From c235cb62beefd03087e7cfc7f7f55f0c7c6601c9 Mon Sep 17 00:00:00 2001
From: Lena <lena@omega>
Date: Sat, 1 Aug 2026 00:00:00 +0000
Subject: Enter vmm

A QEMU/KVM virtual machine manager in one POSIX shell script. Each
VM is a directory of plain files under $VMMDIR, configured by a
hand-edited KEY=VALUE file that is parsed rather than sourced, so
nothing in it can inject a raw QEMU argument.

Control is a QMP FIFO pair inside that directory, guarded by its
permissions alone; nothing binds a TCP port. The tests are TAP
without a framework and boot real guests where the host allows.
---
 tests/lock | 51 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 51 insertions(+)
 create mode 100644 tests/lock

(limited to 'tests/lock')

diff --git a/tests/lock b/tests/lock
new file mode 100644
index 0000000..09c357f
--- /dev/null
+++ b/tests/lock
@@ -0,0 +1,51 @@
+# The VM directory is the mutex.
+
+"$VMM" create lk1 64M >/dev/null 2>&1
+
+# Every mutating verb serialises, including the two that destroy data.
+exec 9<"$VMMDIR/lk1"
+flock -n 9
+exits 4 "start refuses while the lock is held" start lk1
+exits 4 "delete refuses while the lock is held" delete -f lk1
+exits 4 "clone refuses while the lock is held" clone lk1 lk9
+flock -u 9
+exec 9>&-
+
+# The kernel releases the lock when vmm exits on an error.
+cfg lk1 <<EOF
+NOSUCHKEY=1
+EOF
+refuses 'unknown key' "start refuses a broken config" start lk1
+exits 0 "and gives back the lock it had already taken" stop lk1
+
+# Two real vmm processes, not a directory made by hand. A guest with no
+# OS ignores ACPI, so stop holds the lock for SHUTDOWN_TIMEOUT, which is
+# long enough to fire a start at it and require a refusal.
+"$VMM" create lk2 64M >/dev/null 2>&1
+cfg lk2 <<EOF
+MEM=256
+CPUS=1
+HWACCEL=no
+EOF
+if "$VMM" start lk2 >/dev/null 2>&1; then
+	"$VMM" stop lk2 >/dev/null 2>&1 &
+	stopper=$!
+	i=0
+	while flock -n "$VMMDIR/lk2" true && [ "$i" -lt 5 ]; do
+		sleep 1
+		i=$((i + 1))
+	done
+	# That loop ends on the lock being taken or on running out of
+	# patience, and only the first of those says anything about vmm.
+	if flock -n "$VMMDIR/lk2" true; then
+		skip 1 "the backgrounded stop never took the lock"
+	else
+		exits 4 "a second vmm is refused while the first holds the lock" \
+			start lk2
+	fi
+	wait "$stopper" 2>/dev/null || :
+	holds "and the lock is available once the first is done" \
+		flock -n "$VMMDIR/lk2" true
+else
+	skip 2 "lk2 did not start"
+fi
-- 
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