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, 693 insertions, 0 deletions

diff --git a/drivers/video/fbdev/simplefb.c b/drivers/video/fbdev/simplefb.c
new file mode 100644
index 000000000..60e5dcec2
--- /dev/null
+++ b/drivers/video/fbdev/simplefb.c
@@ -0,0 +1,693 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Simplest possible simple frame-buffer driver, as a platform device
+ *
+ * Copyright (c) 2013, Stephen Warren
+ *
+ * Based on q40fb.c, which was:
+ * Copyright (C) 2001 Richard Zidlicky <rz@linux-m68k.org>
+ *
+ * Also based on offb.c, which was:
+ * Copyright (C) 1997 Geert Uytterhoeven
+ * Copyright (C) 1996 Paul Mackerras
+ */
+
+#include <linux/aperture.h>
+#include <linux/clk.h>
+#include <linux/errno.h>
+#include <linux/fb.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_clk.h>
+#include <linux/of_platform.h>
+#include <linux/of_reserved_mem.h>
+#include <linux/parser.h>
+#include <linux/platform_data/simplefb.h>
+#include <linux/platform_device.h>
+#include <linux/pm_domain.h>
+#include <linux/regulator/consumer.h>
+
+static const struct fb_fix_screeninfo simplefb_fix = {
+	.id		= "simple",
+	.type		= FB_TYPE_PACKED_PIXELS,
+	.visual		= FB_VISUAL_TRUECOLOR,
+	.accel		= FB_ACCEL_NONE,
+};
+
+static const struct fb_var_screeninfo simplefb_var = {
+	.height		= -1,
+	.width		= -1,
+	.activate	= FB_ACTIVATE_NOW,
+	.vmode		= FB_VMODE_NONINTERLACED,
+};
+
+#define PSEUDO_PALETTE_SIZE 16
+
+static int simplefb_setcolreg(u_int regno, u_int red, u_int green, u_int blue,
+			      u_int transp, struct fb_info *info)
+{
+	u32 *pal = info->pseudo_palette;
+	u32 cr = red >> (16 - info->var.red.length);
+	u32 cg = green >> (16 - info->var.green.length);
+	u32 cb = blue >> (16 - info->var.blue.length);
+	u32 value;
+
+	if (regno >= PSEUDO_PALETTE_SIZE)
+		return -EINVAL;
+
+	value = (cr << info->var.red.offset) |
+		(cg << info->var.green.offset) |
+		(cb << info->var.blue.offset);
+	if (info->var.transp.length > 0) {
+		u32 mask = (1 << info->var.transp.length) - 1;
+		mask <<= info->var.transp.offset;
+		value |= mask;
+	}
+	pal[regno] = value;
+
+	return 0;
+}
+
+struct simplefb_par {
+	u32 palette[PSEUDO_PALETTE_SIZE];
+	resource_size_t base;
+	resource_size_t size;
+	struct resource *mem;
+#if defined CONFIG_OF && defined CONFIG_COMMON_CLK
+	bool clks_enabled;
+	unsigned int clk_count;
+	struct clk **clks;
+#endif
+#if defined CONFIG_OF && defined CONFIG_PM_GENERIC_DOMAINS
+	unsigned int num_genpds;
+	struct device **genpds;
+	struct device_link **genpd_links;
+#endif
+#if defined CONFIG_OF && defined CONFIG_REGULATOR
+	bool regulators_enabled;
+	u32 regulator_count;
+	struct regulator **regulators;
+#endif
+};
+
+static void simplefb_clocks_destroy(struct simplefb_par *par);
+static void simplefb_regulators_destroy(struct simplefb_par *par);
+static void simplefb_detach_genpds(void *res);
+
+/*
+ * fb_ops.fb_destroy is called by the last put_fb_info() call at the end
+ * of unregister_framebuffer() or fb_release(). Do any cleanup here.
