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, 105 insertions, 0 deletions

diff --git a/include/video/display_timing.h b/include/video/display_timing.h
new file mode 100644
index 000000000..37a017607
--- /dev/null
+++ b/include/video/display_timing.h
@@ -0,0 +1,105 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright 2012 Steffen Trumtrar <s.trumtrar@pengutronix.de>
+ *
+ * description of display timings
+ */
+
+#ifndef __LINUX_DISPLAY_TIMING_H
+#define __LINUX_DISPLAY_TIMING_H
+
+#include <linux/bitops.h>
+#include <linux/types.h>
+
+enum display_flags {
+	DISPLAY_FLAGS_HSYNC_LOW		= BIT(0),
+	DISPLAY_FLAGS_HSYNC_HIGH	= BIT(1),
+	DISPLAY_FLAGS_VSYNC_LOW		= BIT(2),
+	DISPLAY_FLAGS_VSYNC_HIGH	= BIT(3),
+
+	/* data enable flag */
+	DISPLAY_FLAGS_DE_LOW		= BIT(4),
+	DISPLAY_FLAGS_DE_HIGH		= BIT(5),
+	/* drive data on pos. edge */
+	DISPLAY_FLAGS_PIXDATA_POSEDGE	= BIT(6),
+	/* drive data on neg. edge */
+	DISPLAY_FLAGS_PIXDATA_NEGEDGE	= BIT(7),
+	DISPLAY_FLAGS_INTERLACED	= BIT(8),
+	DISPLAY_FLAGS_DOUBLESCAN	= BIT(9),
+	DISPLAY_FLAGS_DOUBLECLK		= BIT(10),
+	/* drive sync on pos. edge */
+	DISPLAY_FLAGS_SYNC_POSEDGE	= BIT(11),
+	/* drive sync on neg. edge */
+	DISPLAY_FLAGS_SYNC_NEGEDGE	= BIT(12),
+};
+
+/*
+ * A single signal can be specified via a range of minimal and maximal values
+ * with a typical value, that lies somewhere inbetween.
+ */
+struct timing_entry {
+	u32 min;
+	u32 typ;
+	u32 max;
+};
+
+/*
+ * Single "mode" entry. This describes one set of signal timings a display can
+ * have in one setting. This struct can later be converted to struct videomode
+ * (see include/video/videomode.h). As each timing_entry can be defined as a
+ * range, one struct display_timing may become multiple struct videomodes.
+ *
+ * Example: hsync active high, vsync active low
+ *
+ *				    Active Video
+ * Video  ______________________XXXXXXXXXXXXXXXXXXXXXX_____________________
+ *	  |<- sync ->|<- back ->|<----- active ----->|<- front ->|<- sync..
+ *	  |	     |	 porch  |		     |	 porch	 |
+ *
+ * HSync _|¯¯¯¯¯¯¯¯¯¯|___________________________________________|¯¯¯¯¯¯¯¯¯
+ *
+ * VSync ¯|__________|¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯|_________
+ */
+struct display_timing {
+	struct timing_entry pixelclock;
+
+	struct timing_entry hactive;		/* hor. active video */
+	struct timing_entry hfront_porch;	/* hor. front porch */
+	struct timing_entry hback_porch;	/* hor. back porch */
+	struct timing_entry hsync_len;		/* hor. sync len */
+
+	struct timing_entry vactive;		/* ver. active video */
+	struct timing_entry vfront_porch;	/* ver. front porch */
+	struct timing_entry vback_porch;	/* ver. back porch */
+	struct timing_entry vsync_len;		/* ver. sync len */
+
+	enum display_flags flags;		/* display flags */
+};
+
+/*
+ * This describes all timing settings a display provides.
+ * The native_mode is the default setting for this display.
+ * Drivers that can handle multiple videomodes should work with this struct and
+ * convert each entry to the desired end result.
+ */
+struct display_timings {
+	unsigned int num_timings;
+	unsigned int native_mode;
+
+	struct display_timing **timings;
+};
+
+/* get one entry from struct display_timings */
+static inline struct display_timing *display_timings_get(const struct
+							 display_timings *disp,
+							 unsigned int index)
+{
+	if (disp->num_timings > index)
+		return disp->timings[index];
+	else
+		return NULL;
+}
+
+void display_timings_release(struct display_timings *disp);
+
+#endif