kernel: add arm experimental kernel build support

Add a new entry of arm-kernel-experimental and let the kernel build
script support to build it.

Fixes: #3280
Signed-off-by: Jianyong Wu <jianyong.wu@arm.com>

tools/packaging/kernel/build-kernel.sh

@@ -89,6 +89,7 @@ Options:
 	-c <path>   	: Path to config file to build the kernel.
 	-d          	: Enable bash debug.
 	-e          	: Enable experimental kernel.
+	-E          	: Enable arch-specific experimental kernel, arch info offered by "-a".
 	-f          	: Enable force generate config when setup.
 	-g <vendor> 	: GPU vendor, intel or nvidia.
 	-h          	: Display this help.
@@ -462,7 +463,7 @@ install_kata() {
 }
 
 main() {
-	while getopts "a:b:c:defg:hk:p:st:v:x:" opt; do
+	while getopts "a:b:c:deEfg:hk:p:t:v:x:" opt; do	
 		case "$opt" in
 			a)
 				arch_target="${OPTARG}"
@@ -480,6 +481,9 @@ main() {
 			e)
 				build_type="experimental"
 				;;
+			E)
+				build_type="arch-experimental"
+				;;
 			f)
 				force_setup_generate_config="true"
 				;;
@@ -525,6 +529,17 @@ main() {
 	if [ -z "$kernel_version" ]; then
 		if [[ ${build_type} == "experimental" ]]; then
 			kernel_version=$(get_from_kata_deps "assets.kernel-experimental.tag")
+		elif [[ ${build_type} == "arch-experimental" ]]; then
+			case "${arch_target}" in
+			"aarch64")
+				build_type="arm-experimental"
+				kernel_version=$(get_from_kata_deps "assets.arm-kernel-experimental.version")
+			;;
+			*)
+				info "No arch-specific experimental kernel supported, using experimental one instead"
+				kernel_version=$(get_from_kata_deps "assets.kernel-experimental.tag")
+			;;
+			esac
 		elif [[ "${conf_guest}" == "tdx" ]]; then
 			 kernel_version=$(get_from_kata_deps "assets.kernel.tdx.tag")
 		else

versions.yaml

@@ -164,6 +164,11 @@ assets:
     url: "https://cdn.kernel.org/pub/linux/kernel/v5.x/"
     tag: "v5.13.10"
 
+  arm-kernel-experimental:
+    description: "Linux kernel with cpu/mem hotplug support on arm64"
+    url: "https://cdn.kernel.org/pub/linux/kernel/v5.x/"
+    version: "v5.15.7"
+
 externals:
   description: "Third-party projects used by the system"