diff --git a/target/product/aosp_arm.mk b/target/product/aosp_arm.mk
index 8c8f407..a052b3a 100644
--- a/target/product/aosp_arm.mk
+++ b/target/product/aosp_arm.mk
@@ -14,6 +14,13 @@
 # limitations under the License.
 #
 
+# The system image of aosp_arm-userdebug is a GSI for the devices with:
+# - ARM 32 bits user space
+# - 64 bits binder interface
+# - system-as-root
+# - VNDK enforcement
+# - compatible property override enabled
+
 PRODUCT_PROPERTY_OVERRIDES += \
 	rild.libpath=/vendor/lib/libreference-ril.so
 
@@ -27,6 +34,13 @@
 
 include $(SRC_TARGET_DIR)/product/full.mk
 
+# Enable A/B update
+AB_OTA_UPDATER := true
+AB_OTA_PARTITIONS := system
+PRODUCT_PACKAGES += \
+    update_engine \
+    update_verifier
+
 # Needed by Pi newly launched device to pass VtsTrebleSysProp on GSI
 PRODUCT_COMPATIBLE_PROPERTY_OVERRIDE := true
 
diff --git a/target/product/aosp_arm64.mk b/target/product/aosp_arm64.mk
index aeff3f0..efbc300 100644
--- a/target/product/aosp_arm64.mk
+++ b/target/product/aosp_arm64.mk
@@ -14,6 +14,13 @@
 # limitations under the License.
 #
 
+# The system image of aosp_arm64-userdebug is a GSI for the devices with:
+# - ARM 64 bits user space
+# - 64 bits binder interface
+# - system-as-root
+# - VNDK enforcement
+# - compatible property override enabled
+
 PRODUCT_PROPERTY_OVERRIDES += \
 	rild.libpath=/vendor/lib64/libreference-ril.so
 
@@ -44,6 +51,13 @@
 
 include $(SRC_TARGET_DIR)/product/emulator.mk
 
+# Enable A/B update
+AB_OTA_UPDATER := true
+AB_OTA_PARTITIONS := system
+PRODUCT_PACKAGES += \
+    update_engine \
+    update_verifier
+
 # Needed by Pi newly launched device to pass VtsTrebleSysProp on GSI
 PRODUCT_COMPATIBLE_PROPERTY_OVERRIDE := true
 
diff --git a/target/product/aosp_arm64_ab.mk b/target/product/aosp_arm64_ab.mk
index c96cb91..d389c74 100644
--- a/target/product/aosp_arm64_ab.mk
+++ b/target/product/aosp_arm64_ab.mk
@@ -19,8 +19,14 @@
 # on the generic system image, place them in build/make/target/board/
 # treble_system.prop.
 
+# aosp_arm64_ab-userdebug is a Legacy GSI for the devices with:
+# - ARM 64 bits user space
+# - 64 bits binder interface
+# - system-as-root
+
 include build/make/target/product/treble_common_64.mk
 
+# Enable A/B update
 AB_OTA_UPDATER := true
 AB_OTA_PARTITIONS := system
 PRODUCT_PACKAGES += \
diff --git a/target/product/aosp_arm_ab.mk b/target/product/aosp_arm_ab.mk
index 98b2f99..5845d3b 100644
--- a/target/product/aosp_arm_ab.mk
+++ b/target/product/aosp_arm_ab.mk
@@ -19,8 +19,14 @@
 # on the generic system image, place them in build/make/target/board/
 # treble_system.prop.
 
