[PATCH v5 10/21] KVM: selftests: Verify interrupts are received when IRQ affinity changes in IRQ test

[Josh Hilke <jrhilke@google.com>]

From: David Matlack <dmatlack@google.com>

Add the '-a' flag to tools/testing/selftests/kvm/irq_test.c to randomly
affinitize the device's host IRQ to different physical CPUs throughout
the test. This stresses the kernel's ability to maintain correct
interrupt routing and delivery even as the underlying hardware IRQ
affinity is changed dynamically via /proc/irq/.

Co-developed-by: Josh Hilke <jrhilke@google.com>
Signed-off-by: Josh Hilke <jrhilke@google.com>
Signed-off-by: David Matlack <dmatlack@google.com>
---
 tools/testing/selftests/kvm/irq_test.c | 41 ++++++++++++++++++++++++--
 1 file changed, 38 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/kvm/irq_test.c b/tools/testing/selftests/kvm/irq_test.c
index 5b42d8abd1ea..90cff165c351 100644
--- a/tools/testing/selftests/kvm/irq_test.c
+++ b/tools/testing/selftests/kvm/irq_test.c
@@ -11,11 +11,13 @@
 #include <unistd.h>
 #include <pthread.h>
 #include <sys/eventfd.h>
+#include <sys/sysinfo.h>
 #include <libvfio.h>
 
 static u64 timeout_ns = 2ULL * 1000 * 1000 * 1000;
 static bool guest_ready_for_irqs[KVM_MAX_VCPUS];
 static bool guest_received_irq[KVM_MAX_VCPUS];
+static bool irq_affinity;
 static bool done;
 
 #define GUEST_RECEIVED_IRQ(__vcpu)	\
@@ -109,9 +111,10 @@ static void kvm_route_msi(struct kvm_vm *vm, u32 gsi, struct kvm_vcpu *vcpu,
 
 static void help(const char *name)
 {
-	printf("Usage: %s [-d <segment:bus:device.function>] [-h]\n", name);
+	printf("Usage: %s [-a] [-d <segment:bus:device.function>] [-h]\n", name);
 	printf("\n");
 	printf("Tests KVM IRQ injection via irqfd using an emulated eventfd.\n");
+	printf("-a	Randomly affinitize the device's host IRQ to different physical CPUs throughout the test\n");
 	printf("-d	Use a VFIO device to send MSI-X interrupts instead of using an emulated eventfd\n");
 	printf("\n");
 	exit(KSFT_FAIL);
@@ -139,13 +142,18 @@ int main(int argc, char **argv)
 	struct vfio_pci_device *device = NULL;
 	int nr_irqs = 1000, nr_vcpus = 1;
 	const char *device_bdf = NULL;
+	FILE *irq_affinity_fp = NULL;
 	int i, j, c, msix, eventfd;
 	struct iommu *iommu;
 	struct kvm_vm *vm;
 	unsigned int irq;
+	int irq_cpu;
 
-	while ((c = getopt(argc, argv, "d:h")) != -1) {
+	while ((c = getopt(argc, argv, "ad:h")) != -1) {
 		switch (c) {
+		case 'a':
+			irq_affinity = true;
+			break;
 		case 'd':
 			device_bdf = optarg;
 			break;
@@ -168,7 +176,11 @@ int main(int argc, char **argv)
 		eventfd = device->msi_eventfds[msix];
 		printf("Using device %s MSI-X[%d] (IRQ-%u)\n", device_bdf, msix,
 		       irq);
+		if (irq_affinity)
+			irq_affinity_fp = open_proc_irq_smp_affinity_list(irq);
 	} else {
+		TEST_ASSERT(!irq_affinity,
+			    "Setting IRQ affinity (-a) requires a backing device (-d)");
 		eventfd = kvm_new_eventfd();
 	}
 
@@ -187,12 +199,23 @@ int main(int argc, char **argv)
 			continue;
 	}
 
+	/*
+	 * Suppress a false positive maybe-uninitialized compiler warning due
+	 * to conditional changes in IRQ affinity.
+	 */
+	irq_cpu = -1;
+
 	for (i = 0; i < nr_irqs; i++) {
 		struct kvm_vcpu *vcpu = vcpus[i % nr_vcpus];
 		struct timespec start;
 
 		kvm_route_msi(vm, gsi, vcpu, vector);
 
+		if (irq_affinity_fp) {
+			irq_cpu = kvm_random_u64(&kvm_rng) % get_nprocs();
+			write_proc_irq_smp_affinity_list(irq_affinity_fp, irq, irq_cpu);
+		}
+
 		for (j = 0; j < nr_vcpus; j++)
 			TEST_ASSERT(!GUEST_RECEIVED_IRQ(vcpus[j]),
 				    "IRQ flag for vCPU %d not clear prior to test",
@@ -205,9 +228,18 @@ int main(int argc, char **argv)
 			if (GUEST_RECEIVED_IRQ(vcpu))
 				break;
 
-			if (timespec_to_ns(timespec_elapsed(start)) > timeout_ns)
+			if (timespec_to_ns(timespec_elapsed(start)) > timeout_ns) {
+				printf("Timeout waiting for interrupt!\n");
+				printf("  vCPU: %d\n", vcpu->id);
+				if (irq_affinity_fp) {
+					printf("  irq_cpu: %d\n", irq_cpu);
+					print_proc_irq_smp_affinity(irq);
+					print_proc_irq_effective_affinity(irq);
+				}
+
 				TEST_FAIL("vCPU %d timed out waiting for IRQ from GSI %d (Vector 0x%x) !\n",
 					  vcpu->id, gsi, vector);
+			}
 		}
 
 		WRITE_AND_SYNC_TO_GUEST(vm, guest_received_irq[vcpu->id], false);
@@ -218,6 +250,9 @@ int main(int argc, char **argv)
 	for (i = 0; i < nr_vcpus; i++)
 		pthread_join(vcpu_threads[i], NULL);
 
+	if (irq_affinity_fp)
+		fclose(irq_affinity_fp);
+
 	printf("Test passed!\n");
 
 	return 0;
-- 
2.54.0.1032.g2f8565e1d1-goog