+ */
+static void simplefb_destroy(struct fb_info *info)
+{
+	struct simplefb_par *par = info->par;
+	struct resource *mem = par->mem;
+
+	simplefb_regulators_destroy(info->par);
+	simplefb_clocks_destroy(info->par);
+	simplefb_detach_genpds(info->par);
+	if (info->screen_base)
+		iounmap(info->screen_base);
+
+	framebuffer_release(info);
+
+	if (mem)
+		release_mem_region(mem->start, resource_size(mem));
+}
+
+static const struct fb_ops simplefb_ops = {
+	.owner		= THIS_MODULE,
+	FB_DEFAULT_IOMEM_OPS,
+	.fb_destroy	= simplefb_destroy,
+	.fb_setcolreg	= simplefb_setcolreg,
+};
+
+static struct simplefb_format simplefb_formats[] = SIMPLEFB_FORMATS;
+
+struct simplefb_params {
+	u32 width;
+	u32 height;
+	u32 stride;
+	struct simplefb_format *format;
+	struct resource memory;
+};
+
+static int simplefb_parse_dt(struct platform_device *pdev,
+			   struct simplefb_params *params)
+{
+	struct device_node *np = pdev->dev.of_node;
+	int ret;
+	const char *format;
+	int i;
+
+	ret = of_property_read_u32(np, "width", &params->width);
+	if (ret) {
+		dev_err(&pdev->dev, "Can't parse width property\n");
+		return ret;
+	}
+
+	ret = of_property_read_u32(np, "height", &params->height);
+	if (ret) {
+		dev_err(&pdev->dev, "Can't parse height property\n");
+		return ret;
+	}
+
+	ret = of_property_read_u32(np, "stride", &params->stride);
+	if (ret) {
+		dev_err(&pdev->dev, "Can't parse stride property\n");
+		return ret;
+	}
+
+	ret = of_property_read_string(np, "format", &format);
+	if (ret) {
+		dev_err(&pdev->dev, "Can't parse format property\n");
+		return ret;
+	}
+	params->format = NULL;
+	for (i = 0; i < ARRAY_SIZE(simplefb_formats); i++) {
+		if (strcmp(format, simplefb_formats[i].name))
+			continue;
+		params->format = &simplefb_formats[i];
+		break;
+	}
+	if (!params->format) {
+		dev_err(&pdev->dev, "Invalid format value\n");
+		return -EINVAL;
+	}
+
+	ret = of_reserved_mem_region_to_resource(np, 0, &params->memory);
+	if (!ret) {
+		if (of_property_present(np, "reg"))
+			dev_warn(&pdev->dev, "preferring \"memory-region\" over \"reg\" property\n");
+	} else {
+		memset(&params->memory, 0, sizeof(params->memory));
+	}
+
+	return 0;
+}
+
+static int simplefb_parse_pd(struct platform_device *pdev,
+			     struct simplefb_params *params)
+{
+	struct simplefb_platform_data *pd = dev_get_platdata(&pdev->dev);
+	int i;
+
+	params->width = pd->width;
+	params->height = pd->height;
+	params->stride = pd->stride;
+
+	params->format = NULL;
+	for (i = 0; i < ARRAY_SIZE(simplefb_formats); i++) {
+		if (strcmp(pd->format, simplefb_formats[i].name))
+			continue;
+
+		params->format = &simplefb_formats[i];
+		break;
+	}
+
+	if (!params->format) {
+		dev_err(&pdev->dev, "Invalid format value\n");
+		return -EINVAL;
+	}
+
+	memset(&params->memory, 0, sizeof(params->memory));
+
+	return 0;
+}
+
+#if defined CONFIG_OF && defined CONFIG_COMMON_CLK
+/*
+ * Clock handling code.
+ *
+ * Here we handle the clocks property of our "simple-framebuffer" dt node.
+ * This is necessary so that we can make sure that any clocks needed by
+ * the display engine that the bootloader set up for us (and for which it
+ * provided a simplefb dt node), stay up, for the life of the simplefb
+ * driver.
