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, 322 insertions, 0 deletions

diff --git a/drivers/video/fbdev/goldfishfb.c b/drivers/video/fbdev/goldfishfb.c
new file mode 100644
index 000000000..e5d79886e
--- /dev/null
+++ b/drivers/video/fbdev/goldfishfb.c
@@ -0,0 +1,322 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2007 Google, Inc.
+ * Copyright (C) 2012 Intel, Inc.
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/dma-mapping.h>
+#include <linux/errno.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+#include <linux/delay.h>
+#include <linux/mm.h>
+#include <linux/fb.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/ioport.h>
+#include <linux/platform_device.h>
+#include <linux/acpi.h>
+
+enum {
+	FB_GET_WIDTH        = 0x00,
+	FB_GET_HEIGHT       = 0x04,
+	FB_INT_STATUS       = 0x08,
+	FB_INT_ENABLE       = 0x0c,
+	FB_SET_BASE         = 0x10,
+	FB_SET_ROTATION     = 0x14,
+	FB_SET_BLANK        = 0x18,
+	FB_GET_PHYS_WIDTH   = 0x1c,
+	FB_GET_PHYS_HEIGHT  = 0x20,
+
+	FB_INT_VSYNC             = 1U << 0,
+	FB_INT_BASE_UPDATE_DONE  = 1U << 1
+};
+
+struct goldfish_fb {
+	void __iomem *reg_base;
+	int irq;
+	spinlock_t lock;
+	wait_queue_head_t wait;
+	int base_update_count;
+	int rotation;
+	struct fb_info fb;
+	u32 cmap[16];
+};
+
+static irqreturn_t goldfish_fb_interrupt(int irq, void *dev_id)
+{
+	unsigned long irq_flags;
+	struct goldfish_fb *fb = dev_id;
+	u32 status;
+
+	spin_lock_irqsave(&fb->lock, irq_flags);
+	status = readl(fb->reg_base + FB_INT_STATUS);
+	if (status & FB_INT_BASE_UPDATE_DONE) {
+		fb->base_update_count++;
+		wake_up(&fb->wait);
+	}
+	spin_unlock_irqrestore(&fb->lock, irq_flags);
+	return status ? IRQ_HANDLED : IRQ_NONE;
+}
+
+static inline u32 convert_bitfield(int val, struct fb_bitfield *bf)
+{
+	unsigned int mask = (1 << bf->length) - 1;
+
+	return (val >> (16 - bf->length) & mask) << bf->offset;
+}
+
+static int
+goldfish_fb_setcolreg(unsigned int regno, unsigned int red, unsigned int green,
+		 unsigned int blue, unsigned int transp, struct fb_info *info)
+{
+	struct goldfish_fb *fb = container_of(info, struct goldfish_fb, fb);
+
+	if (regno < 16) {
+		fb->cmap[regno] = convert_bitfield(transp, &fb->fb.var.transp) |
+				  convert_bitfield(blue, &fb->fb.var.blue) |
+				  convert_bitfield(green, &fb->fb.var.green) |
+				  convert_bitfield(red, &fb->fb.var.red);
+		return 0;
+	} else {
+		return 1;
+	}
+}
+
+static int goldfish_fb_check_var(struct fb_var_screeninfo *var,
+							struct fb_info *info)
+{
+	if ((var->rotate & 1) != (info->var.rotate & 1)) {
+		if ((var->xres != info->var.yres) ||
+				(var->yres != info->var.xres) ||
+				(var->xres_virtual != info->var.yres) ||
+				(var->yres_virtual > info->var.xres * 2) ||
+				(var->yres_virtual < info->var.xres)) {
+			return -EINVAL;
+		}
+	} else {
+		if ((var->xres != info->var.xres) ||
+		   (var->yres != info->var.yres) ||
+		   (var->xres_virtual != info->var.xres) ||
