sched_ext: Maintain an online cid mask in the scheduler arenagrafted

Schedulers on the default cid mapping treat [0, nr_online_cids) as the
online set and restart on hotplug. Schedulers that install their own mapping
with scx_bpf_cid_override() have no way to learn which cids are online: the
count no longer identifies members and the CPU-form cpumask is unusable from
cid programs. This is an obvious hole in the cid API.

Add scx_bpf_online_cmask(), a kernel-maintained cmask in the scheduler's
arena, allocated alongside the per-CPU scratch masks and populated after the
cid mapping is finalized and before ops.init(), for child schedulers too.
The pointer stays valid through ops.exit() with no reference to take. It is
the arena offset as a void pointer, the same form struct_ops arena arguments
arrive in. The verifier types the void return as a scalar for the program's
arena cast.

The mask follows the SCX hotplug notifications: seeded from cpu_active_mask
and updated before ops.cid_online/offline() runs, so it lags cpu_online_mask
only inside a hotplug transition. Updates walk the scheduler list under the
lock that also serializes unlinking. Reads are live, not atomic snapshots.
Root initialization excludes hotplug.

v2: Reworded the getter kerneldoc (Andrea Righi).

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>

1 files changed, 281 insertions, 0 deletions

diff --git a/drivers/opp/debugfs.c b/drivers/opp/debugfs.c
new file mode 100644
index 000000000..61506d30d
--- /dev/null
+++ b/drivers/opp/debugfs.c
@@ -0,0 +1,281 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Generic OPP debugfs interface
+ *
+ * Copyright (C) 2015-2016 Viresh Kumar <viresh.kumar@linaro.org>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/debugfs.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/of.h>
+#include <linux/init.h>
+#include <linux/limits.h>
+#include <linux/slab.h>
+
+#include "opp.h"
+
+static struct dentry *rootdir;
+
+static void opp_set_dev_name(const struct device *dev, char *name)
+{
+	if (dev->parent)
+		snprintf(name, NAME_MAX, "%s-%s", dev_name(dev->parent),
+			 dev_name(dev));
+	else
+		snprintf(name, NAME_MAX, "%s", dev_name(dev));
+}
+
+void opp_debug_remove_one(struct dev_pm_opp *opp)
+{
+	debugfs_remove_recursive(opp->dentry);
+}
+
+static ssize_t bw_name_read(struct file *fp, char __user *userbuf,
+			    size_t count, loff_t *ppos)
+{
+	struct icc_path *path = fp->private_data;
+	const char *name = icc_get_name(path);
+	char buf[64];
+	int i = 0;
+
+	if (name)
+		i = scnprintf(buf, sizeof(buf), "%.62s\n", name);
+
+	return simple_read_from_buffer(userbuf, count, ppos, buf, i);
+}
+
+static const struct file_operations bw_name_fops = {
+	.open = simple_open,
+	.read = bw_name_read,
+	.llseek = default_llseek,
+};
+
+static void opp_debug_create_bw(struct dev_pm_opp *opp,
+				struct opp_table *opp_table,
+				struct dentry *pdentry)
+{
+	struct dentry *d;
+	char name[] = "icc-path-XXXXXXXXXXX"; /* Integers can take 11 chars max */
+	int i;
+
+	for (i = 0; i < opp_table->path_count; i++) {
+		snprintf(name, sizeof(name), "icc-path-%d", i);
+
+		/* Create per-path directory */
+		d = debugfs_create_dir(name, pdentry);
+
+		debugfs_create_file("name", S_IRUGO, d, opp_table->paths[i],
+				    &bw_name_fops);
+		debugfs_create_u32("peak_bw", S_IRUGO, d,
+				   &opp->bandwidth[i].peak);
+		debugfs_create_u32("avg_bw", S_IRUGO, d,
+				   &opp->bandwidth[i].avg);
+	}
+}
+
+static void opp_debug_create_clks(struct dev_pm_opp *opp,
+				  struct opp_table *opp_table,
+				  struct dentry *pdentry)
+{
+	char name[] = "rate_hz_XXXXXXXXXXX"; /* Integers can take 11 chars max */
+	int i;
+
+	if (opp_table->clk_count == 1) {
+		debugfs_create_ulong("rate_hz", S_IRUGO, pdentry, &opp->rates[0]);
+		return;
+	}
+
+	for (i = 0; i < opp_table->clk_count; i++) {
+		snprintf(name, sizeof(name), "rate_hz_%d", i);
+		debugfs_create_ulong(name, S_IRUGO, pdentry, &opp->rates[i]);
+	}
+}
+
+static void opp_debug_create_supplies(struct dev_pm_opp *opp,
+				      struct opp_table *opp_table,
+				      struct dentry *pdentry)
+{
+	struct dentry *d;
+	int i;
+
+	for (i = 0; i < opp_table->regulator_count; i++) {
+		char name[] = "supply-XXXXXXXXXXX"; /* Integers can take 11 chars max */
+
+		snprintf(name, sizeof(name), "supply-%d", i);
+
+		/* Create per-opp directory */
+		d = debugfs_create_dir(name, pdentry);
+
+		debugfs_create_ulong("u_volt_target", S_IRUGO, d,
+				     &opp->supplies[i].u_volt);
+
+		debugfs_create_ulong("u_volt_min", S_IRUGO, d,
+				     &opp->supplies[i].u_volt_min);
+
+		debugfs_create_ulong("u_volt_max", S_IRUGO, d,
+				     &opp->supplies[i].u_volt_max);
+
+		debugfs_create_ulong("u_amp", S_IRUGO, d,
