KVM: selftests: Add stress test for LPI injection

Now that all the infrastructure is in place, add a test to stress KVM's
LPI injection. Keep a 1:1 mapping of device IDs to signalling threads,
allowing the user to scale up/down the sender side of an LPI. Make use
of the new VM stats for the translation cache to estimate the
translation hit rate.

Since the primary focus of the test is on performance, you'll notice
that the guest code is not pedantic about the LPIs it receives. Counting
the number of LPIs would require synchronization between the device and
vCPU threads to avoid coalescing and would get in the way of performance
numbers.

Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Link: https://lore.kernel.org/r/20240422200158.2606761-20-oliver.upton@linux.dev
Signed-off-by: Marc Zyngier <maz@kernel.org>

2 files changed, 411 insertions, 0 deletions

diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
index 4335e5744cc6..e78cac712229 100644
--- a/tools/testing/selftests/kvm/Makefile
+++ b/tools/testing/selftests/kvm/Makefile
@@ -158,6 +158,7 @@ TEST_GEN_PROGS_aarch64 += aarch64/smccc_filter
 TEST_GEN_PROGS_aarch64 += aarch64/vcpu_width_config
 TEST_GEN_PROGS_aarch64 += aarch64/vgic_init
 TEST_GEN_PROGS_aarch64 += aarch64/vgic_irq
+TEST_GEN_PROGS_aarch64 += aarch64/vgic_lpi_stress
 TEST_GEN_PROGS_aarch64 += aarch64/vpmu_counter_access
 TEST_GEN_PROGS_aarch64 += access_tracking_perf_test
 TEST_GEN_PROGS_aarch64 += arch_timer
diff --git a/tools/testing/selftests/kvm/aarch64/vgic_lpi_stress.c b/tools/testing/selftests/kvm/aarch64/vgic_lpi_stress.c
new file mode 100644
index 000000000000..fc4fe52fb6f8
--- /dev/null
+++ b/tools/testing/selftests/kvm/aarch64/vgic_lpi_stress.c
@@ -0,0 +1,410 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * vgic_lpi_stress - Stress test for KVM's ITS emulation
+ *
+ * Copyright (c) 2024 Google LLC
+ */
+
+#include <linux/sizes.h>
+#include <pthread.h>
+#include <stdatomic.h>
+#include <sys/sysinfo.h>
+
+#include "kvm_util.h"
+#include "gic.h"
+#include "gic_v3.h"
+#include "gic_v3_its.h"
+#include "processor.h"
+#include "ucall.h"
+#include "vgic.h"
+
+#define TEST_MEMSLOT_INDEX	1
+
+#define GIC_LPI_OFFSET	8192
+
+static size_t nr_iterations = 1000;
+static vm_paddr_t gpa_base;
+
+static struct kvm_vm *vm;
+static struct kvm_vcpu **vcpus;
+static int gic_fd, its_fd;
+
+static struct test_data {
+	bool		request_vcpus_stop;
+	u32		nr_cpus;
+	u32		nr_devices;
+	u32		nr_event_ids;
+
+	vm_paddr_t	device_table;
+	vm_paddr_t	collection_table;
+	vm_paddr_t	cmdq_base;
+	void		*cmdq_base_va;
+	vm_paddr_t	itt_tables;
+
+	vm_paddr_t	lpi_prop_table;
+	vm_paddr_t	lpi_pend_tables;
+} test_data =  {
+	.nr_cpus	= 1,
+	.nr_devices	= 1,
+	.nr_event_ids	= 16,
+};
+
+static void guest_irq_handler(struct ex_regs *regs)
+{
+	u32 intid = gic_get_and_ack_irq();
+
+	if (intid == IAR_SPURIOUS)
+		return;
+
+	GUEST_ASSERT(intid >= GIC_LPI_OFFSET);
