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, 95 insertions, 0 deletions

diff --git a/drivers/hid/hid-lg2ff.c b/drivers/hid/hid-lg2ff.c
new file mode 100644
index 000000000..c3e85b079
--- /dev/null
+++ b/drivers/hid/hid-lg2ff.c
@@ -0,0 +1,95 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  Force feedback support for Logitech RumblePad and Rumblepad 2
+ *
+ *  Copyright (c) 2008 Anssi Hannula <anssi.hannula@gmail.com>
+ */
+
+/*
+ */
+
+
+#include <linux/input.h>
+#include <linux/slab.h>
+#include <linux/hid.h>
+
+#include "hid-lg.h"
+
+struct lg2ff_device {
+	struct hid_report *report;
+};
+
+static int play_effect(struct input_dev *dev, void *data,
+			 struct ff_effect *effect)
+{
+	struct hid_device *hid = input_get_drvdata(dev);
+	struct lg2ff_device *lg2ff = data;
+	int weak, strong;
+
+	strong = effect->u.rumble.strong_magnitude;
+	weak = effect->u.rumble.weak_magnitude;
+
+	if (weak || strong) {
+		weak = weak * 0xff / 0xffff;
+		strong = strong * 0xff / 0xffff;
+
+		lg2ff->report->field[0]->value[0] = 0x51;
+		lg2ff->report->field[0]->value[2] = weak;
+		lg2ff->report->field[0]->value[4] = strong;
+	} else {
+		lg2ff->report->field[0]->value[0] = 0xf3;
+		lg2ff->report->field[0]->value[2] = 0x00;
+		lg2ff->report->field[0]->value[4] = 0x00;
+	}
+
+	hid_hw_request(hid, lg2ff->report, HID_REQ_SET_REPORT);
+	return 0;
+}
+
+int lg2ff_init(struct hid_device *hid)
+{
+	struct lg2ff_device *lg2ff;
+	struct hid_report *report;
+	struct hid_input *hidinput;
+	struct input_dev *dev;
+	int error;
+
+	if (list_empty(&hid->inputs)) {
+		hid_err(hid, "no inputs found\n");
+		return -ENODEV;
+	}
+	hidinput = list_entry(hid->inputs.next, struct hid_input, list);
+	dev = hidinput->input;
+
+	/* Check that the report looks ok */
+	report = hid_validate_values(hid, HID_OUTPUT_REPORT, 0, 0, 7);
+	if (!report)
+		return -ENODEV;
+
+	lg2ff = kmalloc_obj(struct lg2ff_device);
+	if (!lg2ff)
+		return -ENOMEM;
+
+	set_bit(FF_RUMBLE, dev->ffbit);
+
+	error = input_ff_create_memless(dev, lg2ff, play_effect);
+	if (error) {
+		kfree(lg2ff);
+		return error;
+	}
+
+	lg2ff->report = report;
+	report->field[0]->value[0] = 0xf3;
+	report->field[0]->value[1] = 0x00;
+	report->field[0]->value[2] = 0x00;
+	report->field[0]->value[3] = 0x00;
+	report->field[0]->value[4] = 0x00;
+	report->field[0]->value[5] = 0x00;
+	report->field[0]->value[6] = 0x00;
+
+	hid_hw_request(hid, report, HID_REQ_SET_REPORT);
+
+	hid_info(hid, "Force feedback for Logitech variant 2 rumble devices by Anssi Hannula <anssi.hannula@gmail.com>\n");
+
+	return 0;
+}