+ *
+ * When the driver unloads, we cleanly disable, and then release the clocks.
+ *
+ * We only complain about errors here, no action is taken as the most likely
+ * error can only happen due to a mismatch between the bootloader which set
+ * up simplefb, and the clock definitions in the device tree. Chances are
+ * that there are no adverse effects, and if there are, a clean teardown of
+ * the fb probe will not help us much either. So just complain and carry on,
+ * and hope that the user actually gets a working fb at the end of things.
+ */
+static int simplefb_clocks_get(struct simplefb_par *par,
+			       struct platform_device *pdev)
+{
+	struct device_node *np = pdev->dev.of_node;
+	struct clk *clock;
+	int i;
+
+	if (dev_get_platdata(&pdev->dev) || !np)
+		return 0;
+
+	par->clk_count = of_clk_get_parent_count(np);
+	if (!par->clk_count)
+		return 0;
+
+	par->clks = kzalloc_objs(struct clk *, par->clk_count);
+	if (!par->clks)
+		return -ENOMEM;
+
+	for (i = 0; i < par->clk_count; i++) {
+		clock = of_clk_get(np, i);
+		if (IS_ERR(clock)) {
+			if (PTR_ERR(clock) == -EPROBE_DEFER) {
+				while (--i >= 0) {
+					clk_put(par->clks[i]);
+				}
+				kfree(par->clks);
+				return -EPROBE_DEFER;
+			}
+			dev_err(&pdev->dev, "%s: clock %d not found: %ld\n",
+				__func__, i, PTR_ERR(clock));
+			continue;
+		}
+		par->clks[i] = clock;
+	}
+
+	return 0;
+}
+
+static void simplefb_clocks_enable(struct simplefb_par *par,
+				   struct platform_device *pdev)
+{
+	int i, ret;
+
+	for (i = 0; i < par->clk_count; i++) {
+		if (par->clks[i]) {
+			ret = clk_prepare_enable(par->clks[i]);
+			if (ret) {
+				dev_err(&pdev->dev,
+					"%s: failed to enable clock %d: %d\n",
+					__func__, i, ret);
+				clk_put(par->clks[i]);
+				par->clks[i] = NULL;
+			}
+		}
+	}
+	par->clks_enabled = true;
+}
+
+static void simplefb_clocks_destroy(struct simplefb_par *par)
+{
+	int i;
+
+	if (!par->clks)
+		return;
+
+	for (i = 0; i < par->clk_count; i++) {
+		if (par->clks[i]) {
+			if (par->clks_enabled)
+				clk_disable_unprepare(par->clks[i]);
+			clk_put(par->clks[i]);
+		}
+	}
+
+	kfree(par->clks);
+}
+#else
+static int simplefb_clocks_get(struct simplefb_par *par,
+	struct platform_device *pdev) { return 0; }
+static void simplefb_clocks_enable(struct simplefb_par *par,
+	struct platform_device *pdev) { }
+static void simplefb_clocks_destroy(struct simplefb_par *par) { }
+#endif
+
+#if defined CONFIG_OF && defined CONFIG_REGULATOR
+
+#define SUPPLY_SUFFIX "-supply"
+
+/*
+ * Regulator handling code.
+ *
+ * Here we handle the num-supplies and vin*-supply properties of our
+ * "simple-framebuffer" dt node. This is necessary so that we can make sure
+ * that any regulators needed by the display hardware that the bootloader
+ * set up for us (and for which it provided a simplefb dt node), stay up,
+ * for the life of the simplefb driver.
+ *
+ * When the driver unloads, we cleanly disable, and then release the
+ * regulators.
+ *
+ * We only complain about errors here, no action is taken as the most likely
+ * error can only happen due to a mismatch between the bootloader which set
+ * up simplefb, and the regulator definitions in the device tree. Chances are
+ * that there are no adverse effects, and if there are, a clean teardown of
+ * the fb probe will not help us much either. So just complain and carry on,
+ * and hope that the user actually gets a working fb at the end of things.
