neonvm: makefile targets to introduce cross-compilation of the linux …

…kernel

Signed-off-by: Misha Sakhnov <[email protected]>

Makefile

@@ -12,9 +12,14 @@ GO_BASE_IMG ?= autoscaling-go-base:dev
 E2E_TESTS_VM_IMG ?= vm-postgres:15-bullseye
 PG16_DISK_TEST_IMG ?= pg16-disk-test:dev
 
-## Golang details
+## Golang details (for local tooling)
 GOARCH ?= $(shell go env GOARCH)
 GOOS ?= $(shell go env GOOS)
+
+# The target architecture for linux kernel. Possible values: amd64 or arm64. 
+# Any other supported by linux kernel architecture could be added by introducing new build step into neonvm/hack/kernel/Dockerfile.kernel-builder
+KERNEL_TARGET_ARCH ?= amd64
+
 # Get the currently used golang base path
 GOPATH=$(shell go env GOPATH)
 # Get the currently used golang install path (in GOPATH/bin, unless GOBIN is set)
@@ -244,16 +249,29 @@ ifndef ignore-not-found
   ignore-not-found = false
 endif
 
+# Build the kernel for the amd64 architecture. Uses generic target.
+.PHONY: kernel_amd64
+kernel_amd64: KERNEL_TARGET_ARCH=amd64
+kernel_amd64: kernel
+
+# Build the kernel for the arm64 architecture. Uses generic target.
+.PHONY: kernel_arm64
+kernel_arm64: KERNEL_TARGET_ARCH=arm64
+kernel_arm64: kernel
+
+# Build the kernel for the target architecture.
+# The builder image platform is not specified because the kernel is built for the target architecture using crosscompilation.
+# Target is generic and can be used for any supported architecture by specifying the KERNEL_TARGET_ARCH variable.
 .PHONY: kernel
-kernel: ## Build linux kernel.
+kernel:
 	rm -f neonvm/hack/kernel/vmlinuz; \
 	linux_config=$$(ls neonvm/hack/kernel/linux-config-*) \
 	kernel_version=$${linux_config##*-} \
 	iidfile=$$(mktemp /tmp/iid-XXXXXX); \
 	trap "rm $$iidfile" EXIT; \
 	docker buildx build \
 	    --build-arg KERNEL_VERSION=$$kernel_version \
-		--platform linux/amd64 \
+		--target "kernel_${KERNEL_TARGET_ARCH}" \
 		--pull \
 		--load \
 		--iidfile $$iidfile \

neonvm/hack/kernel/Dockerfile.kernel-builder

@@ -15,6 +15,8 @@ RUN apt-get update && apt-get -y install \
     curl \
     ca-certificates \
     build-essential \
+    gcc-x86-64-linux-gnu \
+    gcc-aarch64-linux-gnu \
     flex \
     bison \
     libelf-dev \
@@ -46,16 +48,31 @@ RUN set -e \
     && tar --strip-components=1 -C linux-${KERNEL_VERSION} -xf linux-${KERNEL_VERSION}.tar.xz
 
 
-FROM build-deps AS build
 
-ARG KERNEL_VERSION
+### Cross-compilation related steps
 
+# Build the kernel on amd64
+FROM build-deps AS build_amd64
+ARG KERNEL_VERSION
 ADD linux-config-${KERNEL_VERSION} linux-${KERNEL_VERSION}/.config
+RUN cd linux-${KERNEL_VERSION} && make ARCH=x86_64 CROSS_COMPILE=x86_64-linux-gnu- -j `nproc`
+
+# Copy the kernel image to a separate step
+# Use alpine so that `cp` is available when loading custom kernels for the runner pod.
+# See the neonvm controller's pod creation logic for more detail.
+FROM alpine:3.19 AS kernel_amd64
+ARG KERNEL_VERSION
+COPY --from=build_amd64 /build/linux-${KERNEL_VERSION}/arch/x86/boot/bzImage /vmlinuz
 
-RUN cd linux-${KERNEL_VERSION} && make -j `nproc`
+# Build the kernel on amd64
+FROM build-deps AS build_arm64
+ARG KERNEL_VERSION
+ADD linux-config-${KERNEL_VERSION} linux-${KERNEL_VERSION}/.config
+RUN cd linux-${KERNEL_VERSION} && make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- -j `nproc`
 
+# Copy the kernel image to a separate step
 # Use alpine so that `cp` is available when loading custom kernels for the runner pod.
 # See the neonvm controller's pod creation logic for more detail.
-FROM alpine:3.19
+FROM alpine:3.19 AS kernel_arm64
 ARG KERNEL_VERSION
-COPY --from=build /build/linux-${KERNEL_VERSION}/arch/x86/boot/bzImage /vmlinuz
+COPY --from=build_arm64 /build/linux-${KERNEL_VERSION}/arch/arm64/boot/Image /vmlinuz