+				     &opp->supplies[i].u_amp);
+
+		debugfs_create_ulong("u_watt", S_IRUGO, d,
+				     &opp->supplies[i].u_watt);
+	}
+}
+
+void opp_debug_create_one(struct dev_pm_opp *opp, struct opp_table *opp_table)
+{
+	struct dentry *pdentry = opp_table->dentry;
+	struct dentry *d;
+	char name[36];	/* "opp:"(4) + u64(20) + "-" (1) + u32(10) + NULL(1) */
+
+	/*
+	 * Get directory name for OPP.
+	 *
+	 * - Normally rate is unique to each OPP, use it to get unique opp-name,
+	 *   together with performance level if available.
+	 * - For some devices rate isn't available or there are multiple, use
+	 *   index instead for them.
+	 */
+	if (likely(opp_table->clk_count == 1 && opp->rates[0])) {
+		if (opp->level == OPP_LEVEL_UNSET)
+			snprintf(name, sizeof(name), "opp:%lu", opp->rates[0]);
+		else
+			snprintf(name, sizeof(name), "opp:%lu-%u", opp->rates[0], opp->level);
+	} else {
+		snprintf(name, sizeof(name), "opp:%u", _get_opp_count(opp_table));
+	}
+
+	/* Create per-opp directory */
+	d = debugfs_create_dir(name, pdentry);
+
+	debugfs_create_bool("available", S_IRUGO, d, &opp->available);
+	debugfs_create_bool("dynamic", S_IRUGO, d, &opp->dynamic);
+	debugfs_create_bool("turbo", S_IRUGO, d, &opp->turbo);
+	debugfs_create_bool("suspend", S_IRUGO, d, &opp->suspend);
+	debugfs_create_u32("level", S_IRUGO, d, &opp->level);
+	debugfs_create_ulong("clock_latency_ns", S_IRUGO, d,
+			     &opp->clock_latency_ns);
+
+	opp->of_name = of_node_full_name(opp->np);
+	debugfs_create_str("of_name", S_IRUGO, d, (char **)&opp->of_name);
+
+	opp_debug_create_clks(opp, opp_table, d);
+	opp_debug_create_supplies(opp, opp_table, d);
+	opp_debug_create_bw(opp, opp_table, d);
+
+	opp->dentry = d;
+}
+
+static void opp_list_debug_create_dir(struct opp_device *opp_dev,
+				      struct opp_table *opp_table)
+{
+	const struct device *dev = opp_dev->dev;
+	struct dentry *d;
+
+	opp_set_dev_name(dev, opp_table->dentry_name);
+
+	/* Create device specific directory */
+	d = debugfs_create_dir(opp_table->dentry_name, rootdir);
+
+	opp_dev->dentry = d;
+	opp_table->dentry = d;
+}
+
+static void opp_list_debug_create_link(struct opp_device *opp_dev,
+				       struct opp_table *opp_table)
+{
+	char name[NAME_MAX];
+
+	opp_set_dev_name(opp_dev->dev, name);
+
+	/* Create device specific directory link */
+	opp_dev->dentry = debugfs_create_symlink(name, rootdir,
+						 opp_table->dentry_name);
+}
+
+/**
+ * opp_debug_register - add a device opp node to the debugfs 'opp' directory
+ * @opp_dev: opp-dev pointer for device
+ * @opp_table: the device-opp being added
+ *
+ * Dynamically adds device specific directory in debugfs 'opp' directory. If the
+ * device-opp is shared with other devices, then links will be created for all
+ * devices except the first.
+ */
+void opp_debug_register(struct opp_device *opp_dev, struct opp_table *opp_table)
+{
+	if (opp_table->dentry)
+		opp_list_debug_create_link(opp_dev, opp_table);
+	else
+		opp_list_debug_create_dir(opp_dev, opp_table);
+}
+
+static void opp_migrate_dentry(struct opp_device *opp_dev,
+			       struct opp_table *opp_table)
+{
+	struct opp_device *new_dev = NULL, *iter;
+	const struct device *dev;
+	int err;
+
+	/* Look for next opp-dev */
+	list_for_each_entry(iter, &opp_table->dev_list, node)
+		if (iter != opp_dev) {
+			new_dev = iter;
+			break;
+		}
+
+	BUG_ON(!new_dev);
+
+	/* new_dev is guaranteed to be valid here */
+	dev = new_dev->dev;
+	debugfs_remove_recursive(new_dev->dentry);
+
+	opp_set_dev_name(dev, opp_table->dentry_name);
+
+	err = debugfs_change_name(opp_dev->dentry, "%s", opp_table->dentry_name);
+	if (err) {
+		dev_err(dev, "%s: Failed to rename link from: %s to %s\n",
+			__func__, dev_name(opp_dev->dev), dev_name(dev));
+		return;
+	}
+
+	new_dev->dentry = opp_table->dentry = opp_dev->dentry;
+}
+
+/**
+ * opp_debug_unregister - remove a device opp node from debugfs opp directory
+ * @opp_dev: opp-dev pointer for device
+ * @opp_table: the device-opp being removed
+ *
+ * Dynamically removes device specific directory from debugfs 'opp' directory.
+ */
+void opp_debug_unregister(struct opp_device *opp_dev,
+			  struct opp_table *opp_table)
+{
+	if (opp_dev->dentry == opp_table->dentry) {
+		/* Move the real dentry object under another device */
+		if (!list_is_singular(&opp_table->dev_list)) {
+			opp_migrate_dentry(opp_dev, opp_table);
+			goto out;
+		}
+		opp_table->dentry = NULL;
+	}
+
+	debugfs_remove_recursive(opp_dev->dentry);
+
+out:
+	opp_dev->dentry = NULL;
+}
+
+static int __init opp_debug_init(void)
+{
+	/* Create /sys/kernel/debug/opp directory */
+	rootdir = debugfs_create_dir("opp", NULL);
+
+	return 0;
+}
+core_initcall(opp_debug_init);