KVM: Don't pre-reserve xarray entries when storing empty/NULL attributesgrafted

Skip the xarray reservation loop when clearing all memory attributes, as
storing NULL only erases the entry and never needs to allocate, so no
reservation (and no cleanup of a failed one) is required in that case.

Suggested-by: Sean Christopherson <seanjc@google.com>
Cc: David Ballesteros <davimaba.v@proton.me>
Signed-off-by: Zeng Chi <zengchi@kylinos.cn>
Link: https://patch.msgid.link/20260921102442.1232375-1-zeng_chi911@163.com
[sean: split to separate patch]
Signed-off-by: Sean Christopherson <seanjc@google.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);