+ */
+static int simplefb_regulators_get(struct simplefb_par *par,
+				   struct platform_device *pdev)
+{
+	struct device_node *np = pdev->dev.of_node;
+	struct property *prop;
+	struct regulator *regulator;
+	const char *p;
+	int count = 0, i = 0;
+
+	if (dev_get_platdata(&pdev->dev) || !np)
+		return 0;
+
+	/* Count the number of regulator supplies */
+	for_each_property_of_node(np, prop) {
+		p = strstr(prop->name, SUPPLY_SUFFIX);
+		if (p && p != prop->name)
+			count++;
+	}
+
+	if (!count)
+		return 0;
+
+	par->regulators = devm_kcalloc(&pdev->dev, count,
+				       sizeof(struct regulator *), GFP_KERNEL);
+	if (!par->regulators)
+		return -ENOMEM;
+
+	/* Get all the regulators */
+	for_each_property_of_node(np, prop) {
+		char name[32]; /* 32 is max size of property name */
+
+		p = strstr(prop->name, SUPPLY_SUFFIX);
+		if (!p || p == prop->name)
+			continue;
+
+		strscpy(name, prop->name,
+			strlen(prop->name) - strlen(SUPPLY_SUFFIX) + 1);
+		regulator = devm_regulator_get_optional(&pdev->dev, name);
+		if (IS_ERR(regulator)) {
+			if (PTR_ERR(regulator) == -EPROBE_DEFER)
+				return -EPROBE_DEFER;
+			dev_err(&pdev->dev, "regulator %s not found: %ld\n",
+				name, PTR_ERR(regulator));
+			continue;
+		}
+		par->regulators[i++] = regulator;
+	}
+	par->regulator_count = i;
+
+	return 0;
+}
+
+static void simplefb_regulators_enable(struct simplefb_par *par,
+				       struct platform_device *pdev)
+{
+	int i, ret;
+
+	/* Enable all the regulators */
+	for (i = 0; i < par->regulator_count; i++) {
+		ret = regulator_enable(par->regulators[i]);
+		if (ret) {
+			dev_err(&pdev->dev,
+				"failed to enable regulator %d: %d\n",
+				i, ret);
+			devm_regulator_put(par->regulators[i]);
+			par->regulators[i] = NULL;
+		}
+	}
+	par->regulators_enabled = true;
+}
+
+static void simplefb_regulators_destroy(struct simplefb_par *par)
+{
+	int i;
+
+	if (!par->regulators || !par->regulators_enabled)
+		return;
+
+	for (i = 0; i < par->regulator_count; i++)
+		if (par->regulators[i])
+			regulator_disable(par->regulators[i]);
+}
+#else
+static int simplefb_regulators_get(struct simplefb_par *par,
+	struct platform_device *pdev) { return 0; }
+static void simplefb_regulators_enable(struct simplefb_par *par,
+	struct platform_device *pdev) { }
+static void simplefb_regulators_destroy(struct simplefb_par *par) { }
+#endif
+
+#if defined CONFIG_OF && defined CONFIG_PM_GENERIC_DOMAINS
+static void simplefb_detach_genpds(void *res)
+{
+	struct simplefb_par *par = res;
+	unsigned int i = par->num_genpds;
+
+	if (par->num_genpds <= 1)
+		return;
+
+	while (i--) {
+		if (par->genpd_links[i])
+			device_link_del(par->genpd_links[i]);
+
+		if (!IS_ERR_OR_NULL(par->genpds[i]))
+			dev_pm_domain_detach(par->genpds[i], true);
+	}
+	par->num_genpds = 0;
+}
+
+static int simplefb_attach_genpds(struct simplefb_par *par,
+				  struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	unsigned int i, num_genpds;
+	int err;
+
+	err = of_count_phandle_with_args(dev->of_node, "power-domains",
+					 "#power-domain-cells");
+	if (err < 0) {
+		/* Nothing wrong if optional PDs are missing */
+		if (err == -ENOENT)
+			return 0;
+
+		dev_err(dev, "failed to parse power-domains: %d\n", err);
+		return err;
+	}
+
+	num_genpds = err;
+
+	/*
+	 * Single power-domain devices are handled by the driver core, so
+	 * nothing to do here.