+	gic_set_eoi(intid);
+}
+
+static void guest_setup_its_mappings(void)
+{
+	u32 coll_id, device_id, event_id, intid = GIC_LPI_OFFSET;
+	u32 nr_events = test_data.nr_event_ids;
+	u32 nr_devices = test_data.nr_devices;
+	u32 nr_cpus = test_data.nr_cpus;
+
+	for (coll_id = 0; coll_id < nr_cpus; coll_id++)
+		its_send_mapc_cmd(test_data.cmdq_base_va, coll_id, coll_id, true);
+
+	/* Round-robin the LPIs to all of the vCPUs in the VM */
+	coll_id = 0;
+	for (device_id = 0; device_id < nr_devices; device_id++) {
+		vm_paddr_t itt_base = test_data.itt_tables + (device_id * SZ_64K);
+
+		its_send_mapd_cmd(test_data.cmdq_base_va, device_id,
+				  itt_base, SZ_64K, true);
+
+		for (event_id = 0; event_id < nr_events; event_id++) {
+			its_send_mapti_cmd(test_data.cmdq_base_va, device_id,
+					   event_id, coll_id, intid++);
+
+			coll_id = (coll_id + 1) % test_data.nr_cpus;
+		}
+	}
+}
+
+static void guest_invalidate_all_rdists(void)
+{
+	int i;
+
+	for (i = 0; i < test_data.nr_cpus; i++)
+		its_send_invall_cmd(test_data.cmdq_base_va, i);
+}
+
+static void guest_setup_gic(void)
+{
+	static atomic_int nr_cpus_ready = 0;
+	u32 cpuid = guest_get_vcpuid();
+
+	gic_init(GIC_V3, test_data.nr_cpus);
+	gic_rdist_enable_lpis(test_data.lpi_prop_table, SZ_64K,
+			      test_data.lpi_pend_tables + (cpuid * SZ_64K));
+
+	atomic_fetch_add(&nr_cpus_ready, 1);
+
+	if (cpuid > 0)
+		return;
+
+	while (atomic_load(&nr_cpus_ready) < test_data.nr_cpus)
+		cpu_relax();
+
+	its_init(test_data.collection_table, SZ_64K,
+		 test_data.device_table, SZ_64K,
+		 test_data.cmdq_base, SZ_64K);
+
+	guest_setup_its_mappings();
+	guest_invalidate_all_rdists();
+}
+
+static void guest_code(size_t nr_lpis)
+{
+	guest_setup_gic();
+
+	GUEST_SYNC(0);
+
+	/*
+	 * Don't use WFI here to avoid blocking the vCPU thread indefinitely and
+	 * never getting the stop signal.
+	 */
+	while (!READ_ONCE(test_data.request_vcpus_stop))
+		cpu_relax();
+
+	GUEST_DONE();
+}
+
+static void setup_memslot(void)
+{
+	size_t pages;
+	size_t sz;
+
+	/*
+	 * For the ITS:
+	 *  - A single level device table
+	 *  - A single level collection table
+	 *  - The command queue
+	 *  - An ITT for each device
+	 */
+	sz = (3 + test_data.nr_devices) * SZ_64K;
+
+	/*
+	 * For the redistributors:
+	 *  - A shared LPI configuration table
+	 *  - An LPI pending table for each vCPU
+	 */
+	sz += (1 + test_data.nr_cpus) * SZ_64K;
+
+	pages = sz / vm->page_size;
+	gpa_base = ((vm_compute_max_gfn(vm) + 1) * vm->page_size) - sz;
+	vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS, gpa_base,
+				    TEST_MEMSLOT_INDEX, pages, 0);
+}
+
+#define LPI_PROP_DEFAULT_PRIO	0xa0
+
+static void configure_lpis(void)
+{
+	size_t nr_lpis = test_data.nr_devices * test_data.nr_event_ids;
+	u8 *tbl = addr_gpa2hva(vm, test_data.lpi_prop_table);
+	size_t i;
+
+	for (i = 0; i < nr_lpis; i++) {
+		tbl[i] = LPI_PROP_DEFAULT_PRIO |
