KVM: arm64: selftests: get-reg-list: Provide config selection option

Add a new command line option that allows the user to select a specific
configuration, e.g. --config=sve will give the sve config. Also provide
help text and the --help/-h options.
Signed-off-by: NAndrew Jones <drjones@redhat.com>
Reviewed-by: NRicardo Koller <ricarkol@google.com>
Signed-off-by: NMarc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210531103344.29325-4-drjones@redhat.com

tools/testing/selftests/kvm/aarch64/get-reg-list.c

@@ -539,6 +539,52 @@ static void run_test(struct vcpu_config *c)
 	kvm_vm_free(vm);
 }
 
+static void help(void)
+{
+	struct vcpu_config *c;
+	int i;
+
+	printf(
+	"\n"
+	"usage: get-reg-list [--config=<selection>] [--list] [--list-filtered] [--core-reg-fixup]\n\n"
+	" --config=<selection>        Used to select a specific vcpu configuration for the test/listing\n"
+	"                             '<selection>' may be\n");
+
+	for (i = 0; i < vcpu_configs_n; ++i) {
+		c = vcpu_configs[i];
+		printf(
+	"                               '%s'\n", config_name(c));
+	}
+
+	printf(
+	"\n"
+	" --list                      Print the register list rather than test it (requires --config)\n"
+	" --list-filtered             Print registers that would normally be filtered out (requires --config)\n"
+	" --core-reg-fixup            Needed when running on old kernels with broken core reg listings\n"
+	"\n"
+	);
+}
+
+static struct vcpu_config *parse_config(const char *config)
+{
+	struct vcpu_config *c;
+	int i;
+
+	if (config[8] != '=')
+		help(), exit(1);
+
+	for (i = 0; i < vcpu_configs_n; ++i) {
+		c = vcpu_configs[i];
+		if (strcmp(config_name(c), &config[9]) == 0)
+			break;
+	}
+
+	if (i == vcpu_configs_n)
+		help(), exit(1);
+
+	return c;
+}
+
 int main(int ac, char **av)
 {
 	struct vcpu_config *c, *sel = NULL;
@@ -547,20 +593,24 @@ int main(int ac, char **av)
 	for (i = 1; i < ac; ++i) {
 		if (strcmp(av[i], "--core-reg-fixup") == 0)
 			fixup_core_regs = true;
+		else if (strncmp(av[i], "--config", 8) == 0)
+			sel = parse_config(av[i]);
 		else if (strcmp(av[i], "--list") == 0)
 			print_list = true;
 		else if (strcmp(av[i], "--list-filtered") == 0)
 			print_filtered = true;
+		else if (strcmp(av[i], "--help") == 0 || strcmp(av[1], "-h") == 0)
+			help(), exit(0);
 		else
-			TEST_FAIL("Unknown option: %s\n", av[i]);
+			help(), exit(1);
 	}
 
 	if (print_list || print_filtered) {
 		/*
 		 * We only want to print the register list of a single config.
-		 * TODO: Add command line support to pick which config.
 		 */
-		sel = vcpu_configs[0];
+		if (!sel)
+			help(), exit(1);
 	}
 
 	for (i = 0; i < vcpu_configs_n; ++i) {