diff --git a/.github/workflows/rust.yml b/.github/workflows/rust.yml
index be9bacd..7334f56 100644
--- a/.github/workflows/rust.yml
+++ b/.github/workflows/rust.yml
@@ -10,6 +10,7 @@ jobs:
   build:
     strategy:
       matrix:
+        mode: [ debug, release ]
         include:
           - arch: riscv64
             qemu-pkg: qemu-system-misc
@@ -36,10 +37,10 @@ jobs:
           components: clippy, rust-src
 
       - name: Run Clippy
-        run: make clippy ARCH=${{ matrix.arch }}
+        run: make clippy ARCH=${{ matrix.arch }} MODE=${{ matrix.mode }}
 
       - name: Test
-        run: make test ARCH=${{ matrix.arch }}
+        run: make test ARCH=${{ matrix.arch }} MODE=${{ matrix.mode }}
 
       - name: Build
-        run: make kernel ARCH=${{ matrix.arch }}
+        run: make kernel ARCH=${{ matrix.arch }} MODE=${{ matrix.mode }}
diff --git a/Makefile b/Makefile
index 5348d1b..db434d8 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,5 @@
 ARCH ?= riscv64
+MODE ?= debug
 
 ifeq ($(ARCH), riscv64)
 	BUILD_TARGET := riscv64imac-unknown-none-elf
@@ -7,6 +8,12 @@ else
 	$(error Invalid TARGET: $(ARCH))
 endif
 
+ifeq ($(MODE), release)
+	CARGO_BUILD_ARGS += --release
+else ifneq ($(MODE), debug)
+	$(error Invalid MODE: $(MODE))
+endif
+
 RUSTFLAGS += -Crelocation-model=static
 RUSTFLAGS += -Ccode-model=medium
 #RUSTFLAGS += -Ctarget-feature=+relax
@@ -19,6 +26,13 @@ CARGO_BUILD_ARGS += -Zbuild-std=core,compiler_builtins,alloc
 CARGO_BUILD_ARGS += -Zbuild-std-features=compiler-builtins-mem
 CARGO_BUILD_ARGS += $(CARGO_TARGET_ARGS)
 
+QEMU = qemu-system-$(ARCH)
+
+QEMU_ARGS  = -nographic -serial mon:stdio -smp 1
+QEMU_ARGS += -machine virt # TODO: override by $(BOARD)
+QEMU_ARGS += -kernel target/$(BUILD_TARGET)/$(MODE)/kernel
+QEMU_ARGS += -initrd build/init.cpio
+
 kernel:
 	env RUSTFLAGS="$(RUSTFLAGS)" cargo build --bin kernel $(CARGO_BUILD_ARGS)
 
@@ -36,7 +50,7 @@ kernel-test-dump:
 	@env RUSTFLAGS="$(RUSTFLAGS)" cargo test $(CARGO_TARGET_ARGS) --bin=kernel --no-run --message-format=json
 
 kernel-asm: kernel
-	riscv64-elf-objdump -d target/$(BUILD_TARGET)/debug/kernel | c++filt -t > kernel.asm
+	riscv64-elf-objdump -d target/$(BUILD_TARGET)/$(MODE)/kernel | c++filt -t > kernel.asm
 
 build-target:
 	@echo $(BUILD_TARGET)
@@ -45,32 +59,9 @@ clean:
 	cargo clean
 
 qemu: kernel
-	qemu-system-$(ARCH) \
-		-nographic -machine virt -serial mon:stdio -smp 1 \
-		-kernel target/$(BUILD_TARGET)/debug/kernel
+	$(QEMU) $(QEMU_ARGS)
 
 qemu-gdb: kernel
-	qemu-system-$(ARCH) \
-		-nographic -machine virt -serial mon:stdio -smp 1 \
-		-kernel target/$(BUILD_TARGET)/debug/kernel \
-		-s -S
+	$(QEMU) $(QEMU_ARGS) -s -S
 
-replay.qcow2:
-	qemu-img create -f qcow2 replay.qcow2 1G
-
-qemu-record: kernel replay.qcow2
-	qemu-system-$(ARCH) \
-		-nographic -machine virt -serial mon:stdio -smp 1 \
-		-kernel target/$(BUILD_TARGET)/debug/kernel \
-		-icount shift=auto,rr=record,rrfile=replay.bin,rrsnapshot=init \
-		-drive file=replay.qcow2,if=none,id=rr
-
-qemu-replay: kernel replay.qcow2
-	qemu-system-$(ARCH) \
-		-nographic -machine virt -serial mon:stdio -smp 1 \
-		-kernel target/$(BUILD_TARGET)/debug/kernel \
-		-icount shift=auto,rr=replay,rrfile=replay.bin,rrsnapshot=init \
-		-drive file=replay.qcow2,if=none,id=rr \
-		-s -S
-
-.PHONY: kernel clippy test kernel-test-dump kernel-asm build-target clean qemu qemu-gdb qemu-record qemu-replay
+.PHONY: kernel clippy test kernel-test-dump kernel-asm build-target clean qemu qemu-gdb