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, 301 insertions, 0 deletions

diff --git a/drivers/video/fbdev/pmag-aa-fb.c b/drivers/video/fbdev/pmag-aa-fb.c
new file mode 100644
index 000000000..acfc8c70c
--- /dev/null
+++ b/drivers/video/fbdev/pmag-aa-fb.c
@@ -0,0 +1,301 @@
+/*
+ *	linux/drivers/video/pmag-aa-fb.c
+ *	Copyright 2002 Karsten Merker <merker@debian.org>
+ *
+ *	PMAG-AA TurboChannel framebuffer card support ... derived from
+ *	pmag-ba-fb.c, which is Copyright (C) 1999, 2000, 2001 by
+ *	Michael Engel <engel@unix-ag.org>, Karsten Merker <merker@debian.org>
+ *	and Harald Koerfgen <hkoerfg@web.de>, which itself is derived from
+ *	"HP300 Topcat framebuffer support (derived from macfb of all things)
+ *	Phil Blundell <philb@gnu.org> 1998"
+ *	Copyright (c) 2016  Maciej W. Rozycki
+ *
+ *	This file is subject to the terms and conditions of the GNU General
+ *	Public License.  See the file COPYING in the main directory of this
+ *	archive for more details.
+ *
+ *	2002-09-28  Karsten Merker <merker@linuxtag.org>
+ *		Version 0.01: First try to get a PMAG-AA running.
+ *
+ *	2003-02-24  Thiemo Seufer  <seufer@csv.ica.uni-stuttgart.de>
+ *		Version 0.02: Major code cleanup.
+ *
+ *	2003-09-21  Thiemo Seufer  <seufer@csv.ica.uni-stuttgart.de>
+ *		Hardware cursor support.
+ *
+ *	2016-02-21  Maciej W. Rozycki  <macro@linux-mips.org>
+ *		Version 0.03: Rewritten for the new FB and TC APIs.
+ */
+
+#include <linux/compiler.h>
+#include <linux/errno.h>
+#include <linux/fb.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/tc.h>
+#include <linux/timer.h>
+
+#include "bt455.h"
+#include "bt431.h"
+
+/* Version information */
+#define DRIVER_VERSION "0.03"
+#define DRIVER_AUTHOR "Karsten Merker <merker@linuxtag.org>"
+#define DRIVER_DESCRIPTION "PMAG-AA Framebuffer Driver"
+
+/*
+ * Bt455 RAM DAC register base offset (rel. to TC slot base address).
+ */
+#define PMAG_AA_BT455_OFFSET		0x100000
+
+/*
+ * Bt431 cursor generator offset (rel. to TC slot base address).
+ */
+#define PMAG_AA_BT431_OFFSET		0x180000
+
+/*
+ * Begin of PMAG-AA framebuffer memory relative to TC slot address,
+ * resolution is 1280x1024x1 (8 bits deep, but only LSB is used).
+ */
+#define PMAG_AA_ONBOARD_FBMEM_OFFSET	0x200000
+
+struct aafb_par {
+	void __iomem *mmio;
+	struct bt455_regs __iomem *bt455;
+	struct bt431_regs __iomem *bt431;
+};
+
+static const struct fb_var_screeninfo aafb_defined = {
+	.xres		= 1280,
+	.yres		= 1024,
+	.xres_virtual	= 2048,
+	.yres_virtual	= 1024,
+	.bits_per_pixel	= 8,
+	.grayscale	= 1,
+	.red.length	= 0,
+	.green.length	= 1,
+	.blue.length	= 0,
+	.activate	= FB_ACTIVATE_NOW,
+	.accel_flags	= FB_ACCEL_NONE,
+	.pixclock	= 7645,
+	.left_margin	= 224,
+	.right_margin	= 32,
+	.upper_margin	= 33,
+	.lower_margin	= 3,
+	.hsync_len	= 160,
+	.vsync_len	= 3,
+	.sync		= FB_SYNC_ON_GREEN,
+	.vmode		= FB_VMODE_NONINTERLACED,
+};
+
+static const struct fb_fix_screeninfo aafb_fix = {
+	.id		= "PMAG-AA",
+	.smem_len	= (2048 * 1024),
+	.type		= FB_TYPE_PACKED_PIXELS,
+	.visual		= FB_VISUAL_MONO10,
+	.ypanstep	= 1,
+	.ywrapstep	= 1,
+	.line_length	= 2048,
+	.mmio_len	= PMAG_AA_ONBOARD_FBMEM_OFFSET - PMAG_AA_BT455_OFFSET,
+};
+
+static int aafb_cursor(struct fb_info *info, struct fb_cursor *cursor)
+{
+	struct aafb_par *par = info->par;
+
+	if (cursor->image.height > BT431_CURSOR_SIZE ||
+	    cursor->image.width > BT431_CURSOR_SIZE) {
+		bt431_erase_cursor(par->bt431);
+		return -EINVAL;
+	}
+
+	if (!cursor->enable)
+		bt431_erase_cursor(par->bt431);
+
+	if (cursor->set & FB_CUR_SETPOS)
+		bt431_position_cursor(par->bt431,
+				      cursor->image.dx, cursor->image.dy);
+	if (cursor->set & FB_CUR_SETCMAP) {
+		u8 fg = cursor->image.fg_color ? 0xf : 0x0;
+		u8 bg = cursor->image.bg_color ? 0xf : 0x0;
+
+		bt455_write_cmap_entry(par->bt455, 8, bg);
+		bt455_write_cmap_next(par->bt455, bg);
+		bt455_write_ovly_next(par->bt455, fg);
+	}
+	if (cursor->set & (FB_CUR_SETSIZE | FB_CUR_SETSHAPE | FB_CUR_SETIMAGE))
+		bt431_set_cursor(par->bt431,
