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

diff --git a/tools/testing/selftests/kvm/access_tracking_perf_test.c b/tools/testing/selftests/kvm/access_tracking_perf_test.c
index 76c583a..942370d 100644 (file)
--- a/tools/testing/selftests/kvm/access_tracking_perf_test.c
+++ b/tools/testing/selftests/kvm/access_tracking_perf_test.c
@@ -58,9 +58,6 @@ static enum {
        ITERATION_MARK_IDLE,
 } iteration_work;
 
-/* Set to true when vCPU threads should exit. */
-static bool done;
-
 /* The iteration that was last completed by each vCPU. */
 static int vcpu_last_completed_iteration[KVM_MAX_VCPUS];
 
@@ -211,7 +208,7 @@ static bool spin_wait_for_next_iteration(int *current_iteration)
        int last_iteration = *current_iteration;
 
        do {
-               if (READ_ONCE(done))
+               if (READ_ONCE(perf_test_args.stop_vcpus))
                        return false;
 
                *current_iteration = READ_ONCE(iteration);
@@ -321,9 +318,6 @@ static void run_test(enum vm_guest_mode mode, void *arg)
        mark_memory_idle(vm, nr_vcpus);
        access_memory(vm, nr_vcpus, ACCESS_READ, "Reading from idle memory");
 
-       /* Set done to signal the vCPU threads to exit */
-       done = true;
-
        perf_test_join_vcpu_threads(nr_vcpus);
        perf_test_destroy_vm(vm);
 }

diff --git a/tools/testing/selftests/kvm/include/perf_test_util.h b/tools/testing/selftests/kvm/include/perf_test_util.h
index eaa88df..536d7c3 100644 (file)
--- a/tools/testing/selftests/kvm/include/perf_test_util.h
+++ b/tools/testing/selftests/kvm/include/perf_test_util.h
@@ -40,6 +40,9 @@ struct perf_test_args {
        /* Run vCPUs in L2 instead of L1, if the architecture supports it. */
        bool nested;
 
+       /* Test is done, stop running vCPUs. */
+       bool stop_vcpus;
+
        struct perf_test_vcpu_args vcpu_args[KVM_MAX_VCPUS];
 };
 

diff --git a/tools/testing/selftests/kvm/lib/perf_test_util.c b/tools/testing/selftests/kvm/lib/perf_test_util.c
index 9618b37..ee3f499 100644 (file)
--- 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);
 }

diff --git a/tools/testing/selftests/kvm/memslot_modification_stress_test.c b/tools/testing/selftests/kvm/memslot_modification_stress_test.c
index bb1d17a..3a5e451 100644 (file)
--- a/tools/testing/selftests/kvm/memslot_modification_stress_test.c
+++ b/tools/testing/selftests/kvm/memslot_modification_stress_test.c
@@ -34,8 +34,6 @@
 static int nr_vcpus = 1;
 static uint64_t guest_percpu_mem_size = DEFAULT_PER_VCPU_MEM_SIZE;
 
-static bool run_vcpus = true;
-
 static void vcpu_worker(struct perf_test_vcpu_args *vcpu_args)
 {
        struct kvm_vcpu *vcpu = vcpu_args->vcpu;
@@ -45,7 +43,7 @@ static void vcpu_worker(struct perf_test_vcpu_args *vcpu_args)
        run = vcpu->run;
 
        /* Let the guest access its memory until a stop signal is received */
-       while (READ_ONCE(run_vcpus)) {
+       while (!READ_ONCE(perf_test_args.stop_vcpus)) {
                ret = _vcpu_run(vcpu);
                TEST_ASSERT(ret == 0, "vcpu_run failed: %d\n", ret);
 
@@ -110,8 +108,6 @@ static void run_test(enum vm_guest_mode mode, void *arg)
        add_remove_memslot(vm, p->memslot_modification_delay,
                           p->nr_memslot_modifications);
 
-       run_vcpus = false;
-
        perf_test_join_vcpu_threads(nr_vcpus);
        pr_info("All vCPU threads joined\n");