+			 LPI_PROP_GROUP1 |
+			 LPI_PROP_ENABLED;
+	}
+}
+
+static void setup_test_data(void)
+{
+	size_t pages_per_64k = vm_calc_num_guest_pages(vm->mode, SZ_64K);
+	u32 nr_devices = test_data.nr_devices;
+	u32 nr_cpus = test_data.nr_cpus;
+	vm_paddr_t cmdq_base;
+
+	test_data.device_table = vm_phy_pages_alloc(vm, pages_per_64k,
+						    gpa_base,
+						    TEST_MEMSLOT_INDEX);
+
+	test_data.collection_table = vm_phy_pages_alloc(vm, pages_per_64k,
+							gpa_base,
+							TEST_MEMSLOT_INDEX);
+
+	cmdq_base = vm_phy_pages_alloc(vm, pages_per_64k, gpa_base,
+				       TEST_MEMSLOT_INDEX);
+	virt_map(vm, cmdq_base, cmdq_base, pages_per_64k);
+	test_data.cmdq_base = cmdq_base;
+	test_data.cmdq_base_va = (void *)cmdq_base;
+
+	test_data.itt_tables = vm_phy_pages_alloc(vm, pages_per_64k * nr_devices,
+						  gpa_base, TEST_MEMSLOT_INDEX);
+
+	test_data.lpi_prop_table = vm_phy_pages_alloc(vm, pages_per_64k,
+						      gpa_base, TEST_MEMSLOT_INDEX);
+	configure_lpis();
+
+	test_data.lpi_pend_tables = vm_phy_pages_alloc(vm, pages_per_64k * nr_cpus,
+						       gpa_base, TEST_MEMSLOT_INDEX);
+
+	sync_global_to_guest(vm, test_data);
+}
+
+static void setup_gic(void)
+{
+	gic_fd = vgic_v3_setup(vm, test_data.nr_cpus, 64);
+	__TEST_REQUIRE(gic_fd >= 0, "Failed to create GICv3");
+
+	its_fd = vgic_its_setup(vm);
+}
+
+static void signal_lpi(u32 device_id, u32 event_id)
+{
+	vm_paddr_t db_addr = GITS_BASE_GPA + GITS_TRANSLATER;
+
+	struct kvm_msi msi = {
+		.address_lo	= db_addr,
+		.address_hi	= db_addr >> 32,
+		.data		= event_id,
+		.devid		= device_id,
+		.flags		= KVM_MSI_VALID_DEVID,
+	};
+
+	/*
+	 * KVM_SIGNAL_MSI returns 1 if the MSI wasn't 'blocked' by the VM,
+	 * which for arm64 implies having a valid translation in the ITS.
+	 */
+	TEST_ASSERT(__vm_ioctl(vm, KVM_SIGNAL_MSI, &msi) == 1,
+		    "KVM_SIGNAL_MSI ioctl failed");
+}
+
+static pthread_barrier_t test_setup_barrier;
+
+static void *lpi_worker_thread(void *data)
+{
+	u32 device_id = (size_t)data;
+	u32 event_id;
+	size_t i;
+
+	pthread_barrier_wait(&test_setup_barrier);
+
+	for (i = 0; i < nr_iterations; i++)
+		for (event_id = 0; event_id < test_data.nr_event_ids; event_id++)
+			signal_lpi(device_id, event_id);
+
+	return NULL;
+}
+
+static void *vcpu_worker_thread(void *data)
+{
+	struct kvm_vcpu *vcpu = data;
+	struct ucall uc;
+
+	while (true) {
+		vcpu_run(vcpu);
+
+		switch (get_ucall(vcpu, &uc)) {
+		case UCALL_SYNC:
+			pthread_barrier_wait(&test_setup_barrier);
+			continue;
+		case UCALL_DONE:
+			return NULL;
+		case UCALL_ABORT:
+			REPORT_GUEST_ASSERT(uc);
+			break;
+		default:
+			TEST_FAIL("Unknown ucall: %lu", uc.cmd);
+		}
+	}
+
+	return NULL;
+}
+
+static void report_stats(struct timespec delta)
+{
+	double nr_lpis;
+	double time;
+
+	nr_lpis = test_data.nr_devices * test_data.nr_event_ids * nr_iterations;
+
+	time = delta.tv_sec;
+	time += ((double)delta.tv_nsec) / NSEC_PER_SEC;
