riscv: Add parameter for skipping access speed tests

Allow skipping scalar and vector unaligned access speed tests. This
is useful for testing alternative code paths and to skip the tests in
environments where they run too slowly. All CPUs must have the same
unaligned access speed.

The code movement is because we now need the scalar cpu hotplug
callback to always run, so we need to bring it and its supporting
functions out of CONFIG_RISCV_PROBE_UNALIGNED_ACCESS.

Signed-off-by: Andrew Jones <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Alexandre Ghiti <[email protected]>

Author: Andrew Jones

arch/riscv/kernel/unaligned_access_speed.c

@@ -24,8 +24,12 @@
 DEFINE_PER_CPU(long, misaligned_access_speed) = RISCV_HWPROBE_MISALIGNED_SCALAR_UNKNOWN;
 DEFINE_PER_CPU(long, vector_misaligned_access) = RISCV_HWPROBE_MISALIGNED_VECTOR_UNSUPPORTED;
 
-#ifdef CONFIG_RISCV_PROBE_UNALIGNED_ACCESS
+static long unaligned_scalar_speed_param = RISCV_HWPROBE_MISALIGNED_SCALAR_UNKNOWN;
+static long unaligned_vector_speed_param = RISCV_HWPROBE_MISALIGNED_VECTOR_UNKNOWN;
+
 static cpumask_t fast_misaligned_access;
+
+#ifdef CONFIG_RISCV_PROBE_UNALIGNED_ACCESS
 static int check_unaligned_access(void *param)
 {
 	int cpu = smp_processor_id();
@@ -130,6 +134,50 @@ static void __init check_unaligned_access_nonboot_cpu(void *param)
 		check_unaligned_access(pages[cpu]);
 }
 
+/* Measure unaligned access speed on all CPUs present at boot in parallel. */
+static void __init check_unaligned_access_speed_all_cpus(void)
+{
+	unsigned int cpu;
+	unsigned int cpu_count = num_possible_cpus();
+	struct page **bufs = kcalloc(cpu_count, sizeof(*bufs), GFP_KERNEL);
+
+	if (!bufs) {
+		pr_warn("Allocation failure, not measuring misaligned performance\n");
+		return;
+	}
+
+	/*
+	 * Allocate separate buffers for each CPU so there's no fighting over
+	 * cache lines.
+	 */
+	for_each_cpu(cpu, cpu_online_mask) {
+		bufs[cpu] = alloc_pages(GFP_KERNEL, MISALIGNED_BUFFER_ORDER);
+		if (!bufs[cpu]) {
+			pr_warn("Allocation failure, not measuring misaligned performance\n");
+			goto out;
+		}
+	}
+
+	/* Check everybody except 0, who stays behind to tend jiffies. */
+	on_each_cpu(check_unaligned_access_nonboot_cpu, bufs, 1);
+
+	/* Check core 0. */
+	smp_call_on_cpu(0, check_unaligned_access, bufs[0], true);
+
+out:
+	for_each_cpu(cpu, cpu_online_mask) {
+		if (bufs[cpu])
+			__free_pages(bufs[cpu], MISALIGNED_BUFFER_ORDER);
+	}
+
+	kfree(bufs);
+}
+#else /* CONFIG_RISCV_PROBE_UNALIGNED_ACCESS */
+static void __init check_unaligned_access_speed_all_cpus(void)
+{
+}
+#endif
+
 DEFINE_STATIC_KEY_FALSE(fast_unaligned_access_speed_key);
 
 static void modify_unaligned_access_branches(cpumask_t *mask, int weight)
@@ -188,21 +236,29 @@ arch_initcall_sync(lock_and_set_unaligned_access_static_branch);
 
 static int riscv_online_cpu(unsigned int cpu)
 {
-	static struct page *buf;
-
 	/* We are already set since the last check */
-	if (per_cpu(misaligned_access_speed, cpu) != RISCV_HWPROBE_MISALIGNED_SCALAR_UNKNOWN)
+	if (per_cpu(misaligned_access_speed, cpu) != RISCV_HWPROBE_MISALIGNED_SCALAR_UNKNOWN) {
+		goto exit;
+	} else if (unaligned_scalar_speed_param != RISCV_HWPROBE_MISALIGNED_SCALAR_UNKNOWN) {
+		per_cpu(misaligned_access_speed, cpu) = unaligned_scalar_speed_param;
 		goto exit;
-
-	check_unaligned_access_emulated(NULL);
-	buf = alloc_pages(GFP_KERNEL, MISALIGNED_BUFFER_ORDER);
-	if (!buf) {
-		pr_warn("Allocation failure, not measuring misaligned performance\n");
-		return -ENOMEM;
 	}
 