+	 */
+	if (num_genpds <= 1) {
+		par->num_genpds = num_genpds;
+		return 0;
+	}
+
+	par->genpds = devm_kcalloc(dev, num_genpds, sizeof(*par->genpds),
+				   GFP_KERNEL);
+	if (!par->genpds)
+		return -ENOMEM;
+
+	par->genpd_links = devm_kcalloc(dev, num_genpds,
+					sizeof(*par->genpd_links),
+					GFP_KERNEL);
+	if (!par->genpd_links)
+		return -ENOMEM;
+
+	/*
+	 * Set par->num_genpds only after genpds and genpd_links are allocated
+	 * to exit early from simplefb_detach_genpds() without full
+	 * initialisation.
+	 */
+	par->num_genpds = num_genpds;
+
+	for (i = 0; i < par->num_genpds; i++) {
+		par->genpds[i] = dev_pm_domain_attach_by_id(dev, i);
+		if (IS_ERR(par->genpds[i])) {
+			err = PTR_ERR(par->genpds[i]);
+			if (err == -EPROBE_DEFER) {
+				simplefb_detach_genpds(par);
+				return err;
+			}
+
+			dev_warn(dev, "failed to attach domain %u: %d\n", i, err);
+			continue;
+		}
+
+		par->genpd_links[i] = device_link_add(dev, par->genpds[i],
+						      DL_FLAG_STATELESS |
+						      DL_FLAG_PM_RUNTIME |
+						      DL_FLAG_RPM_ACTIVE);
+		if (!par->genpd_links[i])
+			dev_warn(dev, "failed to link power-domain %u\n", i);
+	}
+
+	return 0;
+}
+#else
+static void simplefb_detach_genpds(void *res) { }
+static int simplefb_attach_genpds(struct simplefb_par *par,
+				  struct platform_device *pdev)
+{
+	return 0;
+}
+#endif
+
+static int simplefb_probe(struct platform_device *pdev)
+{
+	int ret;
+	struct simplefb_params params;
+	struct fb_info *info;
+	struct simplefb_par *par;
+	struct resource *res, *mem;
+
+	if (fb_get_options("simplefb", NULL))
+		return -ENODEV;
+
+	ret = -ENODEV;
+	if (dev_get_platdata(&pdev->dev))
+		ret = simplefb_parse_pd(pdev, &params);
+	else if (pdev->dev.of_node)
+		ret = simplefb_parse_dt(pdev, &params);
+
+	if (ret)
+		return ret;
+
+	if (params.memory.start == 0 && params.memory.end == 0) {
+		res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+		if (!res) {
+			dev_err(&pdev->dev, "No memory resource\n");
+			return -EINVAL;
+		}
+	} else {
+		res = &params.memory;
+	}
+
+	mem = request_mem_region(res->start, resource_size(res), "simplefb");
+	if (!mem) {
+		/*
+		 * We cannot make this fatal. Sometimes this comes from magic
+		 * spaces our resource handlers simply don't know about. Use
+		 * the I/O-memory resource as-is and try to map that instead.