+		   (var->yres_virtual > info->var.yres * 2) ||
+		   (var->yres_virtual < info->var.yres)) {
+			return -EINVAL;
+		}
+	}
+	if ((var->xoffset != info->var.xoffset) ||
+			(var->bits_per_pixel != info->var.bits_per_pixel) ||
+			(var->grayscale != info->var.grayscale)) {
+		return -EINVAL;
+	}
+	return 0;
+}
+
+static int goldfish_fb_set_par(struct fb_info *info)
+{
+	struct goldfish_fb *fb = container_of(info, struct goldfish_fb, fb);
+
+	if (fb->rotation != fb->fb.var.rotate) {
+		info->fix.line_length = info->var.xres * 2;
+		fb->rotation = fb->fb.var.rotate;
+		writel(fb->rotation, fb->reg_base + FB_SET_ROTATION);
+	}
+	return 0;
+}
+
+
+static int goldfish_fb_pan_display(struct fb_var_screeninfo *var,
+							struct fb_info *info)
+{
+	unsigned long irq_flags;
+	int base_update_count;
+	struct goldfish_fb *fb = container_of(info, struct goldfish_fb, fb);
+
+	spin_lock_irqsave(&fb->lock, irq_flags);
+	base_update_count = fb->base_update_count;
+	writel(fb->fb.fix.smem_start + fb->fb.var.xres * 2 * var->yoffset,
+						fb->reg_base + FB_SET_BASE);
+	spin_unlock_irqrestore(&fb->lock, irq_flags);
+	if (!wait_event_timeout(fb->wait,
+				fb->base_update_count != base_update_count,
+				HZ / 15)) {
+		pr_err("%s: timeout waiting for base update\n", __func__);
+		return -ETIMEDOUT;
+	}
+	return 0;
+}
+
+static int goldfish_fb_blank(int blank, struct fb_info *info)
+{
+	struct goldfish_fb *fb = container_of(info, struct goldfish_fb, fb);
+
+	switch (blank) {
+	case FB_BLANK_NORMAL:
+		writel(1, fb->reg_base + FB_SET_BLANK);
+		break;
+	case FB_BLANK_UNBLANK:
+		writel(0, fb->reg_base + FB_SET_BLANK);
+		break;
+	}
+	return 0;
+}
+
+static const struct fb_ops goldfish_fb_ops = {
+	.owner          = THIS_MODULE,
+	FB_DEFAULT_IOMEM_OPS,
+	.fb_check_var   = goldfish_fb_check_var,
+	.fb_set_par     = goldfish_fb_set_par,
+	.fb_setcolreg   = goldfish_fb_setcolreg,
+	.fb_pan_display = goldfish_fb_pan_display,
+	.fb_blank	= goldfish_fb_blank,
+};
+
+
+static int goldfish_fb_probe(struct platform_device *pdev)
+{
+	int ret;
+	struct goldfish_fb *fb;
+	size_t framesize;
+	u32 width, height;
+	dma_addr_t fbpaddr;
+
+	fb = kzalloc_obj(*fb);
+	if (fb == NULL) {
+		ret = -ENOMEM;
+		goto err_fb_alloc_failed;
+	}
+	spin_lock_init(&fb->lock);
+	init_waitqueue_head(&fb->wait);
+	platform_set_drvdata(pdev, fb);
+
+	fb->reg_base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(fb->reg_base)) {
+		ret = PTR_ERR(fb->reg_base);
+		goto err_no_io_base;
+	}
+
+	fb->irq = platform_get_irq(pdev, 0);
+	if (fb->irq < 0) {
+		ret = fb->irq;
+		goto err_no_irq;
+	}
+
+	width = readl(fb->reg_base + FB_GET_WIDTH);
+	height = readl(fb->reg_base + FB_GET_HEIGHT);
+
+	fb->fb.fbops		= &goldfish_fb_ops;
+	fb->fb.pseudo_palette	= fb->cmap;
+	fb->fb.fix.type		= FB_TYPE_PACKED_PIXELS;
+	fb->fb.fix.visual = FB_VISUAL_TRUECOLOR;
+	fb->fb.fix.line_length = width * 2;
+	fb->fb.fix.accel	= FB_ACCEL_NONE;
+	fb->fb.fix.ypanstep = 1;
+
+	fb->fb.var.xres		= width;