-	check_unaligned_access(buf);
-	__free_pages(buf, MISALIGNED_BUFFER_ORDER);
+#ifdef CONFIG_RISCV_PROBE_UNALIGNED_ACCESS
+	{
+		static struct page *buf;
+
+		check_unaligned_access_emulated(NULL);
+		buf = alloc_pages(GFP_KERNEL, MISALIGNED_BUFFER_ORDER);
+		if (!buf) {
+			pr_warn("Allocation failure, not measuring misaligned performance\n");
+			return -ENOMEM;
+		}
+
+		check_unaligned_access(buf);
+		__free_pages(buf, MISALIGNED_BUFFER_ORDER);
+	}
+#endif
 
 exit:
 	set_unaligned_access_static_branches();
@@ -217,50 +273,6 @@ static int riscv_offline_cpu(unsigned int cpu)
 	return 0;
 }
 
-/* Measure unaligned access speed on all CPUs present at boot in parallel. */
-static void __init check_unaligned_access_speed_all_cpus(void)
-{
-	unsigned int cpu;
-	unsigned int cpu_count = num_possible_cpus();
-	struct page **bufs = kcalloc(cpu_count, sizeof(*bufs), GFP_KERNEL);
-
-	if (!bufs) {
-		pr_warn("Allocation failure, not measuring misaligned performance\n");
-		return;
-	}
-
-	/*
-	 * Allocate separate buffers for each CPU so there's no fighting over
-	 * cache lines.
-	 */
-	for_each_cpu(cpu, cpu_online_mask) {
-		bufs[cpu] = alloc_pages(GFP_KERNEL, MISALIGNED_BUFFER_ORDER);
-		if (!bufs[cpu]) {
-			pr_warn("Allocation failure, not measuring misaligned performance\n");
-			goto out;
-		}
-	}
-
-	/* Check everybody except 0, who stays behind to tend jiffies. */
-	on_each_cpu(check_unaligned_access_nonboot_cpu, bufs, 1);
-
-	/* Check core 0. */
-	smp_call_on_cpu(0, check_unaligned_access, bufs[0], true);
-
-out:
-	for_each_cpu(cpu, cpu_online_mask) {
-		if (bufs[cpu])
-			__free_pages(bufs[cpu], MISALIGNED_BUFFER_ORDER);
-	}
-
-	kfree(bufs);
-}
-#else /* CONFIG_RISCV_PROBE_UNALIGNED_ACCESS */
-static void __init check_unaligned_access_speed_all_cpus(void)
-{
-}
-#endif
-
 #ifdef CONFIG_RISCV_PROBE_VECTOR_UNALIGNED_ACCESS
 static void check_vector_unaligned_access(struct work_struct *work __always_unused)
 {
@@ -372,8 +384,8 @@ static int __init vec_check_unaligned_access_speed_all_cpus(void *unused __alway
 
 static int riscv_online_cpu_vec(unsigned int cpu)
 {
-	if (!has_vector()) {
-		per_cpu(vector_misaligned_access, cpu) = RISCV_HWPROBE_MISALIGNED_VECTOR_UNSUPPORTED;
+	if (unaligned_vector_speed_param != RISCV_HWPROBE_MISALIGNED_VECTOR_UNKNOWN) {
+		per_cpu(vector_misaligned_access, cpu) = unaligned_vector_speed_param;
 		return 0;
 	}
 
@@ -388,30 +400,73 @@ static int riscv_online_cpu_vec(unsigned int cpu)
 	return 0;
 }
 
