[PATCH v5 05/21] KVM: selftests: Add IRQ injection test

[Josh Hilke <jrhilke@google.com>]

From: David Matlack <dmatlack@google.com>

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.

This test is intentionally simple. Support for IRQ bypass, receiving
interrupts from real devices, and other features will be added to this
test in future changes.

Suggested-by: Sean Christopherson <seanjc@google.com>
Link: https://lore.kernel.org/kvm/20250404193923.1413163-68-seanjc@google.com/
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/Makefile.kvm |   2 +
 tools/testing/selftests/kvm/irq_test.c   | 174 +++++++++++++++++++++++
 2 files changed, 176 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 2da11e1f3d9a..b859098121c7 100644
--- a/tools/testing/selftests/kvm/Makefile.kvm
+++ b/tools/testing/selftests/kvm/Makefile.kvm
@@ -153,12 +153,14 @@ TEST_GEN_PROGS_x86 += coalesced_io_test
 TEST_GEN_PROGS_x86 += dirty_log_perf_test
 TEST_GEN_PROGS_x86 += guest_memfd_test
 TEST_GEN_PROGS_x86 += hardware_disable_test
+TEST_GEN_PROGS_x86 += irq_test
 TEST_GEN_PROGS_x86 += mmu_stress_test
 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
 
+
 # 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..d3fee51cf451
--- /dev/null
+++ b/tools/testing/selftests/kvm/irq_test.c
@@ -0,0 +1,174 @@
+// 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;
+
+#define GUEST_RECEIVED_IRQ(__vcpu)	\
+	SYNC_FROM_GUEST_AND_READ((__vcpu)->vm, guest_received_irq[(__vcpu)->id])
+
+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(!GUEST_RECEIVED_IRQ(vcpus[j]),
+				    "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 (GUEST_RECEIVED_IRQ(vcpu))
+				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;
+}
-- 
2.54.0.1032.g2f8565e1d1-goog