Re: [PATCH v5 07/21] KVM: selftests: Verify IRQ bypass works in IRQ test

[Sean Christopherson <seanjc@google.com>]

On Thu, Jun 04, 2026, Josh Hilke wrote:
> @@ -76,9 +109,10 @@ static void kvm_route_msi(struct kvm_vm *vm, u32 gsi, struct kvm_vcpu *vcpu,
>  
>  static void help(const char *name)
>  {
> -	printf("Usage: %s [-h]\n", name);
> +	printf("Usage: %s [-d <segment:bus:device.function>] [-h]\n", name);
>  	printf("\n");
>  	printf("Tests KVM IRQ injection via irqfd using an emulated eventfd.\n");
> +	printf("-d	Use a VFIO device to send MSI-X interrupts instead of using an emulated eventfd\n");


	printf("-d	Use a VFIO device to send MSI-X interrupts instead of manually signaling the eventfd\n");

>  	printf("\n");
>  	exit(KSFT_FAIL);
>  }
> @@ -100,14 +134,21 @@ int main(int argc, char **argv)
>  	u32 gsi = kvm_random_u64_in_range(&kvm_rng, 24, KVM_MAX_IRQ_ROUTES - 1);
>  	u8 vector = kvm_random_u64_in_range(&kvm_rng, 32, UINT8_MAX);
>  
> -	struct kvm_vcpu *vcpus[KVM_MAX_VCPUS];
>  	pthread_t vcpu_threads[KVM_MAX_VCPUS];
> +	struct kvm_vcpu *vcpus[KVM_MAX_VCPUS];
> +	struct vfio_pci_device *device = NULL;
>  	int nr_irqs = 1000, nr_vcpus = 1;
> -	int i, j, c, eventfd;
> +	const char *device_bdf = NULL;
> +	int i, j, c, msix, eventfd;
> +	struct iommu *iommu;
>  	struct kvm_vm *vm;
> +	unsigned int irq;

I think it makes sense to track "irq" as a signed int, so that the !device path
can set it to -1.  Then it can be printed somewhat blindly without being outright
wrong.

> -	while ((c = getopt(argc, argv, "h")) != -1) {
> +	while ((c = getopt(argc, argv, "d:h")) != -1) {
>  		switch (c) {
> +		case 'd':
> +			device_bdf = optarg;
> +			break;
>  		case 'h':
>  		default:
>  			help(argv[0]);
> @@ -119,7 +160,17 @@ int main(int argc, char **argv)
>  	vm = vm_create_with_vcpus(nr_vcpus, guest_code, vcpus);
>  	vm_install_exception_handler(vm, vector, guest_irq_handler);
>  
> -	eventfd = kvm_new_eventfd();
> +	if (device_bdf) {
> +		iommu = iommu_init(default_iommu_mode);
> +		device = vfio_pci_device_init(device_bdf, iommu);
> +		msix = vfio_setup_msi(device);
> +		irq = vfio_msix_to_host_irq(device_bdf, msix);
> +		eventfd = device->msi_eventfds[msix];
> +		printf("Using device %s MSI-X[%d] (IRQ-%u)\n", device_bdf, msix,
> +		       irq);
> +	} else {
> +		eventfd = kvm_new_eventfd();
> +	}
>  
>  	printf("Injecting interrupts for GSI %d (Vector 0x%x) %d times\n",
>  	       gsi, vector, nr_irqs);
> @@ -147,8 +198,7 @@ int main(int argc, char **argv)
>  				    "IRQ flag for vCPU %d not clear prior to test",
>  				    vcpus[j]->id);

Print the IRQ in the assert.  Ditto for the pCPU in the future.  Providing more
debug information is nice, but it should *always* be secondary to providing info
in the assert/error itself.

		TEST_ASSERT(GUEST_RECEIVED_INTERRUPT(vcpu, do_use_nmi),
			    "vCPU %d timed out waiting for %s (vector 0x%x) from GSI %d (via CPU %d)\n",
			    vcpu->id, do_use_nmi ? "NMI" : "IRQ",
			    do_use_nmi ? NMI_VECTOR : vector, gsi, irq_cpu);


>  
> -		/* Trigger interrupt */
> -		eventfd_write(eventfd, 1);
> +		trigger_interrupt(device, eventfd);
>  
>  		clock_gettime(CLOCK_MONOTONIC, &start);
>  		for (;;) {
> -- 
> 2.54.0.1032.g2f8565e1d1-goog
>