+		 */
+		dev_warn(&pdev->dev, "simplefb: cannot reserve video memory at %pR\n", res);
+		mem = res;
+	}
+
+	info = framebuffer_alloc(sizeof(struct simplefb_par), &pdev->dev);
+	if (!info) {
+		ret = -ENOMEM;
+		goto error_release_mem_region;
+	}
+	platform_set_drvdata(pdev, info);
+
+	par = info->par;
+
+	info->fix = simplefb_fix;
+	info->fix.smem_start = mem->start;
+	info->fix.smem_len = resource_size(mem);
+	info->fix.line_length = params.stride;
+
+	info->var = simplefb_var;
+	info->var.xres = params.width;
+	info->var.yres = params.height;
+	info->var.xres_virtual = params.width;
+	info->var.yres_virtual = params.height;
+	info->var.bits_per_pixel = params.format->bits_per_pixel;
+	info->var.red = params.format->red;
+	info->var.green = params.format->green;
+	info->var.blue = params.format->blue;
+	info->var.transp = params.format->transp;
+
+	par->base = info->fix.smem_start;
+	par->size = info->fix.smem_len;
+
+	info->fbops = &simplefb_ops;
+	info->screen_base = ioremap_wc(info->fix.smem_start,
+				       info->fix.smem_len);
+	if (!info->screen_base) {
+		ret = -ENOMEM;
+		goto error_fb_release;
+	}
+	info->pseudo_palette = par->palette;
+
+	ret = simplefb_clocks_get(par, pdev);
+	if (ret < 0)
+		goto error_unmap;
+
+	ret = simplefb_regulators_get(par, pdev);
+	if (ret < 0)
+		goto error_clocks;
+
+	ret = simplefb_attach_genpds(par, pdev);
+	if (ret < 0)
+		goto error_regulators;
+
+	simplefb_clocks_enable(par, pdev);
+	simplefb_regulators_enable(par, pdev);
+
+	dev_info(&pdev->dev, "framebuffer at 0x%lx, 0x%x bytes\n",
+			     info->fix.smem_start, info->fix.smem_len);
+	dev_info(&pdev->dev, "format=%s, mode=%dx%dx%d, linelength=%d\n",
+			     params.format->name,
+			     info->var.xres, info->var.yres,
+			     info->var.bits_per_pixel, info->fix.line_length);
+
+	if (mem != res)
+		par->mem = mem; /* release in clean-up handler */
+
+	ret = devm_aperture_acquire_for_platform_device(pdev, par->base, par->size);
+	if (ret) {
+		dev_err(&pdev->dev, "Unable to acquire aperture: %d\n", ret);
+		goto error_genpds;
+	}
+	ret = register_framebuffer(info);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "Unable to register simplefb: %d\n", ret);
+		goto error_genpds;
+	}
+
+	dev_info(&pdev->dev, "fb%d: simplefb registered!\n", info->node);
+
+	return 0;
+
+error_genpds:
+	simplefb_detach_genpds(par);
+error_regulators:
+	simplefb_regulators_destroy(par);
+error_clocks:
+	simplefb_clocks_destroy(par);
+error_unmap:
+	iounmap(info->screen_base);
+error_fb_release:
+	framebuffer_release(info);
+error_release_mem_region:
+	if (mem != res)
+		release_mem_region(mem->start, resource_size(mem));
+	return ret;
+}
+
+static void simplefb_remove(struct platform_device *pdev)
+{
+	struct fb_info *info = platform_get_drvdata(pdev);
+
+	/* simplefb_destroy takes care of info cleanup */
+	unregister_framebuffer(info);
+}
+
+static const struct of_device_id simplefb_of_match[] = {
+	{ .compatible = "simple-framebuffer", },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, simplefb_of_match);
+
+static struct platform_driver simplefb_driver = {
+	.driver = {
+		.name = "simple-framebuffer",
+		.of_match_table = simplefb_of_match,
+	},
+	.probe = simplefb_probe,
+	.remove = simplefb_remove,
+};
+
+module_platform_driver(simplefb_driver);
+
+MODULE_AUTHOR("Stephen Warren <swarren@wwwdotorg.org>");
+MODULE_DESCRIPTION("Simple framebuffer driver");
+MODULE_LICENSE("GPL v2");