diff --git a/misc/config_tools/library/common.py b/misc/config_tools/library/common.py
index 9c9d9c62e..db414e56c 100644
--- a/misc/config_tools/library/common.py
+++ b/misc/config_tools/library/common.py
@@ -45,7 +45,8 @@ MAX_VM_NUM = 16
 MAX_VUART_NUM = 8
 
 HV_BASE_RAM_SIZE = 0x1400000
-VM_RAM_SIZE = 0x2800000
+VM_RAM_SIZE = 0x400000
+TRUSTY_RAM_SIZE = 0x1000000
 
 class MultiItem():
 
diff --git a/misc/config_tools/schema/config.xsd b/misc/config_tools/schema/config.xsd
index 09c779899..d8a550ec6 100644
--- a/misc/config_tools/schema/config.xsd
+++ b/misc/config_tools/schema/config.xsd
@@ -412,9 +412,9 @@ These settings can only be changed at build time.</xs:documentation>
         </xs:restriction>
       </xs:simpleType>
     </xs:element>
-    <xs:element name="secure_world_support" type="Boolean" default="n" minOccurs="0">
-      <xs:annotation acrn:views="">
-        <xs:documentation>Specify secure world support for trusty OS.</xs:documentation>
+    <xs:element name="secure_world_support" type="Boolean" default="n">
+      <xs:annotation acrn:title="Enable secure world for running Trusty" acrn:views="advanced" acrn:applicable-vms="post-launched">
+        <xs:documentation>Enable secure world for this VM to provide an isolated execution environment which is suitable for running Trusted Execution Environment (TEE) such as Trusty. This is typically enabled when the VM is designed to run Android OS, and disabled otherwise.</xs:documentation>
       </xs:annotation>
     </xs:element>
     <xs:element name="hide_mtrr_support" type="Boolean" default="n" minOccurs="0">
diff --git a/misc/config_tools/static_allocators/hv_ram.py b/misc/config_tools/static_allocators/hv_ram.py
index eed41e472..e35c07bc8 100644
--- a/misc/config_tools/static_allocators/hv_ram.py
+++ b/misc/config_tools/static_allocators/hv_ram.py
@@ -17,11 +17,9 @@ def fn(board_etree, scenario_etree, allocation_etree):
     # this dictonary mapped with 'address start':'mem range'
     ram_range = {}
 
-    vm_num = 0
-    vm_list = scenario_etree.xpath("//vm")
-    if vm_list is not None:
-        vm_num = len(vm_list)
-    hv_ram_size = common.HV_BASE_RAM_SIZE + common.VM_RAM_SIZE * vm_num
+    max_vm_num = int(common.get_node(f"//hv/CAPACITIES/MAX_VM_NUM/text()", scenario_etree))
+    max_trusty_vm = len(scenario_etree.xpath(f"//vm[./secure_world_support/text() = 'y']"))
+    hv_ram_size = common.HV_BASE_RAM_SIZE + common.VM_RAM_SIZE * max_vm_num + max_trusty_vm * common.TRUSTY_RAM_SIZE
     ivshmem_list = scenario_etree.xpath("//IVSHMEM_SIZE/text()")
     total_shm_size = 0
     for ram_size in ivshmem_list:
diff --git a/misc/config_tools/xforms/vm_configurations.h.xsl b/misc/config_tools/xforms/vm_configurations.h.xsl
index 98973187a..43bc18ca9 100644
--- a/misc/config_tools/xforms/vm_configurations.h.xsl
+++ b/misc/config_tools/xforms/vm_configurations.h.xsl
@@ -57,6 +57,7 @@
     <xsl:value-of select="acrn:define('PRE_VM_NUM', count(vm[acrn:is-pre-launched-vm(load_order)]), 'U')" />
     <xsl:value-of select="acrn:define('SERVICE_VM_NUM', count(vm[acrn:is-service-vm(load_order)]), 'U')" />
     <xsl:value-of select="acrn:define('MAX_POST_VM_NUM', hv/CAPACITIES/MAX_VM_NUM - count(vm[acrn:is-pre-launched-vm(load_order)]) - count(vm[acrn:is-service-vm(load_order)]) , 'U')" />
+    <xsl:value-of select="acrn:define('MAX_TRUSTY_VM_NUM', count(vm[./secure_world_support/text() = 'y']) , 'U')" />
     <xsl:value-of select="acrn:define('CONFIG_MAX_VM_NUM', hv/CAPACITIES/MAX_VM_NUM , 'U')" />
   </xsl:template>