[PATCH v3 06/16] KVM: selftests: Add IRQ injection test

[Josh Hilke]

From: David Matlack <dmatlack@xxxxxxxxxx>

Add a new test, irq_test.c, which verifies that KVM correctly injects
interrupts into a running guest when triggered via an eventfd bound to a
GSI using the irqfd mechanism.

Suggested-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Link: https://lore.kernel.org/kvm/20250404193923.1413163-68-seanjc@xxxxxxxxxx/
Co-developed-by: Josh Hilke <jrhilke@xxxxxxxxxx>
Signed-off-by: Josh Hilke <jrhilke@xxxxxxxxxx>
Signed-off-by: David Matlack <dmatlack@xxxxxxxxxx>
---
 tools/testing/selftests/kvm/Makefile.kvm |   1 +
 tools/testing/selftests/kvm/irq_test.c   | 173 +++++++++++++++++++++++
 2 files changed, 174 insertions(+)
 create mode 100644 tools/testing/selftests/kvm/irq_test.c

diff --git a/tools/testing/selftests/kvm/Makefile.kvm b/tools/testing/selftests/kvm/Makefile.kvm
index d944b81cad7d..693c03372a31 100644
--- a/tools/testing/selftests/kvm/Makefile.kvm
+++ b/tools/testing/selftests/kvm/Makefile.kvm
@@ -156,6 +156,7 @@ TEST_GEN_PROGS_x86 += rseq_test
 TEST_GEN_PROGS_x86 += steal_time
 TEST_GEN_PROGS_x86 += system_counter_offset_test
 TEST_GEN_PROGS_x86 += pre_fault_memory_test
+TEST_GEN_PROGS_x86 += irq_test
 
 # Compiled outputs used by test targets
 TEST_GEN_PROGS_EXTENDED_x86 += x86/nx_huge_pages_test
diff --git a/tools/testing/selftests/kvm/irq_test.c b/tools/testing/selftests/kvm/irq_test.c
new file mode 100644
index 000000000000..317e04899df3
--- /dev/null
+++ b/tools/testing/selftests/kvm/irq_test.c
@@ -0,0 +1,173 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "kvm_util.h"
+#include "test_util.h"
+#include "apic.h"
+#include "processor.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <pthread.h>
+#include <sys/eventfd.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 done;
+
+static u32 guest_get_vcpu_id(void)
+{
+	return x2apic_read_reg(APIC_ID);
+}
+
+static void guest_irq_handler(struct ex_regs *regs)
+{
+	WRITE_ONCE(guest_received_irq[guest_get_vcpu_id()], true);
+
+	x2apic_write_reg(APIC_EOI, 0);
+}
+
+static void guest_code(void)
+{
+	x2apic_enable();
+
+	sti_nop();
+
+	WRITE_ONCE(guest_ready_for_irqs[guest_get_vcpu_id()], true);
+
+	while (!READ_ONCE(done))
+		cpu_relax();
+
+	GUEST_DONE();
+}
+
+static void *vcpu_thread_main(void *arg)
+{
+	struct kvm_vcpu *vcpu = arg;
+	struct ucall uc;
+
+	vcpu_run(vcpu);
+	TEST_ASSERT_EQ(UCALL_DONE, get_ucall(vcpu, &uc));
+
+	return NULL;
+}
+
+static void kvm_route_msi(struct kvm_vm *vm, u32 gsi, struct kvm_vcpu *vcpu,
+			  u8 vector)
+{
+	struct {
+		struct kvm_irq_routing head;
+		struct kvm_irq_routing_entry entry;
+	} routing_data = {};
+
+	struct kvm_irq_routing *routes = &routing_data.head;
+
+	routes->nr = 1;
+	routes->entries[0].gsi = gsi;
+	routes->entries[0].type = KVM_IRQ_ROUTING_MSI;
+	routes->entries[0].u.msi.address_lo = 0xFEE00000 | (vcpu->id << 12);
+	routes->entries[0].u.msi.data = vector;
+
+	vm_ioctl(vm, KVM_SET_GSI_ROUTING, routes);
+}
+
+static void help(const char *name)
+{
+	printf("Usage: %s [-h]\n", name);
+	printf("\n");
+	printf("Tests KVM IRQ injection via irqfd using an emulated eventfd.\n");
+	printf("\n");
+	exit(KSFT_FAIL);
+}
+
+int main(int argc, char **argv)
+{
+	/*
+	 * Pick a random vector and a random GSI to use for device IRQ.
+	 *
+	 * Pick an IRQ vector in range [32, UINT8_MAX]. Min value is 32 because
+	 * Linux/x86 reserves vectors 0-31 for exceptions and architecture
+	 * defined NMIs and interrupts.
+	 *
+	 * Pick a GSI in range [24, KVM_MAX_IRQ_ROUTES - 1]. The min value is 24
+	 * because KVM reserves GSIs 0-15 for legacy ISA IRQs and 16-23 only go
+	 * to the IOAPIC. The max is KVM_MAX_IRQ_ROUTES - 1, because
+	 * KVM_MAX_IRQ_ROUTES is exclusive.
+	 */
+	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];
+	int nr_irqs = 1000, nr_vcpus = 1;
+	int i, j, c, eventfd;
+	struct kvm_vm *vm;
+
+	while ((c = getopt(argc, argv, "h")) != -1) {
+		switch (c) {
+		case 'h':
+		default:
+			help(argv[0]);
+		}
+	}
+
+	TEST_REQUIRE(kvm_arch_has_default_irqchip());
+
+	vm = vm_create_with_vcpus(nr_vcpus, guest_code, vcpus);
+	vm_install_exception_handler(vm, vector, guest_irq_handler);
+
+	eventfd = kvm_new_eventfd();
+
+	printf("Injecting interrupts for GSI %d (Vector 0x%x) %d times\n",
+	       gsi, vector, nr_irqs);
+
+	kvm_assign_irqfd(vm, gsi, eventfd);
+
+	for (i = 0; i < nr_vcpus; i++)
+		pthread_create(&vcpu_threads[i], NULL, vcpu_thread_main, vcpus[i]);
+
+	for (i = 0; i < nr_vcpus; i++) {
+		struct kvm_vcpu *vcpu = vcpus[i];
+
+		while (!SYNC_FROM_GUEST_AND_READ(vm, guest_ready_for_irqs[vcpu->id]))
+			continue;
+	}
+
+	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);
+
+		for (j = 0; j < nr_vcpus; j++)
+			TEST_ASSERT(
+				!SYNC_FROM_GUEST_AND_READ(vm, guest_received_irq[vcpus[j]->id]),
+				"IRQ flag for vCPU %d not clear prior to test",
+				vcpus[j]->id);
+
+		/* Trigger interrupt */
+		eventfd_write(eventfd, 1);
+
+		clock_gettime(CLOCK_MONOTONIC, &start);
+		for (;;) {
+			if (SYNC_FROM_GUEST_AND_READ(vm, guest_received_irq[vcpu->id]))
+				break;
+
+			if (timespec_to_ns(timespec_elapsed(start)) > timeout_ns)
+				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);
+	}
+
+	WRITE_AND_SYNC_TO_GUEST(vm, done, true);
+
+	for (i = 0; i < nr_vcpus; i++)
+		pthread_join(vcpu_threads[i], NULL);
+
+	printf("Test passed!\n");
+
+	return 0;
+}
-- 
2.54.0.rc2.533.g4f5dca5207-goog