KVM: selftests: Have perf_test_util signal when to stop vCPUs

Signal that a test run is complete through perf_test_args instead of
having tests open code a similar solution. Ensure that the field resets
to false at the beginning of a test run as the structure is reused
between test runs, eliminating a couple of bugs:

access_tracking_perf_test hangs indefinitely on a subsequent test run,
as 'done' remains true. The bug doesn't amount to much right now, as x86
supports a single guest mode. However, this is a precondition of
enabling the test for other architectures with >1 guest mode, like
arm64.

memslot_modification_stress_test has the exact opposite problem, where
subsequent test runs complete immediately as 'run_vcpus' remains false.

Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
[oliver: added commit message, preserve spin_wait_for_next_iteration()]
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20221118211503.4049023-2-oliver.upton@linux.dev

1 files changed, 3 insertions, 0 deletions

diff --git a/tools/testing/selftests/kvm/lib/perf_test_util.c b/tools/testing/selftests/kvm/lib/perf_test_util.c
index 9618b37c66f7..ee3f499ccbd2 100644
--- a/tools/testing/selftests/kvm/lib/perf_test_util.c
+++ b/tools/testing/selftests/kvm/lib/perf_test_util.c
@@ -267,6 +267,7 @@ void perf_test_start_vcpu_threads(int nr_vcpus,
 
 	vcpu_thread_fn = vcpu_fn;
 	WRITE_ONCE(all_vcpu_threads_running, false);
+	WRITE_ONCE(perf_test_args.stop_vcpus, false);
 
 	for (i = 0; i < nr_vcpus; i++) {
 		struct vcpu_thread *vcpu = &vcpu_threads[i];
@@ -289,6 +290,8 @@ void perf_test_join_vcpu_threads(int nr_vcpus)
 {
 	int i;
 
+	WRITE_ONCE(perf_test_args.stop_vcpus, true);
+
 	for (i = 0; i < nr_vcpus; i++)
 		pthread_join(vcpu_threads[i].thread, NULL);
 }