+static const char * const speed_str[] __initconst = { NULL, NULL, "slow", "fast", "unsupported" };
+
+static int __init set_unaligned_scalar_speed_param(char *str)
+{
+	if (!strcmp(str, speed_str[RISCV_HWPROBE_MISALIGNED_SCALAR_SLOW]))
+		unaligned_scalar_speed_param = RISCV_HWPROBE_MISALIGNED_SCALAR_SLOW;
+	else if (!strcmp(str, speed_str[RISCV_HWPROBE_MISALIGNED_SCALAR_FAST]))
+		unaligned_scalar_speed_param = RISCV_HWPROBE_MISALIGNED_SCALAR_FAST;
+	else if (!strcmp(str, speed_str[RISCV_HWPROBE_MISALIGNED_SCALAR_UNSUPPORTED]))
+		unaligned_scalar_speed_param = RISCV_HWPROBE_MISALIGNED_SCALAR_UNSUPPORTED;
+	else
+		return -EINVAL;
+
+	return 1;
+}
+__setup("unaligned_scalar_speed=", set_unaligned_scalar_speed_param);
+
+static int __init set_unaligned_vector_speed_param(char *str)
+{
+	if (!strcmp(str, speed_str[RISCV_HWPROBE_MISALIGNED_VECTOR_SLOW]))
+		unaligned_vector_speed_param = RISCV_HWPROBE_MISALIGNED_VECTOR_SLOW;
+	else if (!strcmp(str, speed_str[RISCV_HWPROBE_MISALIGNED_VECTOR_FAST]))
+		unaligned_vector_speed_param = RISCV_HWPROBE_MISALIGNED_VECTOR_FAST;
+	else if (!strcmp(str, speed_str[RISCV_HWPROBE_MISALIGNED_VECTOR_UNSUPPORTED]))
+		unaligned_vector_speed_param = RISCV_HWPROBE_MISALIGNED_VECTOR_UNSUPPORTED;
+	else
+		return -EINVAL;
+
+	return 1;
+}
+__setup("unaligned_vector_speed=", set_unaligned_vector_speed_param);
+
 static int __init check_unaligned_access_all_cpus(void)
 {
 	int cpu;
 
-	if (!check_unaligned_access_emulated_all_cpus())
+	if (unaligned_scalar_speed_param == RISCV_HWPROBE_MISALIGNED_SCALAR_UNKNOWN &&
+	    !check_unaligned_access_emulated_all_cpus()) {
 		check_unaligned_access_speed_all_cpus();
-
-	if (!has_vector()) {
+	} else {
+		pr_info("scalar unaligned access speed set to '%s' by command line\n",
+			speed_str[unaligned_scalar_speed_param]);
 		for_each_online_cpu(cpu)
-			per_cpu(vector_misaligned_access, cpu) = RISCV_HWPROBE_MISALIGNED_VECTOR_UNSUPPORTED;
-	} else if (!check_vector_unaligned_access_emulated_all_cpus() &&
-		   IS_ENABLED(CONFIG_RISCV_PROBE_VECTOR_UNALIGNED_ACCESS)) {
+			per_cpu(misaligned_access_speed, cpu) = unaligned_scalar_speed_param;
+	}
+
+	if (!has_vector())
+		unaligned_vector_speed_param = RISCV_HWPROBE_MISALIGNED_VECTOR_UNSUPPORTED;
+
+	if (unaligned_vector_speed_param == RISCV_HWPROBE_MISALIGNED_VECTOR_UNKNOWN &&
+	    !check_vector_unaligned_access_emulated_all_cpus() &&
+	    IS_ENABLED(CONFIG_RISCV_PROBE_VECTOR_UNALIGNED_ACCESS)) {
 		kthread_run(vec_check_unaligned_access_speed_all_cpus,
 			    NULL, "vec_check_unaligned_access_speed_all_cpus");
+	} else {
+		pr_info("vector unaligned access speed set to '%s' by command line\n",
+			speed_str[unaligned_vector_speed_param]);
+		for_each_online_cpu(cpu)
+			per_cpu(vector_misaligned_access, cpu) = unaligned_vector_speed_param;
 	}
 
 	/*
 	 * Setup hotplug callbacks for any new CPUs that come online or go
 	 * offline.
 	 */
-#ifdef CONFIG_RISCV_PROBE_UNALIGNED_ACCESS
 	cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "riscv:online",
 				  riscv_online_cpu, riscv_offline_cpu);
-#endif
 	cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "riscv:online",
 				  riscv_online_cpu_vec, NULL);