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, 135 insertions, 0 deletions

diff --git a/drivers/video/cmdline.c b/drivers/video/cmdline.c
new file mode 100644
index 000000000..49ee3fb49
--- /dev/null
+++ b/drivers/video/cmdline.c
@@ -0,0 +1,135 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Based on the fbdev code in drivers/video/fbdev/core/fb_cmdline:
+ *
+ *  Copyright (C) 2014 Intel Corp
+ *  Copyright (C) 1994 Martin Schaller
+ *
+ *	2001 - Documented with DocBook
+ *	- Brad Douglas <brad@neruo.com>
+ *
+ * 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.
+ *
+ * Authors:
+ *    Daniel Vetter <daniel.vetter@ffwll.ch>
+ */
+
+#include <linux/fb.h> /* for FB_MAX */
+#include <linux/init.h>
+
+#include <video/cmdline.h>
+
+/*
+ * FB_MAX is the maximum number of framebuffer devices and also
+ * the maximum number of video= parameters. Although not directly
+ * related to each other, it makes sense to keep it that way.
+ */
+static const char *video_options[FB_MAX] __read_mostly;
+static const char *video_option __read_mostly;
+static int video_of_only __read_mostly;
+
+static const char *__video_get_option_string(const char *name)
+{
+	const char *options = NULL;
+	size_t name_len = 0;
+
+	if (name)
+		name_len = strlen(name);
+
+	if (name_len) {
+		unsigned int i;
+		const char *opt;
+
+		for (i = 0; i < ARRAY_SIZE(video_options); ++i) {
+			if (!video_options[i])
+				continue;
+			if (video_options[i][0] == '\0')
+				continue;
+			opt = video_options[i];
+			if (!strncmp(opt, name, name_len) && opt[name_len] == ':')
+				options = opt + name_len + 1;
+		}
+	}
+
+	/* No match, return global options */
+	if (!options)
+		options = video_option;
+
+	return options;
+}
+
+/**
+ * video_get_options - get kernel boot parameters
+ * @name:	name of the output as it would appear in the boot parameter
+ *		line (video=<name>:<options>)
+ *
+ * Looks up the video= options for the given name. Names are connector
+ * names with DRM, or driver names with fbdev. If no video option for
+ * the name has been specified, the function returns the global video=
+ * setting. A @name of NULL always returns the global video setting.
+ *
+ * Returns:
+ * The string of video options for the given name, or NULL if no video
+ * option has been specified.
+ */
+const char *video_get_options(const char *name)
+{
+	return __video_get_option_string(name);
+}
+EXPORT_SYMBOL(video_get_options);
+
+#if IS_ENABLED(CONFIG_FB_CORE)
+bool __video_get_options(const char *name, const char **options, bool is_of)
+{
+	bool enabled = true;
+	const char *opt = NULL;
+
+	if (video_of_only && !is_of)
+		enabled = false;
+
+	opt = __video_get_option_string(name);
+
+	if (options)
+		*options = opt;
+
+	return enabled;
+}
+EXPORT_SYMBOL(__video_get_options);
+#endif
+
+/*
+ * Process command line options for video adapters. This function is
+ * a __setup and __init function. It only stores the options. Drivers
+ * have to call video_get_options() as necessary.
+ */
+static int __init video_setup(char *options)
+{
+	if (!options || !*options)
+		goto out;
+
+	if (!strncmp(options, "ofonly", 6)) {
+		video_of_only = true;
+		goto out;
+	}
+
+	if (strchr(options, ':')) {
+		/* named */
+		size_t i;
+
+		for (i = 0; i < ARRAY_SIZE(video_options); i++) {
+			if (!video_options[i]) {
+				video_options[i] = options;
+				break;
+			}
+		}
+	} else {
+		/* global */
+		video_option = options;
+	}
+
+out:
+	return 1;
+}
+__setup("video=", video_setup);