc_args) {RSI_HOST_CALL, (u_register_t)&host_cal,
+		0UL, 0UL, 0UL, 0UL, 0UL, 0UL});
+	if (res.ret0 != RSI_SUCCESS) {
+		return 0U;
+	}
+	return host_cal.gprs[0];
+}
+
+/* This function call Host and request to exit Realm with proper exit code */
+void rsi_exit_to_host(enum host_call_cmd exit_code)
+{
+	host_cal.imm = exit_code;
+	tftf_smc(&(smc_args) {RSI_HOST_CALL, (u_register_t)&host_cal,
+		0UL, 0UL, 0UL, 0UL, 0UL, 0UL});
+}
diff --git a/realm/realm_rsi.h b/realm/realm_rsi.h
new file mode 100644
index 0000000..34721cd
--- /dev/null
+++ b/realm/realm_rsi.h
@@ -0,0 +1,117 @@
+/*
+ * Copyright (c) 2022, Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ *
+ */
+
+#ifndef REALM_RSI_H
+#define REALM_RSI_H
+
+#include <stdint.h>
+#include <tftf_lib.h>
+
+#define SMC_RSI_CALL_BASE	0xC4000190
+#define SMC_RSI_FID(_x)		(SMC_RSI_CALL_BASE + (_x))
+/*
+ * This file describes the Realm Services Interface (RSI) Application Binary
+ * Interface (ABI) for SMC calls made from within the Realm to the RMM and
+ * serviced by the RMM.
+ *
+ * See doc/rmm_interface.md for more details.
+ */
+
+/*
+ * The major version number of the RSI implementation.  Increase this whenever
+ * the binary format or semantics of the SMC calls change.
+ */
+#define RSI_ABI_VERSION_MAJOR		12U
+
+/*
+ * The minor version number of the RSI implementation.  Increase this when
+ * a bug is fixed, or a feature is added without breaking binary compatibility.
+ */
+#define RSI_ABI_VERSION_MINOR		0U
+
+#define RSI_ABI_VERSION_VAL		((RSI_ABI_VERSION_MAJOR << 16U) | \
+					 RSI_ABI_VERSION_MINOR)
+
+#define RSI_ABI_VERSION_GET_MAJOR(_version) ((_version) >> 16U)
+#define RSI_ABI_VERSION_GET_MINOR(_version) ((_version) & 0xFFFFU)
+
+
+/* RSI Status code enumeration as per Section D4.3.6 of the RMM Spec */
+typedef enum {
+	/* Command completed successfully */
+	RSI_SUCCESS = 0U,
+
+	/*
+	 * The value of a command input value
+	 * caused the command to fail
+	 */
+	RSI_ERROR_INPUT	= 1U,
+
+	/*
+	 * The state of the current Realm or current REC
+	 * does not match the state expected by the command
+	 */
+	RSI_ERROR_STATE	= 2U,
+
+	/* The operation requested by the command is not complete */
+	RSI_INCOMPLETE = 3U,
+
+	RSI_ERROR_COUNT
+} rsi_status_t;
+
+enum host_call_cmd {
+	HOST_CALL_GET_SHARED_BUFF_CMD = 1U,
+	HOST_CALL_EXIT_SUCCESS_CMD,
+	HOST_CALL_EXIT_FAILED_CMD
+};
+
+struct rsi_realm_config {
+	/* IPA width in bits */
+	SET_MEMBER(unsigned long ipa_width, 0, 0x1000);	/* Offset 0 */
+};
+
+/*
+ * arg0 == IPA address of target region
+ * arg1 == Size of target region in bytes
+ * arg2 == RIPAS value
+ * ret0 == Status / error
+ * ret1 == Top of modified IPA range
+ */
+
+#define RSI_HOST_CALL_NR_GPRS		7U
+
+struct rsi_host_call {
+	SET_MEMBER(struct {
+		/* Immediate value */
+		unsigned int imm;		/* Offset 0 */
+		/* Registers */
+		unsigned long gprs[RSI_HOST_CALL_NR_GPRS];
+		}, 0, 0x100);
+};
+
+/*
+ * arg0 == struct rsi_host_call addr
+ */
+#define RSI_HOST_CALL		SMC_RSI_FID(9U)
+
+
+#define RSI_ABI_VERSION		SMC_RSI_FID(0U)
+/*
+ * arg0 == struct rsi_realm_config address
+ */
+#define RSI_REALM_CONFIG	SMC_RSI_FID(6U)
+
+/* This function return RSI_ABI_VERSION */
+u_register_t rsi_get_version(void);
+
+/* This function will call the Host to request IPA of the NS shared buffer */
+u_register_t rsi_get_ns_buffer(void);
+
+/* This function call Host and request to exit Realm with proper exit code */
+void rsi_exit_to_host(enum host_call_cmd exit_code);
+
+#endif /* REALM_RSI_H */
diff --git a/realm/realm_shared_data.c b/realm/realm_shared_data.c
new file mode 100644
index 0000000..da09b53
--- /dev/null
+++ b/realm/realm_shared_data.c
@@ -0,0 +1,49 @@
+/*
+ * Copyright (c) 2022, Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <string.h>
+#include <host_shared_data.h>
+
+/**
+ *   @brief    - Returns the base address of the shared region
+ *   @param    - Void
+ *   @return   - Base address of the shared region
+ **/
+
+static host_shared_data_t *guest_shared_data;
+
+/*
+ * Set guest mapped shared buffer pointer
+ */
+void realm_set_shared_structure(host_shared_data_t *ptr)
+{
+	guest_shared_data = ptr;
+}
+
+/*
+ * Get guest mapped shared buffer pointer
+ */
+host_shared_data_t *realm_get_shared_structure(void)
+{
+	return guest_shared_data;
+}
+
+/*
+ * Return Host's data at index
+ */
+u_register_t realm_shared_data_get_host_val(uint8_t index)
+{
+	return guest_shared_data->host_param_val[(index >= MAX_DATA_SIZE) ?
+		(MAX_DATA_SIZE - 1) : index];
+}
+
+/*
+ * Get command sent from Host to realm
+ */
+uint8_t realm_shared_data_get_realm_cmd(void)
+{
+	return guest_shared_data->realm_cmd;
+}