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, 151 insertions, 0 deletions

diff --git a/drivers/video/fbdev/q40fb.c b/drivers/video/fbdev/q40fb.c
new file mode 100644
index 000000000..1ff8fa176
--- /dev/null
+++ b/drivers/video/fbdev/q40fb.c
@@ -0,0 +1,151 @@
+/*
+ * linux/drivers/video/q40fb.c -- Q40 frame buffer device
+ *
+ * Copyright (C) 2001
+ *
+ *      Richard Zidlicky <rz@linux-m68k.org>
+ *
+ *  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.
+ */
+
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/string.h>
+#include <linux/mm.h>
+#include <linux/delay.h>
+#include <linux/interrupt.h>
+#include <linux/platform_device.h>
+
+#include <linux/uaccess.h>
+#include <asm/setup.h>
+#include <asm/q40_master.h>
+#include <linux/fb.h>
+#include <linux/module.h>
+
+#define Q40_PHYS_SCREEN_ADDR 0xFE800000
+
+static struct fb_fix_screeninfo q40fb_fix = {
+	.id		= "Q40",
+	.smem_len	= 1024*1024,
+	.type		= FB_TYPE_PACKED_PIXELS,
+	.visual		= FB_VISUAL_TRUECOLOR,
+	.line_length	= 1024*2,
+	.accel		= FB_ACCEL_NONE,
+};
+
+static const struct fb_var_screeninfo q40fb_var = {
+	.xres		= 1024,
+	.yres		= 512,
+	.xres_virtual	= 1024,
+	.yres_virtual	= 512,
+	.bits_per_pixel	= 16,
+    	.red		= {6, 5, 0},
+	.green		= {11, 5, 0},
+	.blue		= {0, 6, 0},
+	.activate	= FB_ACTIVATE_NOW,
+	.height		= 230,
+	.width		= 300,
+	.vmode		= FB_VMODE_NONINTERLACED,
+};
+
+static int q40fb_setcolreg(unsigned regno, unsigned red, unsigned green,
+			   unsigned blue, unsigned transp,
+			   struct fb_info *info)
+{
+    /*
+     *  Set a single color register. The values supplied have a 16 bit
+     *  magnitude.
+     *  Return != 0 for invalid regno.
+     */
+
+    if (regno > 255)
+	    return 1;
+    red>>=11;
+    green>>=11;
+    blue>>=10;
+
+    if (regno < 16) {
+	((u32 *)info->pseudo_palette)[regno] = ((red & 31) <<6) |
+					       ((green & 31) << 11) |
+					       (blue & 63);
+    }
+    return 0;
+}
+
+static const struct fb_ops q40fb_ops = {
+	.owner		= THIS_MODULE,
+	FB_DEFAULT_IOMEM_OPS,
+	.fb_setcolreg	= q40fb_setcolreg,
+};
+
+static int q40fb_probe(struct platform_device *dev)
+{
+	struct fb_info *info;
+
+	if (!MACH_IS_Q40)
+		return -ENXIO;
+
+	/* mapped in q40/config.c */
+	q40fb_fix.smem_start = Q40_PHYS_SCREEN_ADDR;
+
+	info = framebuffer_alloc(sizeof(u32) * 16, &dev->dev);
+	if (!info)
+		return -ENOMEM;
+
+	info->var = q40fb_var;
+	info->fix = q40fb_fix;
+	info->fbops = &q40fb_ops;
+	info->pseudo_palette = info->par;
+	info->par = NULL;
+	info->screen_base = (char *) q40fb_fix.smem_start;
+
+	if (fb_alloc_cmap(&info->cmap, 256, 0) < 0) {
+		framebuffer_release(info);
+		return -ENOMEM;
+	}
+
+	master_outb(3, DISPLAY_CONTROL_REG);
+
+	if (register_framebuffer(info) < 0) {
+		printk(KERN_ERR "Unable to register Q40 frame buffer\n");
+		fb_dealloc_cmap(&info->cmap);
+		framebuffer_release(info);
+		return -EINVAL;
+	}
+
+	fb_info(info, "Q40 frame buffer alive and kicking !\n");
+	return 0;
+}
+
+static struct platform_driver q40fb_driver = {
+	.probe	= q40fb_probe,
+	.driver	= {
+		.name	= "q40fb",
+	},
+};
+
+static struct platform_device q40fb_device = {
+	.name	= "q40fb",
+};
+
+static int __init q40fb_init(void)
+{
+	int ret = 0;
+
+	if (fb_get_options("q40fb", NULL))
+		return -ENODEV;
+
+	ret = platform_driver_register(&q40fb_driver);
+
+	if (!ret) {
+		ret = platform_device_register(&q40fb_device);
+		if (ret)
+			platform_driver_unregister(&q40fb_driver);
+	}
+	return ret;
+}
+
+module_init(q40fb_init);
+MODULE_LICENSE("GPL");