[PATCH kvm-unit-tests v2 4/6] s390x: smp: Create and use a non-waiting CPU stop

[Eric Farman <farman@linux.ibm.com>]

When stopping a CPU, kvm-unit-tests serializes/waits for everything
to finish, in order to get a consistent result whenever those
functions are used.

But to test the SIGP STOP itself, these additional measures could
mask other problems. For example, did the STOP work, or is the CPU
still operating?

Let's create a non-waiting SIGP STOP and use it here, to ensure that
the CPU is correctly stopped. A smp_cpu_stopped() call will still
be used to see that the SIGP STOP has been processed, and the state
of the CPU can be used to determine whether the test passes/fails.

Signed-off-by: Eric Farman <farman@linux.ibm.com>
Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
---
 lib/s390x/smp.c | 27 +++++++++++++++++++++++++++
 lib/s390x/smp.h |  1 +
 s390x/smp.c     | 17 +++++++++--------
 3 files changed, 37 insertions(+), 8 deletions(-)

diff --git a/lib/s390x/smp.c b/lib/s390x/smp.c
index 368d6add..b69c0e09 100644
--- a/lib/s390x/smp.c
+++ b/lib/s390x/smp.c
@@ -119,6 +119,33 @@ int smp_cpu_stop(uint16_t idx)
 	return rc;
 }
 
+/*
+ * Functionally equivalent to smp_cpu_stop(), but without the
+ * elements that wait/serialize matters itself.
+ * Used to see if KVM itself is serialized correctly.
+ */
+int smp_cpu_stop_nowait(uint16_t idx)
+{
+	check_idx(idx);
+
+	/* refuse to work on the boot CPU */
+	if (idx == 0)
+		return -1;
+
+	spin_lock(&lock);
+
+	/* Don't suppress a CC2 with sigp_retry() */
+	if (sigp(cpus[idx].addr, SIGP_STOP, 0, NULL)) {
+		spin_unlock(&lock);
+		return -1;
+	}
+
+	cpus[idx].active = false;
+	spin_unlock(&lock);
+
+	return 0;
+}
+
 int smp_cpu_stop_store_status(uint16_t idx)
 {
 	int rc;
diff --git a/lib/s390x/smp.h b/lib/s390x/smp.h
index 1e69a7de..bae03dfd 100644
--- a/lib/s390x/smp.h
+++ b/lib/s390x/smp.h
@@ -44,6 +44,7 @@ bool smp_sense_running_status(uint16_t idx);
 int smp_cpu_restart(uint16_t idx);
 int smp_cpu_start(uint16_t idx, struct psw psw);
 int smp_cpu_stop(uint16_t idx);
+int smp_cpu_stop_nowait(uint16_t idx);
 int smp_cpu_stop_store_status(uint16_t idx);
 int smp_cpu_destroy(uint16_t idx);
 int smp_cpu_setup(uint16_t idx, struct psw psw);
diff --git a/s390x/smp.c b/s390x/smp.c
index 50811bd0..f70a9c54 100644
--- a/s390x/smp.c
+++ b/s390x/smp.c
@@ -76,14 +76,15 @@ static void test_restart(void)
 
 static void test_stop(void)
 {
-	smp_cpu_stop(1);
-	/*
-	 * The smp library waits for the CPU to shut down, but let's
-	 * also do it here, so we don't rely on the library
-	 * implementation
-	 */
-	while (!smp_cpu_stopped(1)) {}
-	report_pass("stop");
+	int rc;
+
+	report_prefix_push("stop");
+
+	rc = smp_cpu_stop_nowait(1);
+	report(!rc, "return code");
+	report(smp_cpu_stopped(1), "cpu stopped");
+
+	report_prefix_pop();
 }
 
 static void test_stop_store_status(void)
-- 
2.32.0