KVM: selftests: Fix a semaphore imbalance in the dirty ring logging test

[linux-block.git] / tools / testing / selftests / kvm / dirty_log_test.c

diff --git a/tools/testing/selftests/kvm/dirty_log_test.c b/tools/testing/selftests/kvm/dirty_log_test.c
index babea97b31a4307a90de73b86af7ffd93f4b1fbc..eaad5b20854ccf095a4447245554f8ecd48e0506 100644 (file)
--- a/tools/testing/selftests/kvm/dirty_log_test.c
+++ b/tools/testing/selftests/kvm/dirty_log_test.c
@@ -376,7 +376,10 @@ static void dirty_ring_collect_dirty_pages(struct kvm_vcpu *vcpu, int slot,
 
        cleared = kvm_vm_reset_dirty_ring(vcpu->vm);
 
-       /* Cleared pages should be the same as collected */
+       /*
+        * Cleared pages should be the same as collected, as KVM is supposed to
+        * clear only the entries that have been harvested.
+        */
        TEST_ASSERT(cleared == count, "Reset dirty pages (%u) mismatch "
                    "with collected (%u)", cleared, count);
 
@@ -415,12 +418,6 @@ static void dirty_ring_after_vcpu_run(struct kvm_vcpu *vcpu, int ret, int err)
        }
 }
 
-static void dirty_ring_before_vcpu_join(void)
-{
-       /* Kick another round of vcpu just to make sure it will quit */
-       sem_post(&sem_vcpu_cont);
-}
-
 struct log_mode {
        const char *name;
        /* Return true if this mode is supported, otherwise false */
@@ -433,7 +430,6 @@ struct log_mode {
                                     uint32_t *ring_buf_idx);
        /* Hook to call when after each vcpu run */
        void (*after_vcpu_run)(struct kvm_vcpu *vcpu, int ret, int err);
-       void (*before_vcpu_join) (void);
 } log_modes[LOG_MODE_NUM] = {
        {
                .name = "dirty-log",
@@ -452,7 +448,6 @@ struct log_mode {
                .supported = dirty_ring_supported,
                .create_vm_done = dirty_ring_create_vm_done,
                .collect_dirty_pages = dirty_ring_collect_dirty_pages,
-               .before_vcpu_join = dirty_ring_before_vcpu_join,
                .after_vcpu_run = dirty_ring_after_vcpu_run,
        },
 };
@@ -513,14 +508,6 @@ static void log_mode_after_vcpu_run(struct kvm_vcpu *vcpu, int ret, int err)
                mode->after_vcpu_run(vcpu, ret, err);
 }
 
-static void log_mode_before_vcpu_join(void)
-{
-       struct log_mode *mode = &log_modes[host_log_mode];
-
-       if (mode->before_vcpu_join)
-               mode->before_vcpu_join();
-}
-
 static void generate_random_array(uint64_t *guest_array, uint64_t size)
 {
        uint64_t i;
@@ -719,6 +706,7 @@ static void run_test(enum vm_guest_mode mode, void *arg)
        struct kvm_vm *vm;
        unsigned long *bmap;
        uint32_t ring_buf_idx = 0;
+       int sem_val;
 
        if (!log_mode_supported()) {
                print_skip("Log mode '%s' not supported",
@@ -788,12 +776,22 @@ static void run_test(enum vm_guest_mode mode, void *arg)
        /* Start the iterations */
        iteration = 1;
        sync_global_to_guest(vm, iteration);
-       host_quit = false;
+       WRITE_ONCE(host_quit, false);
        host_dirty_count = 0;
        host_clear_count = 0;
        host_track_next_count = 0;
        WRITE_ONCE(dirty_ring_vcpu_ring_full, false);
 
+       /*
+        * Ensure the previous iteration didn't leave a dangling semaphore, i.e.
+        * that the main task and vCPU worker were synchronized and completed
+        * verification of all iterations.
+        */
+       sem_getvalue(&sem_vcpu_stop, &sem_val);
+       TEST_ASSERT_EQ(sem_val, 0);
+       sem_getvalue(&sem_vcpu_cont, &sem_val);
+       TEST_ASSERT_EQ(sem_val, 0);
+
        pthread_create(&vcpu_thread, NULL, vcpu_worker, vcpu);
 
        while (iteration < p->iterations) {
@@ -819,15 +817,21 @@ static void run_test(enum vm_guest_mode mode, void *arg)
                assert(host_log_mode == LOG_MODE_DIRTY_RING ||
                       atomic_read(&vcpu_sync_stop_requested) == false);
                vm_dirty_log_verify(mode, bmap);
-               sem_post(&sem_vcpu_cont);
 
-               iteration++;
+               /*
+                * Set host_quit before sem_vcpu_cont in the final iteration to
+                * ensure that the vCPU worker doesn't resume the guest.  As
+                * above, the dirty ring test may stop and wait even when not
+                * explicitly request to do so, i.e. would hang waiting for a
+                * "continue" if it's allowed to resume the guest.
+                */
+               if (++iteration == p->iterations)
+                       WRITE_ONCE(host_quit, true);
+
+               sem_post(&sem_vcpu_cont);
                sync_global_to_guest(vm, iteration);
        }
 
-       /* Tell the vcpu thread to quit */
-       host_quit = true;
-       log_mode_before_vcpu_join();
        pthread_join(vcpu_thread, NULL);
 
        pr_info("Total bits checked: dirty (%"PRIu64"), clear (%"PRIu64"), "