diff --git a/examples/simple/vmm.c b/examples/simple/vmm.c
index b5ee8d5ba..a037ec2f4 100644
--- a/examples/simple/vmm.c
+++ b/examples/simple/vmm.c
@@ -23,31 +23,35 @@
 // Part of the problem is that we might need multiple DTBs for the same example
 // e.g one DTB for VMM one, one DTB for VMM two. we should be able to hide all
 // of this in the build system to avoid doing any run-time DTB stuff.
+
+/*
+ * As this is just an example, for simplicity we just make the size of the
+ * guest's "RAM" the same for all platforms. For just booting Linux with a
+ * simple user-space, 0x10000000 bytes (256MB) is plenty.
+ */
+#define GUEST_RAM_SIZE 0x10000000
+
 #if defined(BOARD_qemu_arm_virt_hyp)
 #define GUEST_DTB_VADDR 0x4f000000
 #define GUEST_INIT_RAM_DISK_VADDR 0x4d700000
-#define GUEST_RAM_SIZE 0x10000000
 #elif defined(BOARD_rpi4b_hyp)
 #define GUEST_DTB_VADDR 0x2e000000
 #define GUEST_INIT_RAM_DISK_VADDR 0x2d700000
-#define GUEST_RAM_SIZE 0x10000000
 #elif defined(BOARD_odroidc2_hyp)
 #define GUEST_DTB_VADDR 0x2f000000
 #define GUEST_INIT_RAM_DISK_VADDR 0x2d700000
-#define GUEST_RAM_SIZE 0x10000000
 #elif defined(BOARD_odroidc4_hyp)
 #define GUEST_DTB_VADDR 0x2f000000
 #define GUEST_INIT_RAM_DISK_VADDR 0x2d700000
-#define GUEST_RAM_SIZE 0x10000000
 #elif defined(BOARD_imx8mm_evk_hyp)
 #define GUEST_DTB_VADDR 0x4f000000
 #define GUEST_INIT_RAM_DISK_VADDR 0x4d700000
-#define GUEST_RAM_SIZE 0x10000000
 #else
 #error Need to define VM image address and DTB address
 #endif
 
-/* For simplicity we just enforce the serial IRQ channel to be the same across platforms. */
+/* For simplicity we just enforce the serial IRQ channel number to be the same
+ * across platforms. */
 #define SERIAL_IRQ_CH 1
 
 #if defined(BOARD_qemu_arm_virt_hyp)