+	fb->fb.var.yres		= height;
+	fb->fb.var.xres_virtual	= width;
+	fb->fb.var.yres_virtual	= height * 2;
+	fb->fb.var.bits_per_pixel = 16;
+	fb->fb.var.activate	= FB_ACTIVATE_NOW;
+	fb->fb.var.height	= readl(fb->reg_base + FB_GET_PHYS_HEIGHT);
+	fb->fb.var.width	= readl(fb->reg_base + FB_GET_PHYS_WIDTH);
+	fb->fb.var.pixclock	= 0;
+
+	fb->fb.var.red.offset = 11;
+	fb->fb.var.red.length = 5;
+	fb->fb.var.green.offset = 5;
+	fb->fb.var.green.length = 6;
+	fb->fb.var.blue.offset = 0;
+	fb->fb.var.blue.length = 5;
+
+	framesize = width * height * 2 * 2;
+	fb->fb.screen_base = (char __force __iomem *)dma_alloc_coherent(
+						&pdev->dev, framesize,
+						&fbpaddr, GFP_KERNEL);
+	pr_debug("allocating frame buffer %d * %d, got %p\n",
+					width, height, fb->fb.screen_base);
+	if (fb->fb.screen_base == NULL) {
+		ret = -ENOMEM;
+		goto err_alloc_screen_base_failed;
+	}
+	fb->fb.fix.smem_start = fbpaddr;
+	fb->fb.fix.smem_len = framesize;
+
+	ret = fb_set_var(&fb->fb, &fb->fb.var);
+	if (ret)
+		goto err_fb_set_var_failed;
+
+	ret = request_irq(fb->irq, goldfish_fb_interrupt, IRQF_SHARED,
+							pdev->name, fb);
+	if (ret)
+		goto err_request_irq_failed;
+
+	writel(FB_INT_BASE_UPDATE_DONE, fb->reg_base + FB_INT_ENABLE);
+	ret = goldfish_fb_pan_display(&fb->fb.var, &fb->fb); /* updates base */
+	if (ret)
+		goto err_pan_display_failed;
+
+	ret = register_framebuffer(&fb->fb);
+	if (ret)
+		goto err_register_framebuffer_failed;
+	return 0;
+
+err_register_framebuffer_failed:
+err_pan_display_failed:
+	free_irq(fb->irq, fb);
+err_request_irq_failed:
+err_fb_set_var_failed:
+	dma_free_coherent(&pdev->dev, framesize,
+				(void *)fb->fb.screen_base,
+				fb->fb.fix.smem_start);
+err_alloc_screen_base_failed:
+err_no_irq:
+err_no_io_base:
+	kfree(fb);
+err_fb_alloc_failed:
+	return ret;
+}
+
+static void goldfish_fb_remove(struct platform_device *pdev)
+{
+	size_t framesize;
+	struct goldfish_fb *fb = platform_get_drvdata(pdev);
+
+	framesize = fb->fb.var.xres_virtual * fb->fb.var.yres_virtual * 2;
+	unregister_framebuffer(&fb->fb);
+	free_irq(fb->irq, fb);
+
+	dma_free_coherent(&pdev->dev, framesize, (void *)fb->fb.screen_base,
+						fb->fb.fix.smem_start);
+	kfree(fb);
+}
+
+static const struct of_device_id goldfish_fb_of_match[] = {
+	{ .compatible = "google,goldfish-fb", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, goldfish_fb_of_match);
+
+#ifdef CONFIG_ACPI
+static const struct acpi_device_id goldfish_fb_acpi_match[] = {
+	{ "GFSH0004", 0 },
+	{ },
+};
+MODULE_DEVICE_TABLE(acpi, goldfish_fb_acpi_match);
+#endif
+
+static struct platform_driver goldfish_fb_driver = {
+	.probe		= goldfish_fb_probe,
+	.remove		= goldfish_fb_remove,
+	.driver = {
+		.name = "goldfish_fb",
+		.of_match_table = goldfish_fb_of_match,
+		.acpi_match_table = ACPI_PTR(goldfish_fb_acpi_match),
+	}
+};
+
+module_platform_driver(goldfish_fb_driver);
+
+MODULE_DESCRIPTION("Goldfish Virtual Platform Framebuffer driver");
+MODULE_LICENSE("GPL v2");