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, 200 insertions, 0 deletions

diff --git a/drivers/input/touchscreen/mtouch.c b/drivers/input/touchscreen/mtouch.c
new file mode 100644
index 000000000..cc2d206d2
--- /dev/null
+++ b/drivers/input/touchscreen/mtouch.c
@@ -0,0 +1,200 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * MicroTouch (3M) serial touchscreen driver
+ *
+ * Copyright (c) 2004 Vojtech Pavlik
+ */
+
+
+/*
+ * 2005/02/19 Dan Streetman <ddstreet@ieee.org>
+ *   Copied elo.c and edited for MicroTouch protocol
+ */
+
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/input.h>
+#include <linux/serio.h>
+
+#define DRIVER_DESC	"MicroTouch serial touchscreen driver"
+
+MODULE_AUTHOR("Vojtech Pavlik <vojtech@ucw.cz>");
+MODULE_DESCRIPTION(DRIVER_DESC);
+MODULE_LICENSE("GPL");
+
+/*
+ * Definitions & global arrays.
+ */
+
+#define MTOUCH_FORMAT_TABLET_STATUS_BIT 0x80
+#define MTOUCH_FORMAT_TABLET_TOUCH_BIT 0x40
+#define MTOUCH_FORMAT_TABLET_LENGTH 5
+#define MTOUCH_RESPONSE_BEGIN_BYTE 0x01
+#define MTOUCH_RESPONSE_END_BYTE 0x0d
+
+/* todo: check specs for max length of all responses */
+#define MTOUCH_MAX_LENGTH 16
+
+#define MTOUCH_MIN_XC 0
+#define MTOUCH_MAX_XC 0x3fff
+#define MTOUCH_MIN_YC 0
+#define MTOUCH_MAX_YC 0x3fff
+
+#define MTOUCH_GET_XC(data) (((data[2])<<7) | data[1])
+#define MTOUCH_GET_YC(data) (((data[4])<<7) | data[3])
+#define MTOUCH_GET_TOUCHED(data) (MTOUCH_FORMAT_TABLET_TOUCH_BIT & data[0])
+
+/*
+ * Per-touchscreen data.
+ */
+
+struct mtouch {
+	struct input_dev *dev;
+	struct serio *serio;
+	int idx;
+	unsigned char data[MTOUCH_MAX_LENGTH];
+	char phys[32];
+};
+
+static void mtouch_process_format_tablet(struct mtouch *mtouch)
+{
+	struct input_dev *dev = mtouch->dev;
+
+	if (MTOUCH_FORMAT_TABLET_LENGTH == ++mtouch->idx) {
+		input_report_abs(dev, ABS_X, MTOUCH_GET_XC(mtouch->data));
+		input_report_abs(dev, ABS_Y, MTOUCH_MAX_YC - MTOUCH_GET_YC(mtouch->data));
+		input_report_key(dev, BTN_TOUCH, MTOUCH_GET_TOUCHED(mtouch->data));
+		input_sync(dev);
+
+		mtouch->idx = 0;
+	}
+}
+
+static void mtouch_process_response(struct mtouch *mtouch)
+{
+	if (MTOUCH_RESPONSE_END_BYTE == mtouch->data[mtouch->idx++]) {
+		/* FIXME - process response */
+		mtouch->idx = 0;
+	} else if (MTOUCH_MAX_LENGTH == mtouch->idx) {
+		printk(KERN_ERR "mtouch.c: too many response bytes\n");
+		mtouch->idx = 0;
+	}
+}
+
+static irqreturn_t mtouch_interrupt(struct serio *serio,
+		unsigned char data, unsigned int flags)
+{
+	struct mtouch *mtouch = serio_get_drvdata(serio);
+
+	mtouch->data[mtouch->idx] = data;
+
+	if (MTOUCH_FORMAT_TABLET_STATUS_BIT & mtouch->data[0])
+		mtouch_process_format_tablet(mtouch);
+	else if (MTOUCH_RESPONSE_BEGIN_BYTE == mtouch->data[0])
+		mtouch_process_response(mtouch);
+	else
+		printk(KERN_DEBUG "mtouch.c: unknown/unsynchronized data from device, byte %x\n",mtouch->data[0]);
+
+	return IRQ_HANDLED;
+}
+
+/*
+ * mtouch_disconnect() is the opposite of mtouch_connect()
+ */
+
+static void mtouch_disconnect(struct serio *serio)
+{
+	struct mtouch *mtouch = serio_get_drvdata(serio);
+
+	input_get_device(mtouch->dev);
+	input_unregister_device(mtouch->dev);
+	serio_close(serio);
+	serio_set_drvdata(serio, NULL);
+	input_put_device(mtouch->dev);
+	kfree(mtouch);
+}
+
+/*
+ * mtouch_connect() is the routine that is called when someone adds a
+ * new serio device that supports MicroTouch (Format Tablet) protocol and registers it as
+ * an input device.
+ */
+
+static int mtouch_connect(struct serio *serio, struct serio_driver *drv)
+{
+	struct mtouch *mtouch;
+	struct input_dev *input_dev;
+	int err;
+
+	mtouch = kzalloc_obj(*mtouch);
+	input_dev = input_allocate_device();
+	if (!mtouch || !input_dev) {
+		err = -ENOMEM;
+		goto fail1;
+	}
+
+	mtouch->serio = serio;
+	mtouch->dev = input_dev;
+	scnprintf(mtouch->phys, sizeof(mtouch->phys), "%s/input0", serio->phys);
+
+	input_dev->name = "MicroTouch Serial TouchScreen";
+	input_dev->phys = mtouch->phys;
+	input_dev->id.bustype = BUS_RS232;
+	input_dev->id.vendor = SERIO_MICROTOUCH;
+	input_dev->id.product = 0;
+	input_dev->id.version = 0x0100;
+	input_dev->dev.parent = &serio->dev;
+	input_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS);
+	input_dev->keybit[BIT_WORD(BTN_TOUCH)] = BIT_MASK(BTN_TOUCH);
+	input_set_abs_params(mtouch->dev, ABS_X, MTOUCH_MIN_XC, MTOUCH_MAX_XC, 0, 0);
+	input_set_abs_params(mtouch->dev, ABS_Y, MTOUCH_MIN_YC, MTOUCH_MAX_YC, 0, 0);
+
+	serio_set_drvdata(serio, mtouch);
+
+	err = serio_open(serio, drv);
+	if (err)
+		goto fail2;
+
+	err = input_register_device(mtouch->dev);
+	if (err)
+		goto fail3;
+
+	return 0;
+
+ fail3:	serio_close(serio);
+ fail2:	serio_set_drvdata(serio, NULL);
+ fail1:	input_free_device(input_dev);
+	kfree(mtouch);
+	return err;
+}
+
+/*
+ * The serio driver structure.
+ */
+
+static const struct serio_device_id mtouch_serio_ids[] = {
+	{
+		.type	= SERIO_RS232,
+		.proto	= SERIO_MICROTOUCH,
+		.id	= SERIO_ANY,
+		.extra	= SERIO_ANY,
+	},
+	{ 0 }
+};
+
+MODULE_DEVICE_TABLE(serio, mtouch_serio_ids);
+
+static struct serio_driver mtouch_drv = {
+	.driver		= {
+		.name	= "mtouch",
+	},
+	.description	= DRIVER_DESC,
+	.id_table	= mtouch_serio_ids,
+	.interrupt	= mtouch_interrupt,
+	.connect	= mtouch_connect,
+	.disconnect	= mtouch_disconnect,
+};
+
+module_serio_driver(mtouch_drv);