KVM: arm64: selftests: Augment existing timer test to handle variable offset

Allow a user to specify the global offset on the command-line.
Reviewed-by: Colton Lewis <coltonlewis@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20230330174800.2677007-21-maz@kernel.org

tools/testing/selftests/kvm/aarch64/arch_timer.c

@@ -47,6 +47,7 @@ struct test_args {
 	int nr_iter;
 	int timer_period_ms;
 	int migration_freq_ms;
+	struct kvm_arm_counter_offset offset;
 };
 
 static struct test_args test_args = {
@@ -54,6 +55,7 @@ static struct test_args test_args = {
 	.nr_iter = NR_TEST_ITERS_DEF,
 	.timer_period_ms = TIMER_TEST_PERIOD_MS_DEF,
 	.migration_freq_ms = TIMER_TEST_MIGRATION_FREQ_MS,
+	.offset = { .reserved = 1 },
 };
 
 #define msecs_to_usecs(msec)		((msec) * 1000LL)
@@ -382,6 +384,13 @@ static struct kvm_vm *test_vm_create(void)
 	vm_init_descriptor_tables(vm);
 	vm_install_exception_handler(vm, VECTOR_IRQ_CURRENT, guest_irq_handler);
 
+	if (!test_args.offset.reserved) {
+		if (kvm_has_cap(KVM_CAP_COUNTER_OFFSET))
+			vm_ioctl(vm, KVM_ARM_SET_COUNTER_OFFSET, &test_args.offset);
+		else
+			TEST_FAIL("no support for global offset\n");
+	}
+
 	for (i = 0; i < nr_vcpus; i++)
 		vcpu_init_descriptor_tables(vcpus[i]);
 
@@ -413,6 +422,7 @@ static void test_print_help(char *name)
 		TIMER_TEST_PERIOD_MS_DEF);
 	pr_info("\t-m: Frequency (in ms) of vCPUs to migrate to different pCPU. 0 to turn off (default: %u)\n",
 		TIMER_TEST_MIGRATION_FREQ_MS);
+	pr_info("\t-o: Counter offset (in counter cycles, default: 0)\n");
 	pr_info("\t-h: print this help screen\n");
 }
 
@@ -420,7 +430,7 @@ static bool parse_args(int argc, char *argv[])
 {
 	int opt;
 
-	while ((opt = getopt(argc, argv, "hn:i:p:m:")) != -1) {
+	while ((opt = getopt(argc, argv, "hn:i:p:m:o:")) != -1) {
 		switch (opt) {
 		case 'n':
 			test_args.nr_vcpus = atoi_positive("Number of vCPUs", optarg);
@@ -439,6 +449,10 @@ static bool parse_args(int argc, char *argv[])
 		case 'm':
 			test_args.migration_freq_ms = atoi_non_negative("Frequency", optarg);
 			break;
+		case 'o':
+			test_args.offset.counter_offset = strtol(optarg, NULL, 0);
+			test_args.offset.reserved = 0;
+			break;
 		case 'h':
 		default:
 			goto err;