[PATCH v4 16/19] KVM: selftests: Verify vCPU migration during IRQ delivery in IRQ test

[Josh Hilke <jrhilke@google.com>]

Add the '-m' flag to tools/testing/selftests/kvm/irq_test.c to migrate
vCPU threads across random physical CPUs during the test. This validates
KVM's ability to handle vCPUs changing physical CPUs while interrupts
are actively being injected.

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 | 34 ++++++++++++++++++++++++--
 1 file changed, 32 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/kvm/irq_test.c b/tools/testing/selftests/kvm/irq_test.c
index 79b0691c9889..f653317022e3 100644
--- a/tools/testing/selftests/kvm/irq_test.c
+++ b/tools/testing/selftests/kvm/irq_test.c
@@ -18,6 +18,8 @@ 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 guest_received_nmi[KVM_MAX_VCPUS];
+static pid_t vcpu_tids[KVM_MAX_VCPUS];
+static bool migrate_vcpus;
 static bool irq_affinity;
 static bool block_vcpus;
 static bool done;
@@ -67,12 +69,23 @@ static void *vcpu_thread_main(void *arg)
 	struct kvm_vcpu *vcpu = arg;
 	struct ucall uc;
 
+	WRITE_ONCE(vcpu_tids[vcpu->id], kvm_gettid());
+
 	vcpu_run(vcpu);
 	TEST_ASSERT_EQ(UCALL_DONE, get_ucall(vcpu, &uc));
 
 	return NULL;
 }
 
+static void migrate_vcpu_threads(int nr_vcpus, pthread_t *vcpu_threads,
+				 cpu_set_t *available_cpus)
+{
+	int i;
+
+	for (i = 0; i < nr_vcpus; i++)
+		pin_task_to_random_cpu(vcpu_threads[i], available_cpus);
+}
+
 static int vfio_setup_msi(struct vfio_pci_device *device)
 {
 	const int flags = MAP_SHARED | MAP_ANONYMOUS;
@@ -131,7 +144,7 @@ static void kvm_clear_gsi_routes(struct kvm_vm *vm)
 
 static void help(const char *name)
 {
-	printf("Usage: %s [-a] [-b] [-c] [-d <segment:bus:device.function>] [-h] [-i nr_irqs] [-n]\n", name);
+	printf("Usage: %s [-a] [-b] [-c] [-d <segment:bus:device.function>] [-h] [-i nr_irqs] [-m] [-n]\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");
@@ -139,6 +152,7 @@ static void help(const char *name)
 	printf("-c	Destroy and recreate KVM's GSI routing table in between some interrupts\n");
 	printf("-d	Use a VFIO device to send MSI-X interrupts instead of using an emulated eventfd\n");
 	printf("-i	The number of IRQs to generate during the test\n");
+	printf("-m	Pin vCPU threads to random physical CPUs throughout the test\n");
 	printf("-n	Deliver 50 percent of IRQs as non-maskable interrupts\n");
 	printf("\n");
 	exit(KSFT_FAIL);
@@ -171,8 +185,9 @@ int main(int argc, char **argv)
 	FILE *irq_affinity_fp = NULL;
 	struct iommu *iommu;
 	struct kvm_vm *vm;
+	cpu_set_t available_cpus;
 
-	while ((c = getopt(argc, argv, "abcd:hi:n")) != -1) {
+	while ((c = getopt(argc, argv, "abcd:hi:mn")) != -1) {
 		switch (c) {
 		case 'a':
 			irq_affinity = true;
@@ -189,6 +204,9 @@ 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;
@@ -238,6 +256,15 @@ int main(int argc, char **argv)
 			continue;
 	}
 
+	if (migrate_vcpus) {
+		kvm_sched_getaffinity(vcpu_tids[0], sizeof(available_cpus), &available_cpus);
+
+		if (nr_vcpus > CPU_COUNT(&available_cpus)) {
+			printf("There are more vCPUs than pCPUs; refusing to migrate.\n");
+			migrate_vcpus = false;
+		}
+	}
+
 	for (i = 0; i < nr_irqs; i++) {
 		const bool do_clear_routes = clear_routes && (i & BIT(3));
 		const bool do_use_nmi = use_nmi && (i & BIT(2));
@@ -254,6 +281,9 @@ int main(int argc, char **argv)
 			write_proc_irq_affinity(irq_affinity_fp, irq, irq_cpu);
 		}
 
+		if (migrate_vcpus && vcpu->id == 0)
+			migrate_vcpu_threads(nr_vcpus, vcpu_threads, &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",
-- 
2.54.0.929.g9b7fa37559-goog