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, 177 insertions, 0 deletions

diff --git a/drivers/hid/hid-axff.c b/drivers/hid/hid-axff.c
new file mode 100644
index 000000000..2f4644708
--- /dev/null
+++ b/drivers/hid/hid-axff.c
@@ -0,0 +1,177 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Force feedback support for ACRUX game controllers
+ *
+ * From what I have gathered, these devices are mass produced in China
+ * by several vendors. They often share the same design as the original
+ * Xbox 360 controller.
+ *
+ * 1a34:0802 "ACRUX USB GAMEPAD 8116"
+ *  - tested with an EXEQ EQ-PCU-02090 game controller.
+ *
+ * Copyright (c) 2010 Sergei Kolzun <x0r@dv-life.ru>
+ */
+
+/*
+ */
+
+#include <linux/input.h>
+#include <linux/slab.h>
+#include <linux/hid.h>
+#include <linux/module.h>
+
+#include "hid-ids.h"
+
+#ifdef CONFIG_HID_ACRUX_FF
+
+struct axff_device {
+	struct hid_report *report;
+};
+
+static int axff_play(struct input_dev *dev, void *data, struct ff_effect *effect)
+{
+	struct hid_device *hid = input_get_drvdata(dev);
+	struct axff_device *axff = data;
+	struct hid_report *report = axff->report;
+	int field_count = 0;
+	int left, right;
+	int i, j;
+
+	left = effect->u.rumble.strong_magnitude;
+	right = effect->u.rumble.weak_magnitude;
+
+	dbg_hid("called with 0x%04x 0x%04x", left, right);
+
+	left = left * 0xff / 0xffff;
+	right = right * 0xff / 0xffff;
+
+	for (i = 0; i < report->maxfield; i++) {
+		for (j = 0; j < report->field[i]->report_count; j++) {
+			report->field[i]->value[j] =
+				field_count % 2 ? right : left;
+			field_count++;
+		}
+	}
+
+	dbg_hid("running with 0x%02x 0x%02x", left, right);
+	hid_hw_request(hid, axff->report, HID_REQ_SET_REPORT);
+
+	return 0;
+}
+
+static int ax_input_configured(struct hid_device *hid, struct hid_input *hidinput)
+{
+	struct axff_device *axff;
+	struct hid_report *report;
+	struct list_head *report_list = &hid->report_enum[HID_OUTPUT_REPORT].report_list;
+	struct input_dev *dev = hidinput->input;
+	int field_count = 0;
+	int i, j;
+	int error;
+
+	if (!list_is_first(&hidinput->list, &hid->inputs))
+		return 0;
+
+	report = list_first_entry_or_null(report_list, struct hid_report, list);
+	if (!report) {
+		hid_err(hid, "no output reports found\n");
+		return -ENODEV;
+	}
+	for (i = 0; i < report->maxfield; i++) {
+		for (j = 0; j < report->field[i]->report_count; j++) {
+			report->field[i]->value[j] = 0x00;
+			field_count++;
+		}
+	}
+
+	if (field_count < 4 && hid->product != 0xf705) {
+		hid_err(hid, "not enough fields in the report: %d\n",
+			field_count);
+		return -ENODEV;
+	}
+
+	axff = kzalloc_obj(struct axff_device);
+	if (!axff)
+		return -ENOMEM;
+
+	axff->report = report;
+	set_bit(FF_RUMBLE, dev->ffbit);
+
+	error = input_ff_create_memless(dev, axff, axff_play);
+	if (error)
+		goto err_free_mem;
+
+	hid_hw_request(hid, axff->report, HID_REQ_SET_REPORT);
+
+	hid_info(hid, "Force Feedback for ACRUX game controllers by Sergei Kolzun <x0r@dv-life.ru>\n");
+
+	return 0;
+
+err_free_mem:
+	kfree(axff);
+	return error;
+}
+#else
+static inline int ax_input_configured(struct hid_device *hid,
+				      struct hid_input *hidinput)
+{
+	return 0;
+}
+#endif
+
+static int ax_probe(struct hid_device *hdev, const struct hid_device_id *id)
+{
+	int error;
+
+	dev_dbg(&hdev->dev, "ACRUX HID hardware probe...\n");
+
+	error = hid_parse(hdev);
+	if (error) {
+		hid_err(hdev, "parse failed\n");
+		return error;
+	}
+
+	error = hid_hw_start(hdev, HID_CONNECT_DEFAULT);
+	if (error) {
+		hid_err(hdev, "hw start failed\n");
+		return error;
+	}
+	/*
+	 * We need to start polling device right away, otherwise
+	 * it will go into a coma.
+	 */
+	error = hid_hw_open(hdev);
+	if (error) {
+		dev_err(&hdev->dev, "hw open failed\n");
+		hid_hw_stop(hdev);
+		return error;
+	}
+
+	return 0;
+}
+
+static void ax_remove(struct hid_device *hdev)
+{
+	hid_hw_close(hdev);
+	hid_hw_stop(hdev);
+}
+
+static const struct hid_device_id ax_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_ACRUX, 0x0802), },
+	{ HID_USB_DEVICE(USB_VENDOR_ID_ACRUX, 0xf705), },
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, ax_devices);
+
+static struct hid_driver ax_driver = {
+	.name		= "acrux",
+	.id_table	= ax_devices,
+	.probe		= ax_probe,
+	.remove		= ax_remove,
+	.input_configured = ax_input_configured,
+};
+module_hid_driver(ax_driver);
+
+MODULE_AUTHOR("Sergei Kolzun");
+MODULE_DESCRIPTION("Force feedback support for ACRUX game controllers");
+MODULE_LICENSE("GPL");