[PATCH v2 1/2] KVM: selftests: Have perf_test_util signal when to stop vCPUs

Oliver Upton
2022-11-18T21:15:28Z

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>
---
tools/testing/selftests/kvm/access_tracking_perf_test.c | 8 +-------
tools/testing/selftests/kvm/include/perf_test_util.h | 3 +++
tools/testing/selftests/kvm/lib/perf_test_util.c | 3 +++
.../selftests/kvm/memslot_modification_stress_test.c | 6 +-----
4 files changed, 8 insertions(+), 12 deletions(-)

diff --git a/tools/testing/selftests/kvm/access_tracking_perf_test.c b/tools/testing/selftests/kvm/access_tracking_perf_test.c
index 76c583a07ea2..942370d57392 100644
--- 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 eaa88df0555a..536d7c3c3f14 100644
--- 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 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);
}
diff --git a/tools/testing/selftests/kvm/memslot_modification_stress_test.c b/tools/testing/selftests/kvm/memslot_modification_stress_test.c
index bb1d17a1171b..3a5e4518307c 100644
--- 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");

--
2.38.1.584.g0f3c55d4c2-goog