diff --git a/xen/arch/arm/tee/ffa.c b/xen/arch/arm/tee/ffa.c
index 4b283a4de5..0026ac9134 100644
--- a/xen/arch/arm/tee/ffa.c
+++ b/xen/arch/arm/tee/ffa.c
@@ -195,6 +195,14 @@ static void handle_msg_send_direct_req(struct cpu_user_regs *regs, uint32_t fid)
         goto out;
     }
 
+    /* we do not support direct messages to VMs */
+    if ( !FFA_ID_IS_SECURE(src_dst & GENMASK(15,0)) )
+    {
+        resp.a0 = FFA_ERROR;
+        resp.a2 = FFA_RET_NOT_SUPPORTED;
+        goto out;
+    }
+
     arg.a1 = src_dst;
     arg.a2 = get_user_reg(regs, 2) & mask;
     arg.a3 = get_user_reg(regs, 3) & mask;
@@ -391,11 +399,15 @@ static int ffa_domain_init(struct domain *d)
 
     if ( !ffa_fw_version )
         return -ENODEV;
-     /*
-      * We can't use that last possible domain ID or ffa_get_vm_id() would
-      * cause an overflow.
-      */
-    if ( d->domain_id >= UINT16_MAX)
+    /*
+     * We are using the domain_id + 1 as the FF-A ID for VMs as FF-A ID 0 is
+     * reserved for the hypervisor and we only support secure endpoints using
+     * FF-A IDs with BIT 15 set to 1 so make sure those are not used by Xen.
+     */
+    BUILD_BUG_ON(DOMID_FIRST_RESERVED >= UINT16_MAX);
+    BUILD_BUG_ON((DOMID_MASK & BIT(15, U)) != 0);
+
+    if ( d->domain_id >= DOMID_FIRST_RESERVED )
         return -ERANGE;
 
     ctx = xzalloc(struct ffa_ctx);
diff --git a/xen/arch/arm/tee/ffa_partinfo.c b/xen/arch/arm/tee/ffa_partinfo.c
index 75a073d090..74324e1d9d 100644
--- a/xen/arch/arm/tee/ffa_partinfo.c
+++ b/xen/arch/arm/tee/ffa_partinfo.c
@@ -169,14 +169,23 @@ void ffa_handle_partition_info_get(struct cpu_user_regs *regs)
 
     if ( ffa_sp_count > 0 )
     {
-        uint32_t n;
+        uint32_t n, n_limit = ffa_sp_count;
         void *src_buf = ffa_rx;
 
         /* copy the secure partitions info */
-        for ( n = 0; n < ffa_sp_count; n++ )
+        for ( n = 0; n < n_limit; n++ )
         {
-            memcpy(dst_buf, src_buf, dst_size);
-            dst_buf += dst_size;
+            struct ffa_partition_info_1_1 *fpi = src_buf;
+
+            /* filter out SP not following bit 15 convention if any */
+            if ( FFA_ID_IS_SECURE(fpi->id) )
+            {
+                memcpy(dst_buf, src_buf, dst_size);
+                dst_buf += dst_size;
+            }
+            else
+                ffa_sp_count--;
+
             src_buf += src_size;
         }
     }
@@ -276,10 +285,25 @@ static bool init_subscribers(uint16_t count, uint32_t fpi_size)
     {
         fpi = ffa_rx + n * fpi_size;
 
-        if ( fpi->partition_properties & FFA_PART_PROP_NOTIF_CREATED )
-            subscr_vm_created_count++;
-        if ( fpi->partition_properties & FFA_PART_PROP_NOTIF_DESTROYED )
-            subscr_vm_destroyed_count++;
+        /*
+         * We need to have secure partitions using bit 15 set convention for
+         * secure partition IDs.
+         * Inform the user with a log and discard giving created or destroy
+         * event to those IDs.
+         */
+        if ( !FFA_ID_IS_SECURE(fpi->id) )
+        {
+            printk(XENLOG_ERR "ffa: Firmware is not using bit 15 convention for IDs !!\n"
+                              "ffa: Secure partition with id 0x%04x cannot be used\n",
+                              fpi->id);
+        }
+        else
+        {
+            if ( fpi->partition_properties & FFA_PART_PROP_NOTIF_CREATED )
+                subscr_vm_created_count++;
+            if ( fpi->partition_properties & FFA_PART_PROP_NOTIF_DESTROYED )
+                subscr_vm_destroyed_count++;
+        }
     }
 
     if ( subscr_vm_created_count )
@@ -299,10 +323,13 @@ static bool init_subscribers(uint16_t count, uint32_t fpi_size)
     {
         fpi = ffa_rx + n * fpi_size;
 
