Re: [PATCH net-next v2 04/12] selftests/vsock: avoid multi-VM pidfile collisions with QEMU

On Tue, Nov 04, 2025 at 02:38:54PM -0800, Bobby Eshleman wrote:

From: Bobby Eshleman bobbyeshleman@meta.com

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 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

Changes in v2:

• mention QEMU_OPTS changes in commit message (Simon)

---

tools/testing/selftests/vsock/vmtest.sh | 53 +++++++++++++++++++-------------- 1 file changed, 30 insertions(+), 23 deletions(-)

diff --git a/tools/testing/selftests/vsock/vmtest.sh b/tools/testing/selftests/vsock/vmtest.sh index 03dc4717ac3b..5637c98d5fe8 100755 --- a/tools/testing/selftests/vsock/vmtest.sh +++ b/tools/testing/selftests/vsock/vmtest.sh @@ -23,7 +23,7 @@ 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

# 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 +33,6 @@ 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 \ @@ -89,17 +83,6 @@ vm_ssh() { return $? }

-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

-}

check_args() { local found @@ -188,10 +171,26 @@ handle_build() { popd &>/dev/null }

+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
  

• 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 +200,13 @@ 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 +215,14 @@ 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

} @@ -480,8 +486,6 @@ do done shift $((OPTIND-1))

-trap cleanup EXIT

Why avoiding the cleanup on exit? Should we mention this change in commit description?

Thanks, Stefano

if [[ ${#} -eq 0 ]]; then ARGS=("${TEST_NAMES[@]}") else @@ -496,7 +500,8 @@ handle_build echo "1..${#ARGS[@]}"

log_host "Booting up VM" -vm_start +pidfile="$(mktemp -u $PIDFILE_TEMPLATE)" +vm_start "${pidfile}" vm_wait_for_ssh log_host "VM booted up"

@@ -520,6 +525,8 @@ 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}"

-- 2.47.3