+# aosp_arm_ab-userdebug is a Legacy GSI for the devices with:
+# - ARM 32 bits user space
+# - 32 bits binder interface
+# - system-as-root
+
 include build/make/target/product/treble_common_32.mk
 
+# Enable A/B update
 AB_OTA_UPDATER := true
 AB_OTA_PARTITIONS := system
 PRODUCT_PACKAGES += \
diff --git a/target/product/aosp_x86.mk b/target/product/aosp_x86.mk
index b044149..7929a3e 100644
--- a/target/product/aosp_x86.mk
+++ b/target/product/aosp_x86.mk
@@ -14,6 +14,13 @@
 # limitations under the License.
 #
 
+# The system image of aosp_x86-userdebug is a GSI for the devices with:
+# - x86 32 bits user space
+# - 64 bits binder interface
+# - system-as-root
+# - VNDK enforcement
+# - compatible property override enabled
+
 PRODUCT_PROPERTY_OVERRIDES += \
 	rild.libpath=/vendor/lib/libreference-ril.so
 
@@ -28,6 +35,13 @@
 
 include $(SRC_TARGET_DIR)/product/full_x86.mk
 
+# Enable A/B update
+AB_OTA_UPDATER := true
+AB_OTA_PARTITIONS := system
+PRODUCT_PACKAGES += \
+    update_engine \
+    update_verifier
+
 # Needed by Pi newly launched device to pass VtsTrebleSysProp on GSI
 PRODUCT_COMPATIBLE_PROPERTY_OVERRIDE := true
 
diff --git a/target/product/aosp_x86_64.mk b/target/product/aosp_x86_64.mk
index 4d2589e..5a934a9 100644
--- a/target/product/aosp_x86_64.mk
+++ b/target/product/aosp_x86_64.mk
@@ -14,6 +14,13 @@
 # limitations under the License.
 #
 
+# The system image of aosp_x86_64-userdebug is a GSI for the devices with:
+# - x86 64 bits user space
+# - 64 bits binder interface
+# - system-as-root
+# - VNDK enforcement
+# - compatible property override enabled
+
 PRODUCT_PROPERTY_OVERRIDES += \
 	rild.libpath=/vendor/lib64/libreference-ril.so
 
@@ -41,6 +48,13 @@
 
 include $(SRC_TARGET_DIR)/product/emulator.mk
 
+# Enable A/B update
+AB_OTA_UPDATER := true
+AB_OTA_PARTITIONS := system
+PRODUCT_PACKAGES += \
+    update_engine \
+    update_verifier
+
 # Needed by Pi newly launched device to pass VtsTrebleSysProp on GSI
 PRODUCT_COMPATIBLE_PROPERTY_OVERRIDE := true
 
diff --git a/target/product/aosp_x86_64_ab.mk b/target/product/aosp_x86_64_ab.mk
index 4590dc5..d9163d7 100644
--- a/target/product/aosp_x86_64_ab.mk
+++ b/target/product/aosp_x86_64_ab.mk
@@ -19,8 +19,14 @@
 # on the generic system image, place them in build/make/target/board/
 # treble_system.prop.
 
+# aosp_x86_64_ab-userdebug is a Legacy GSI for the devices with:
+# - x86 64 bits user space
+# - 64 bits binder interface
+# - system-as-root
+
 include build/make/target/product/treble_common_64.mk
 
+# Enable A/B update
 AB_OTA_UPDATER := true
 AB_OTA_PARTITIONS := system
 PRODUCT_PACKAGES += \
diff --git a/target/product/aosp_x86_ab.mk b/target/product/aosp_x86_ab.mk
index 404a4da..4fff3d1 100644
--- a/target/product/aosp_x86_ab.mk
+++ b/target/product/aosp_x86_ab.mk
@@ -19,8 +19,14 @@
 # on the generic system image, place them in build/make/target/board/
 # treble_system.prop.
 
+# aosp_x86_ab-userdebug is a Legacy GSI for the devices with:
+# - x86 32 bits user space
+# - 32 bits binder interface
+# - system-as-root
+
 include build/make/target/product/treble_common_32.mk
 
+# Enable A/B update
 AB_OTA_UPDATER := true
 AB_OTA_PARTITIONS := system
 PRODUCT_PACKAGES += \