KVM: selftests: Verify vCPU migration during IRQ delivery in IRQ test

Extend the eventfd IRQ test with a '-m' flag to have the test migrate the
target vCPU to a random physical CPU before triggering its interrupt, e.g.
to validate KVM's ability to update device posted IRQ routing.

Signed-off-by: David Matlack <dmatlack@google.com>
Co-developed-by: Josh Hilke <jrhilke@google.com>
Signed-off-by: Josh Hilke <jrhilke@google.com>
[sean: pin one vCPU at a time to simplify things, use main()'s affinity]
Link: https://patch.msgid.link/20260626213534.3866178-19-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

1 files changed, 16 insertions, 3 deletions

diff --git a/tools/testing/selftests/kvm/irq_test.c b/tools/testing/selftests/kvm/irq_test.c
index 48520c6dea69..c0ff6e60b167 100644
--- a/tools/testing/selftests/kvm/irq_test.c
+++ b/tools/testing/selftests/kvm/irq_test.c
@@ -157,13 +157,14 @@ static const char *probe_iommu_type(void)
 
 static void help(const char *name)
 {
-	printf("Usage: %s [-a] [-d <segment:bus:device.function>] [-e] [-h] [-i nr_irqs] [-n] [-t iommu_type]\n", name);
+	printf("Usage: %s [-a] [-d <segment:bus:device.function>] [-e] [-h] [-i nr_irqs] [-m] [-n] [-t iommu_type]\n", name);
 	printf("\n");
 	printf("Tests KVM interrupt routing and delivery via irqfd.\n");
 	printf("-a	Affine the device's host IRQ to a random physical CPU\n");
 	printf("-d	Use a VFIO device to send MSI-X interrupts instead of manually signaling the eventfd\n");
 	printf("-e	Set empty GSI routing in-between some interrupts\n");
 	printf("-i	The number of IRQs to generate during the test\n");
+	printf("-m	Pin target vCPU to random physical CPU before triggering interrupt\n");
 	printf("-n	Deliver 50 percent of IRQs as non-maskable interrupts\n");
 	printf("-t	Override the IOMMU type to use (vfio_type1_iommu or iommufd)\n");
 	printf("\n");
@@ -195,12 +196,14 @@ int main(int argc, char **argv)
 	const char *device_bdf = NULL;
 	const char *iommu_type = NULL;
 	int i, j, c, msix, eventfd;
+	bool migrate_vcpus = false;
+	cpu_set_t available_cpus;
 	bool use_nmi = false;
 	struct iommu *iommu;
 	struct kvm_vm *vm;
 	int irq, irq_cpu;
 
-	while ((c = getopt(argc, argv, "ad:ehi:nt:")) != -1) {
+	while ((c = getopt(argc, argv, "ad:ehi:mnt:")) != -1) {
 		switch (c) {
 		case 'a':
 			irq_affinity = true;
@@ -214,6 +217,9 @@ int main(int argc, char **argv)
 		case 'i':
 			nr_irqs = atoi_positive("Number of IRQs", optarg);
 			break;
+		case 'm':
+			migrate_vcpus = true;
+			break;
 		case 'n':
 			use_nmi = true;
 			break;
@@ -248,7 +254,6 @@ int main(int argc, char **argv)
 
 		eventfd = kvm_new_eventfd();
 		irq = -1;
-		irq_cpu = -1;
 	}
 
 	pr_info("Injecting interrupts for GSI %d (guest vector 0x%x) %d times\n",
@@ -256,6 +261,9 @@ int main(int argc, char **argv)
 
 	kvm_assign_irqfd(vm, gsi, eventfd);
 
+	if (migrate_vcpus)
+		kvm_sched_getaffinity(0, sizeof(available_cpus), &available_cpus);
+
 	for (i = 0; i < nr_vcpus; i++)
 		pthread_create(&vcpu_threads[i], NULL, vcpu_thread_main, vcpus[i]);
 
@@ -266,6 +274,8 @@ int main(int argc, char **argv)
 			continue;
 	}
 
+	irq_cpu = -1;
+
 	for (i = 0; i < nr_irqs; i++) {
 		const bool do_set_empty_routing = set_empty_routing && (i & BIT(3));
 		const bool do_use_nmi = use_nmi && (i & BIT(2));
@@ -282,6 +292,9 @@ int main(int argc, char **argv)
 			proc_irq_set_smp_affinity(irq, irq_cpu);
 		}
 
+		if (migrate_vcpus)
+			pin_task_to_random_cpu(vcpu_threads[i % nr_vcpus], &available_cpus);
+
 		for (j = 0; j < nr_vcpus; j++) {
 			TEST_ASSERT(!GUEST_RECEIVED_IRQ(vcpus[j]),
 				    "IRQ flag for vCPU %d not clear prior to test",