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, 197 insertions, 0 deletions

diff --git a/drivers/video/fbdev/sunxvr1000.c b/drivers/video/fbdev/sunxvr1000.c
new file mode 100644
index 000000000..a93b06614
--- /dev/null
+++ b/drivers/video/fbdev/sunxvr1000.c
@@ -0,0 +1,197 @@
+/* sunxvr1000.c: Sun XVR-1000 fb driver for sparc64 systems
+ *
+ * License: GPL
+ *
+ * Copyright (C) 2010 David S. Miller (davem@davemloft.net)
+ */
+
+#include <linux/kernel.h>
+#include <linux/fb.h>
+#include <linux/init.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+
+struct gfb_info {
+	struct fb_info		*info;
+
+	char __iomem		*fb_base;
+	unsigned long		fb_base_phys;
+
+	struct device_node	*of_node;
+
+	unsigned int		width;
+	unsigned int		height;
+	unsigned int		depth;
+	unsigned int		fb_size;
+
+	u32			pseudo_palette[16];
+};
+
+static int gfb_get_props(struct gfb_info *gp)
+{
+	gp->width = of_getintprop_default(gp->of_node, "width", 0);
+	gp->height = of_getintprop_default(gp->of_node, "height", 0);
+	gp->depth = of_getintprop_default(gp->of_node, "depth", 32);
+
+	if (!gp->width || !gp->height) {
+		printk(KERN_ERR "gfb: Critical properties missing for %pOF\n",
+		       gp->of_node);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static int gfb_setcolreg(unsigned regno,
+			 unsigned red, unsigned green, unsigned blue,
+			 unsigned transp, struct fb_info *info)
+{
+	u32 value;
+
+	if (regno < 16) {
+		red >>= 8;
+		green >>= 8;
+		blue >>= 8;
+
+		value = (blue << 16) | (green << 8) | red;
+		((u32 *)info->pseudo_palette)[regno] = value;
+	}
+
+	return 0;
+}
+
+static const struct fb_ops gfb_ops = {
+	.owner			= THIS_MODULE,
+	FB_DEFAULT_IOMEM_OPS,
+	.fb_setcolreg		= gfb_setcolreg,
+};
+
+static int gfb_set_fbinfo(struct gfb_info *gp)
+{
+	struct fb_info *info = gp->info;
+	struct fb_var_screeninfo *var = &info->var;
+
+	info->fbops = &gfb_ops;
+	info->screen_base = gp->fb_base;
+	info->screen_size = gp->fb_size;
+
+	info->pseudo_palette = gp->pseudo_palette;
+
+	/* Fill fix common fields */
+	strscpy(info->fix.id, "gfb", sizeof(info->fix.id));
+        info->fix.smem_start = gp->fb_base_phys;
+        info->fix.smem_len = gp->fb_size;
+        info->fix.type = FB_TYPE_PACKED_PIXELS;
+	if (gp->depth == 32 || gp->depth == 24)
+		info->fix.visual = FB_VISUAL_TRUECOLOR;
+	else
+		info->fix.visual = FB_VISUAL_PSEUDOCOLOR;
+
+	var->xres = gp->width;
+	var->yres = gp->height;
+	var->xres_virtual = var->xres;
+	var->yres_virtual = var->yres;
+	var->bits_per_pixel = gp->depth;
+
+	var->red.offset = 0;
+	var->red.length = 8;
+	var->green.offset = 8;
+	var->green.length = 8;
+	var->blue.offset = 16;
+	var->blue.length = 8;
+	var->transp.offset = 0;
+	var->transp.length = 0;
+
+	if (fb_alloc_cmap(&info->cmap, 256, 0)) {
+		printk(KERN_ERR "gfb: Cannot allocate color map.\n");
+		return -ENOMEM;
+	}
+
+        return 0;
+}
+
+static int gfb_probe(struct platform_device *op)
+{
+	struct device_node *dp = op->dev.of_node;
+	struct fb_info *info;
+	struct gfb_info *gp;
+	int err;
+
+	info = framebuffer_alloc(sizeof(struct gfb_info), &op->dev);
+	if (!info) {
+		err = -ENOMEM;
+		goto err_out;
+	}
+
+	gp = info->par;
+	gp->info = info;
+	gp->of_node = dp;
+
+	gp->fb_base_phys = op->resource[6].start;
+
+	err = gfb_get_props(gp);
+	if (err)
+		goto err_release_fb;
+
+	/* Framebuffer length is the same regardless of resolution. */
+	info->fix.line_length = 16384;
+	gp->fb_size = info->fix.line_length * gp->height;
+
+	gp->fb_base = of_ioremap(&op->resource[6], 0,
+				 gp->fb_size, "gfb fb");
+	if (!gp->fb_base) {
+		err = -ENOMEM;
+		goto err_release_fb;
+	}
+
+	err = gfb_set_fbinfo(gp);
+	if (err)
+		goto err_unmap_fb;
+
+	printk("gfb: Found device at %pOF\n", dp);
+
+	err = register_framebuffer(info);
+	if (err < 0) {
+		printk(KERN_ERR "gfb: Could not register framebuffer %pOF\n",
+		       dp);
+		goto err_unmap_fb;
+	}
+
+	dev_set_drvdata(&op->dev, info);
+
+	return 0;
+
+err_unmap_fb:
+	of_iounmap(&op->resource[6], gp->fb_base, gp->fb_size);
+
+err_release_fb:
+        framebuffer_release(info);
+
+err_out:
+	return err;
+}
+
+static const struct of_device_id gfb_match[] = {
+	{
+		.name = "SUNW,gfb",
+	},
+	{},
+};
+
+static struct platform_driver gfb_driver = {
+	.probe		= gfb_probe,
+	.driver = {
+		.name			= "gfb",
+		.of_match_table		= gfb_match,
+		.suppress_bind_attrs	= true,
+	},
+};
+
+static int __init gfb_init(void)
+{
+	if (fb_get_options("gfb", NULL))
+		return -ENODEV;
+
+	return platform_driver_register(&gfb_driver);
+}
+device_initcall(gfb_init);