Re: [PATCH v4 10/12] KVM: selftests: Trigger save+restore randomly in the #PF stress test

[Sean Christopherson <seanjc@google.com>]

On Mon, Jul 27, 2026, Yosry Ahmed wrote:
>  int main(int argc, char *argv[])
>  {
>  	struct kvm_x86_state *state;
>  	int r, i, level;
> +	pthread_t sigusr_thread;
>  	gpa_t gpa, pgtable_gpa;
>  	struct kvm_vcpu *vcpu;
>  	struct kvm_vm *vm;
> @@ -128,18 +156,30 @@ int main(int argc, char *argv[])
>  		pgtable_gpa = PTE_GET_PA(pte);
>  	}
>  
> +	/* Initialize the thread sending SIGUSR and install the handler */
> +	vcpu_sigusr_ignore();
> +	r = pthread_create(&sigusr_thread, NULL, sigusr_thread_fn,
> +			   (void *)pthread_self());
> +	TEST_ASSERT(!r, "pthread_create() failed: %d", r);
> +
>  	for (i = 1; i <= NR_ITERATIONS; i++) {
> +		/*
> +		 * Only handle SIGUSR while the vCPU is running, otherwise
> +		 * ignore it to avoid interrupting other ioctls/syscalls.
> +		 */
> +		vcpu_sigusr_listen();
>  		r = __vcpu_run(vcpu);
> -		TEST_ASSERT(!r, "vcpu_run failed");
> -		TEST_ASSERT_KVM_EXIT_REASON(vcpu, KVM_EXIT_IO);
> -
> -		get_ucall(vcpu, &uc);
> -		if (uc.cmd == UCALL_ABORT) {
> +		if (r == -1)
> +			TEST_ASSERT_EQ(errno, EINTR);

		TEST_ASSERT(!r || errno == EINTR, "Expected success or SIGUSR1");

> +		vcpu_sigusr_ignore();
> +
> +		/* The guest only exits due to a signal or failed assertion */
> +		if (!r) {
> +			TEST_ASSERT_KVM_EXIT_REASON(vcpu, KVM_EXIT_IO);
> +			TEST_ASSERT_EQ(get_ucall(vcpu, &uc), UCALL_ABORT);
>  			REPORT_GUEST_ASSERT(uc);
>  			break;
>  		}
> -		TEST_ASSERT_EQ(uc.cmd, UCALL_SYNC);
> -		TEST_ASSERT_EQ(uc.args[1], i);
>  
>  		state = vcpu_save_state(vcpu);
>  
> @@ -153,8 +193,11 @@ int main(int argc, char *argv[])
>  	pr_info("\n");
>  
>  	sync_global_from_guest(vm, guest_faults);
> +	TEST_ASSERT(guest_faults > 0, "No guest page faults triggered");

Since guest_faults is an unsigned value, the kernel's preferred style is:

	TEST_ASSERT(guest_faults, "No guest page faults triggered");

>  	pr_info("Guest page faults: %lu\n", guest_faults);
>  
> +	pthread_cancel(sigusr_thread);
> +	pthread_join(sigusr_thread, NULL);
>  	kvm_vm_free(vm);
>  	return 0;
>  }
> -- 
> 2.55.0.229.g6434b31f56-goog
>