-        if ( fpi->partition_properties & FFA_PART_PROP_NOTIF_CREATED )
-            subscr_vm_created[c_pos++] = fpi->id;
-        if ( fpi->partition_properties & FFA_PART_PROP_NOTIF_DESTROYED )
-            subscr_vm_destroyed[d_pos++] = fpi->id;
+        if ( FFA_ID_IS_SECURE(fpi->id) )
+        {
+            if ( fpi->partition_properties & FFA_PART_PROP_NOTIF_CREATED )
+                subscr_vm_created[c_pos++] = fpi->id;
+            if ( fpi->partition_properties & FFA_PART_PROP_NOTIF_DESTROYED )
+                subscr_vm_destroyed[d_pos++] = fpi->id;
+        }
     }
 
     return true;
diff --git a/xen/arch/arm/tee/ffa_private.h b/xen/arch/arm/tee/ffa_private.h
index e5bc73f903..afe69b43db 100644
--- a/xen/arch/arm/tee/ffa_private.h
+++ b/xen/arch/arm/tee/ffa_private.h
@@ -108,6 +108,13 @@
  */
 #define FFA_CTX_TEARDOWN_DELAY          SECONDS(1)
 
+/*
+ * We rely on the convention suggested but not mandated by the FF-A
+ * specification that secure world endpoint identifiers have the bit 15
+ * set and normal world have it set to 0.
+ */
+#define FFA_ID_IS_SECURE(id)    ((id) & BIT(15, U))
+
 /* FF-A-1.1-REL0 section 10.9.2 Memory region handle, page 167 */
 #define FFA_HANDLE_HYP_FLAG             BIT(63, ULL)
 #define FFA_HANDLE_INVALID              0xffffffffffffffffULL
diff --git a/xen/arch/arm/tee/ffa_shm.c b/xen/arch/arm/tee/ffa_shm.c
index efa5b67db8..29675f9ba3 100644
--- a/xen/arch/arm/tee/ffa_shm.c
+++ b/xen/arch/arm/tee/ffa_shm.c
@@ -469,6 +469,7 @@ void ffa_handle_mem_share(struct cpu_user_regs *regs)
     int ret = FFA_RET_DENIED;
     uint32_t range_count;
     uint32_t region_offs;
+    uint16_t dst_id;
 
     if ( !ffa_fw_supports_fid(FFA_MEM_SHARE_64) )
     {
@@ -537,6 +538,15 @@ void ffa_handle_mem_share(struct cpu_user_regs *regs)
         goto out_unlock;
 
     mem_access = ctx->tx + trans.mem_access_offs;
+
+    dst_id = ACCESS_ONCE(mem_access->access_perm.endpoint_id);
+    if ( !FFA_ID_IS_SECURE(dst_id) )
+    {
+        /* we do not support sharing with VMs */
+        ret = FFA_RET_NOT_SUPPORTED;
+        goto out_unlock;
+    }
+
     if ( ACCESS_ONCE(mem_access->access_perm.perm) != FFA_MEM_ACC_RW )
     {
         ret = FFA_RET_NOT_SUPPORTED;
@@ -567,7 +577,7 @@ void ffa_handle_mem_share(struct cpu_user_regs *regs)
         goto out_unlock;
     }
     shm->sender_id = trans.sender_id;
-    shm->ep_id = ACCESS_ONCE(mem_access->access_perm.endpoint_id);
+    shm->ep_id = dst_id;
 
     /*
      * Check that the Composite memory region descriptor fits.