KVM: selftests: Track kvm_vcpu object in tsc_scaling_sync

Track the added 'struct kvm_vcpu' object in tsc_scaling_sync instead of
relying purely on the VM + vcpu_id combination.  Ideally, the test
wouldn't need to manually manage vCPUs, but the need to invoke a per-VM
ioctl before creating vCPUs is not handled by the selftests framework,
at least not yet...
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

tools/testing/selftests/kvm/x86_64/tsc_scaling_sync.c

@@ -46,38 +46,41 @@ static void guest_code(void)
 
 static void *run_vcpu(void *_cpu_nr)
 {
-	unsigned long cpu = (unsigned long)_cpu_nr;
+	unsigned long vcpu_id = (unsigned long)_cpu_nr;
 	unsigned long failures = 0;
 	static bool first_cpu_done;
+	struct kvm_vcpu *vcpu;
 
 	/* The kernel is fine, but vm_vcpu_add_default() needs locking */
 	pthread_spin_lock(&create_lock);
 
-	vm_vcpu_add_default(vm, cpu, guest_code);
+	vm_vcpu_add_default(vm, vcpu_id, guest_code);
+	vcpu = vcpu_get(vm, vcpu_id);
 
 	if (!first_cpu_done) {
 		first_cpu_done = true;
-		vcpu_set_msr(vm, cpu, MSR_IA32_TSC, TEST_TSC_OFFSET);
+		vcpu_set_msr(vm, vcpu->id, MSR_IA32_TSC, TEST_TSC_OFFSET);
 	}
 
 	pthread_spin_unlock(&create_lock);
 
 	for (;;) {
-		volatile struct kvm_run *run = vcpu_state(vm, cpu);
+		volatile struct kvm_run *run = vcpu->run;
                 struct ucall uc;
 
-                vcpu_run(vm, cpu);
+		vcpu_run(vm, vcpu->id);
                 TEST_ASSERT(run->exit_reason == KVM_EXIT_IO,
                             "Got exit_reason other than KVM_EXIT_IO: %u (%s)\n",
                             run->exit_reason,
                             exit_reason_str(run->exit_reason));
 
-                switch (get_ucall(vm, cpu, &uc)) {
+		switch (get_ucall(vm, vcpu->id, &uc)) {
                 case UCALL_DONE:
 			goto out;
 
                 case UCALL_SYNC:
-			printf("Guest %ld sync %lx %lx %ld\n", cpu, uc.args[2], uc.args[3], uc.args[2] - uc.args[3]);
+			printf("Guest %d sync %lx %lx %ld\n", vcpu->id,
+			       uc.args[2], uc.args[3], uc.args[2] - uc.args[3]);
 			failures++;
 			break;