+				 cursor->image.data, cursor->mask, cursor->rop,
+				 cursor->image.width, cursor->image.height);
+
+	if (cursor->enable)
+		bt431_enable_cursor(par->bt431);
+
+	return 0;
+}
+
+/* 0 unblanks, any other blanks. */
+
+static int aafb_blank(int blank, struct fb_info *info)
+{
+	struct aafb_par *par = info->par;
+	u8 val = blank ? 0x00 : 0x0f;
+
+	bt455_write_cmap_entry(par->bt455, 1, val);
+	return 0;
+}
+
+static const struct fb_ops aafb_ops = {
+	.owner		= THIS_MODULE,
+	FB_DEFAULT_IOMEM_OPS,
+	.fb_blank	= aafb_blank,
+	.fb_cursor	= aafb_cursor,
+};
+
+static int pmagaafb_probe(struct device *dev)
+{
+	struct tc_dev *tdev = to_tc_dev(dev);
+	resource_size_t start, len;
+	struct fb_info *info;
+	struct aafb_par *par;
+	int err;
+
+	info = framebuffer_alloc(sizeof(struct aafb_par), dev);
+	if (!info)
+		return -ENOMEM;
+
+	par = info->par;
+	dev_set_drvdata(dev, info);
+
+	info->fbops = &aafb_ops;
+	info->fix = aafb_fix;
+	info->var = aafb_defined;
+
+	/* Request the I/O MEM resource. */
+	start = tdev->resource.start;
+	len = tdev->resource.end - start + 1;
+	if (!request_mem_region(start, len, dev_name(dev))) {
+		printk(KERN_ERR "%s: Cannot reserve FB region\n",
+		       dev_name(dev));
+		err = -EBUSY;
+		goto err_alloc;
+	}
+
+	/* MMIO mapping setup. */
+	info->fix.mmio_start = start + PMAG_AA_BT455_OFFSET;
+	par->mmio = ioremap(info->fix.mmio_start, info->fix.mmio_len);
+	if (!par->mmio) {
+		printk(KERN_ERR "%s: Cannot map MMIO\n", dev_name(dev));
+		err = -ENOMEM;
+		goto err_resource;
+	}
+	par->bt455 = par->mmio - PMAG_AA_BT455_OFFSET + PMAG_AA_BT455_OFFSET;
+	par->bt431 = par->mmio - PMAG_AA_BT455_OFFSET + PMAG_AA_BT431_OFFSET;
+
+	/* Frame buffer mapping setup. */
+	info->fix.smem_start = start + PMAG_AA_ONBOARD_FBMEM_OFFSET;
+	info->screen_base = ioremap(info->fix.smem_start,
+					    info->fix.smem_len);
+	if (!info->screen_base) {
+		printk(KERN_ERR "%s: Cannot map FB\n", dev_name(dev));
+		err = -ENOMEM;
+		goto err_mmio_map;
+	}
+	info->screen_size = info->fix.smem_len;
+
+	/* Init colormap. */
+	bt455_write_cmap_entry(par->bt455, 0, 0x0);
+	bt455_write_cmap_next(par->bt455, 0xf);
+
+	/* Init hardware cursor. */
+	bt431_erase_cursor(par->bt431);
+	bt431_init_cursor(par->bt431);
+
+	err = register_framebuffer(info);
+	if (err < 0) {
+		printk(KERN_ERR "%s: Cannot register framebuffer\n",
+		       dev_name(dev));
+		goto err_smem_map;
+	}
+
+	get_device(dev);
+
+	pr_info("fb%d: %s frame buffer device at %s\n",
+		info->node, info->fix.id, dev_name(dev));
+
+	return 0;
+
+
+err_smem_map:
+	iounmap(info->screen_base);
+
+err_mmio_map:
+	iounmap(par->mmio);
+
+err_resource:
+	release_mem_region(start, len);
+
+err_alloc:
+	framebuffer_release(info);
+	return err;
+}
+
+static int pmagaafb_remove(struct device *dev)
+{
+	struct tc_dev *tdev = to_tc_dev(dev);
+	struct fb_info *info = dev_get_drvdata(dev);
+	struct aafb_par *par = info->par;
+	resource_size_t start, len;
+
+	put_device(dev);
+	unregister_framebuffer(info);
+	iounmap(info->screen_base);
+	iounmap(par->mmio);
+	start = tdev->resource.start;
+	len = tdev->resource.end - start + 1;
+	release_mem_region(start, len);
+	framebuffer_release(info);
+	return 0;
+}
+
+/*
+ * Initialise the framebuffer.
+ */
+static const struct tc_device_id pmagaafb_tc_table[] = {
+	{ "DEC     ", "PMAG-AA " },
+	{ }
+};
+MODULE_DEVICE_TABLE(tc, pmagaafb_tc_table);
+
+static struct tc_driver pmagaafb_driver = {
+	.id_table	= pmagaafb_tc_table,
+	.driver		= {
+		.name	= "pmagaafb",
+		.bus	= &tc_bus_type,
+		.probe	= pmagaafb_probe,
+		.remove	= pmagaafb_remove,
+	},
+};
+
+static int __init pmagaafb_init(void)
+{
+#ifndef MODULE
+	if (fb_get_options("pmagaafb", NULL))
+		return -ENXIO;
+#endif
+	return tc_register_driver(&pmagaafb_driver);
+}
+
+static void __exit pmagaafb_exit(void)
+{
+	tc_unregister_driver(&pmagaafb_driver);
+}
+
+module_init(pmagaafb_init);
+module_exit(pmagaafb_exit);
+
+MODULE_AUTHOR(DRIVER_AUTHOR);
+MODULE_DESCRIPTION(DRIVER_DESCRIPTION);
+MODULE_LICENSE("GPL");