[PATCH v8 12/20] KVM: selftests: Add option to set empty routing between IRQs in eventfd IRQ test

[Sean Christopherson <seanjc@google.com>]

From: David Matlack <dmatlack@google.com>

Extend the eventfd IRQ test with an '-e' flag to set empty GSI routing
between interrupts.  Clobbering the GSI routing table verifies that KVM
correctly handles CPUx => NULL => CPUy transitions, not just CPUx => CPUy
transitions, and verifies that KVM can "rebuild" an entire routing setup.

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: '-e' for "empty" instead of '-c' for "clear", massage changelog]
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 tools/testing/selftests/kvm/irq_test.c | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/kvm/irq_test.c b/tools/testing/selftests/kvm/irq_test.c
index fd386e3e9ac3..fd03ec940362 100644
--- a/tools/testing/selftests/kvm/irq_test.c
+++ b/tools/testing/selftests/kvm/irq_test.c
@@ -121,6 +121,13 @@ static void kvm_route_msi(struct kvm_vm *vm, u32 gsi, struct kvm_vcpu *vcpu,
 	vm_ioctl(vm, KVM_SET_GSI_ROUTING, &routing.header);
 }
 
+static void kvm_set_empty_gsi_routing(struct kvm_vm *vm)
+{
+	struct kvm_irq_routing routing = {};
+
+	vm_ioctl(vm, KVM_SET_GSI_ROUTING, &routing);
+}
+
 static const char *probe_iommu_type(void)
 {
 	int io_fd;
@@ -139,11 +146,12 @@ static const char *probe_iommu_type(void)
 
 static void help(const char *name)
 {
-	printf("Usage: %s [-a] [-d <segment:bus:device.function>] [-h] [-t iommu_type]\n", name);
+	printf("Usage: %s [-a] [-d <segment:bus:device.function>] [-e] [-h] [-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("-t	Override the IOMMU type to use (vfio_type1_iommu or iommufd)\n");
 	printf("\n");
 	exit(KSFT_FAIL);
@@ -170,6 +178,7 @@ int main(int argc, char **argv)
 	struct kvm_vcpu *vcpus[KVM_MAX_VCPUS];
 	struct vfio_pci_device *device = NULL;
 	int nr_irqs = 1000, nr_vcpus = 1;
+	bool set_empty_routing = false;
 	const char *device_bdf = NULL;
 	const char *iommu_type = NULL;
 	int i, j, c, msix, eventfd;
@@ -177,7 +186,7 @@ int main(int argc, char **argv)
 	struct kvm_vm *vm;
 	int irq, irq_cpu;
 
-	while ((c = getopt(argc, argv, "ad:ht:")) != -1) {
+	while ((c = getopt(argc, argv, "ad:eht:")) != -1) {
 		switch (c) {
 		case 'a':
 			irq_affinity = true;
@@ -185,6 +194,9 @@ int main(int argc, char **argv)
 		case 'd':
 			device_bdf = optarg;
 			break;
+		case 'e':
+			set_empty_routing = true;
+			break;
 		case 't':
 			iommu_type = optarg;
 			break;
@@ -234,9 +246,13 @@ int main(int argc, char **argv)
 	}
 
 	for (i = 0; i < nr_irqs; i++) {
+		const bool do_set_empty_routing = set_empty_routing && (i & BIT(3));
 		struct kvm_vcpu *vcpu = vcpus[i % nr_vcpus];
 		struct timespec start;
 
+		if (do_set_empty_routing)
+			kvm_set_empty_gsi_routing(vm);
+
 		kvm_route_msi(vm, gsi, vcpu, vector);
 
 		if (irq_affinity) {
-- 
2.55.0.rc0.799.gd6f94ed593-goog