selftests/vsock: avoid multi-VM pidfile collisions with QEMU

Change QEMU to use generated pidfile names instead of just a single
globally-defined pidfile. This allows multiple QEMU instances to
co-exist with different pidfiles. This is required for future tests that
use multiple VMs to check for CID collissions.

Additionally, this also places the burden of killing the QEMU process
and cleaning up the pidfile on the caller of vm_start(). To help with
this, a function terminate_pidfiles() is introduced that callers use to
perform the cleanup. The terminate_pidfiles() function supports multiple
pidfile removals because future patches will need to process two
pidfiles at a time.

Change QEMU_OPTS to be initialized inside the vm_start(). This allows
the generated pidfile to be passed to the string assignment, and
prepares for future vm-specific options as well (e.g., cid).

Signed-off-by: Bobby Eshleman <bobbyeshleman@meta.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Link: https://patch.msgid.link/20251108-vsock-selftests-fixes-and-improvements-v4-4-d5e8d6c87289@meta.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

tools/testing/selftests/vsock/vmtest.sh

@@ -23,7 +23,8 @@ readonly VSOCK_CID=1234
 readonly WAIT_PERIOD=3
 readonly WAIT_PERIOD_MAX=60
 readonly WAIT_TOTAL=$(( WAIT_PERIOD * WAIT_PERIOD_MAX ))
-readonly QEMU_PIDFILE=$(mktemp /tmp/qemu_vsock_vmtest_XXXX.pid)
+readonly PIDFILE_TEMPLATE=/tmp/vsock_vmtest_XXXX.pid
+declare -A PIDFILES
 
 # virtme-ng offers a netdev for ssh when using "--ssh", but we also need a
 # control port forwarded for vsock_test.  Because virtme-ng doesn't support
@@ -33,12 +34,6 @@ readonly QEMU_PIDFILE=$(mktemp /tmp/qemu_vsock_vmtest_XXXX.pid)
 # add the kernel cmdline options that virtme-init uses to setup the interface.
 readonly QEMU_TEST_PORT_FWD="hostfwd=tcp::${TEST_HOST_PORT}-:${TEST_GUEST_PORT}"
 readonly QEMU_SSH_PORT_FWD="hostfwd=tcp::${SSH_HOST_PORT}-:${SSH_GUEST_PORT}"
-readonly QEMU_OPTS="\
-	 -netdev user,id=n0,${QEMU_TEST_PORT_FWD},${QEMU_SSH_PORT_FWD} \
-	 -device virtio-net-pci,netdev=n0 \
-	 -device vhost-vsock-pci,guest-cid=${VSOCK_CID} \
-	 --pidfile ${QEMU_PIDFILE} \
-"
 readonly KERNEL_CMDLINE="\
 	virtme.dhcp net.ifnames=0 biosdevname=0 \
 	virtme.ssh virtme_ssh_channel=tcp virtme_ssh_user=$USER \
@@ -90,15 +85,7 @@ vm_ssh() {
 }
 
 cleanup() {
-	if [[ -s "${QEMU_PIDFILE}" ]]; then
-		pkill -SIGTERM -F "${QEMU_PIDFILE}" > /dev/null 2>&1
-	fi
-
-	# If failure occurred during or before qemu start up, then we need
-	# to clean this up ourselves.
-	if [[ -e "${QEMU_PIDFILE}" ]]; then
-		rm "${QEMU_PIDFILE}"
-	fi
+	terminate_pidfiles "${!PIDFILES[@]}"
 }
 
 check_args() {
@@ -188,10 +175,37 @@ handle_build() {
 	popd &>/dev/null
 }
 
+create_pidfile() {
+	local pidfile
+
+	pidfile=$(mktemp "${PIDFILE_TEMPLATE}")
+	PIDFILES["${pidfile}"]=1
+
+	echo "${pidfile}"
+}
+
+terminate_pidfiles() {
+	local pidfile
+
+	for pidfile in "$@"; do
+		if [[ -s "${pidfile}" ]]; then
+			pkill -SIGTERM -F "${pidfile}" > /dev/null 2>&1
+		fi
+
+		if [[ -e "${pidfile}" ]]; then
+			rm -f "${pidfile}"
+		fi
+
+		unset "PIDFILES[${pidfile}]"
+	done
+}
+
 vm_start() {
+	local pidfile=$1
 	local logfile=/dev/null
 	local verbose_opt=""
 	local kernel_opt=""
+	local qemu_opts=""
 	local qemu
 
 	qemu=$(command -v "${QEMU}")
@@ -201,6 +215,13 @@ vm_start() {
 		logfile=/dev/stdout
 	fi
 
+	qemu_opts="\
+		 -netdev user,id=n0,${QEMU_TEST_PORT_FWD},${QEMU_SSH_PORT_FWD} \
+		 -device virtio-net-pci,netdev=n0 \
+		 -device vhost-vsock-pci,guest-cid=${VSOCK_CID} \
+		--pidfile ${pidfile}
+	"
+
 	if [[ "${BUILD}" -eq 1 ]]; then
 		kernel_opt="${KERNEL_CHECKOUT}"
 	fi
@@ -209,14 +230,14 @@ vm_start() {
 		--run \
 		${kernel_opt} \
 		${verbose_opt} \
-		--qemu-opts="${QEMU_OPTS}" \
+		--qemu-opts="${qemu_opts}" \
 		--qemu="${qemu}" \
 		--user root \
 		--append "${KERNEL_CMDLINE}" \
 		--rw  &> ${logfile} &
 
 	if ! timeout ${WAIT_TOTAL} \
-		bash -c 'while [[ ! -s '"${QEMU_PIDFILE}"' ]]; do sleep 1; done; exit 0'; then
+		bash -c 'while [[ ! -s '"${pidfile}"' ]]; do sleep 1; done; exit 0'; then
 		die "failed to boot VM"
 	fi
 }
@@ -499,7 +520,8 @@ handle_build
 echo "1..${#ARGS[@]}"
 
 log_host "Booting up VM"
-vm_start
+pidfile="$(create_pidfile)"
+vm_start "${pidfile}"
 vm_wait_for_ssh
 log_host "VM booted up"
 
@@ -523,6 +545,8 @@ for arg in "${ARGS[@]}"; do
 	cnt_total=$(( cnt_total + 1 ))
 done
 
+terminate_pidfiles "${pidfile}"
+
 echo "SUMMARY: PASS=${cnt_pass} SKIP=${cnt_skip} FAIL=${cnt_fail}"
 echo "Log: ${LOG}"