diff --git a/arch/src/aarch64/layout.rs b/arch/src/aarch64/layout.rs
index da029cbda..02792b7fc 100644
--- a/arch/src/aarch64/layout.rs
+++ b/arch/src/aarch64/layout.rs
@@ -46,10 +46,11 @@
 
 use vm_memory::GuestAddress;
 
-/// 0x0 ~ 0x400_0000 is reserved to uefi
+/// 0x0 ~ 0x40_0000 (4 MiB) is reserved to UEFI
+/// UEFI binary size is required less than 3 MiB, reserving 4 MiB is enough.
 pub const UEFI_START: u64 = 0x0;
 pub const MEM_UEFI_START: GuestAddress = GuestAddress(0);
-pub const UEFI_SIZE: u64 = 0x0400_0000;
+pub const UEFI_SIZE: u64 = 0x040_0000;
 
 /// Below this address will reside the GIC, above this address will reside the MMIO devices.
 pub const MAPPED_IO_START: u64 = 0x0900_0000;
diff --git a/arch/src/aarch64/mod.rs b/arch/src/aarch64/mod.rs
index 01fe78ced..52a326194 100644
--- a/arch/src/aarch64/mod.rs
+++ b/arch/src/aarch64/mod.rs
@@ -88,7 +88,7 @@ pub fn configure_vcpu(
 pub fn arch_memory_regions(size: GuestUsize) -> Vec<(GuestAddress, usize, RegionType)> {
     // Normally UEFI should be loaded to a flash area at the beginning of memory.
     // But now flash memory type is not supported.
-    // As a workaround, we take 64 MiB memory from the main RAM for UEFI.
+    // As a workaround, we take 4 MiB memory from the main RAM for UEFI.
     // As a result, the RAM that the guest can see is less than what has been
     // assigned in command line, when ACPI and UEFI is enabled.
     let ram_deduction = if cfg!(feature = "acpi") {
@@ -98,7 +98,7 @@ pub fn arch_memory_regions(size: GuestUsize) -> Vec<(GuestAddress, usize, Region
     };
 
     vec![
-        // 0 ~ 64 MiB: Reserved for UEFI space
+        // 0 ~ 4 MiB: Reserved for UEFI space
         #[cfg(feature = "acpi")]
         (GuestAddress(0), layout::UEFI_SIZE as usize, RegionType::Ram),
         #[cfg(not(feature = "acpi"))]
@@ -107,7 +107,7 @@ pub fn arch_memory_regions(size: GuestUsize) -> Vec<(GuestAddress, usize, Region
             layout::UEFI_SIZE as usize,
             RegionType::Reserved,
         ),
-        // 64 MiB ~ 256 MiB: Gic and legacy devices
+        // 4 MiB ~ 256 MiB: Gic and legacy devices
         (
             GuestAddress(layout::UEFI_SIZE),
             (layout::MEM_32BIT_DEVICES_START.0 - layout::UEFI_SIZE) as usize,