+
+	pr_info("Rate: %.2f LPIs/sec\n", nr_lpis / time);
+}
+
+static void run_test(void)
+{
+	u32 nr_devices = test_data.nr_devices;
+	u32 nr_vcpus = test_data.nr_cpus;
+	pthread_t *lpi_threads = malloc(nr_devices * sizeof(pthread_t));
+	pthread_t *vcpu_threads = malloc(nr_vcpus * sizeof(pthread_t));
+	struct timespec start, delta;
+	size_t i;
+
+	TEST_ASSERT(lpi_threads && vcpu_threads, "Failed to allocate pthread arrays");
+
+	pthread_barrier_init(&test_setup_barrier, NULL, nr_vcpus + nr_devices + 1);
+
+	for (i = 0; i < nr_vcpus; i++)
+		pthread_create(&vcpu_threads[i], NULL, vcpu_worker_thread, vcpus[i]);
+
+	for (i = 0; i < nr_devices; i++)
+		pthread_create(&lpi_threads[i], NULL, lpi_worker_thread, (void *)i);
+
+	pthread_barrier_wait(&test_setup_barrier);
+
+	clock_gettime(CLOCK_MONOTONIC, &start);
+
+	for (i = 0; i < nr_devices; i++)
+		pthread_join(lpi_threads[i], NULL);
+
+	delta = timespec_elapsed(start);
+	write_guest_global(vm, test_data.request_vcpus_stop, true);
+
+	for (i = 0; i < nr_vcpus; i++)
+		pthread_join(vcpu_threads[i], NULL);
+
+	report_stats(delta);
+}
+
+static void setup_vm(void)
+{
+	int i;
+
+	vcpus = malloc(test_data.nr_cpus * sizeof(struct kvm_vcpu));
+	TEST_ASSERT(vcpus, "Failed to allocate vCPU array");
+
+	vm = vm_create_with_vcpus(test_data.nr_cpus, guest_code, vcpus);
+
+	vm_init_descriptor_tables(vm);
+	for (i = 0; i < test_data.nr_cpus; i++)
+		vcpu_init_descriptor_tables(vcpus[i]);
+
+	vm_install_exception_handler(vm, VECTOR_IRQ_CURRENT, guest_irq_handler);
+
+	setup_memslot();
+
+	setup_gic();
+
+	setup_test_data();
+}
+
+static void destroy_vm(void)
+{
+	close(its_fd);
+	close(gic_fd);
+	kvm_vm_free(vm);
+	free(vcpus);
+}
+
+static void pr_usage(const char *name)
+{
+	pr_info("%s [-v NR_VCPUS] [-d NR_DEVICES] [-e NR_EVENTS] [-i ITERS] -h\n", name);
+	pr_info("  -v:\tnumber of vCPUs (default: %u)\n", test_data.nr_cpus);
+	pr_info("  -d:\tnumber of devices (default: %u)\n", test_data.nr_devices);
+	pr_info("  -e:\tnumber of event IDs per device (default: %u)\n", test_data.nr_event_ids);
+	pr_info("  -i:\tnumber of iterations (default: %lu)\n", nr_iterations);
+}
+
+int main(int argc, char **argv)
+{
+	u32 nr_threads;
+	int c;
+
+	while ((c = getopt(argc, argv, "hv:d:e:i:")) != -1) {
+		switch (c) {
+		case 'v':
+			test_data.nr_cpus = atoi(optarg);
+			break;
+		case 'd':
+			test_data.nr_devices = atoi(optarg);
+			break;
+		case 'e':
+			test_data.nr_event_ids = atoi(optarg);
+			break;
+		case 'i':
+			nr_iterations = strtoul(optarg, NULL, 0);
+			break;
+		case 'h':
+		default:
+			pr_usage(argv[0]);
+			return 1;
+		}
+	}
+
+	nr_threads = test_data.nr_cpus + test_data.nr_devices;
+	if (nr_threads > get_nprocs())
+		pr_info("WARNING: running %u threads on %d CPUs; performance is degraded.\n",
+			 nr_threads, get_nprocs());
+
+	setup_vm();
+
+	run_test();
+
+	destroy_vm();
+
+	return 0;
+}