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, 133 insertions, 0 deletions

diff --git a/drivers/hid/hid-google-stadiaff.c b/drivers/hid/hid-google-stadiaff.c
new file mode 100644
index 000000000..0214aae6b
--- /dev/null
+++ b/drivers/hid/hid-google-stadiaff.c
@@ -0,0 +1,133 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Stadia controller rumble support.
+ *
+ * Copyright 2023 Google LLC
+ */
+
+#include <linux/hid.h>
+#include <linux/input.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+
+#include "hid-ids.h"
+
+#define STADIA_FF_REPORT_ID 5
+
+struct stadiaff_device {
+	struct hid_device *hid;
+	struct hid_report *report;
+	u32 magnitudes;
+	struct work_struct work;
+};
+
+static void stadiaff_work(struct work_struct *work)
+{
+	struct stadiaff_device *stadiaff =
+		container_of(work, struct stadiaff_device, work);
+	struct hid_field *rumble_field = stadiaff->report->field[0];
+	u32 mags = READ_ONCE(stadiaff->magnitudes);
+
+	rumble_field->value[0] = mags & 0xffff;
+	rumble_field->value[1] = (mags >> 16) & 0xffff;
+
+	hid_hw_request(stadiaff->hid, stadiaff->report, HID_REQ_SET_REPORT);
+}
+
+static int stadiaff_play(struct input_dev *dev, void *data,
+			 struct ff_effect *effect)
+{
+	struct hid_device *hid = input_get_drvdata(dev);
+	struct stadiaff_device *stadiaff = hid_get_drvdata(hid);
+	u32 mags = (u32)effect->u.rumble.strong_magnitude |
+		  ((u32)effect->u.rumble.weak_magnitude << 16);
+
+	WRITE_ONCE(stadiaff->magnitudes, mags);
+	schedule_work(&stadiaff->work);
+
+	return 0;
+}
+
+static int stadia_input_open(struct input_dev *dev)
+{
+	struct hid_device *hid = input_get_drvdata(dev);
+	struct stadiaff_device *stadiaff = hid_get_drvdata(hid);
+	int error;
+
+	error = hid_hw_open(hid);
+	if (error)
+		return error;
+
+	enable_work(&stadiaff->work);
+	return 0;
+}
+
+static void stadia_input_close(struct input_dev *dev)
+{
+	struct hid_device *hid = input_get_drvdata(dev);
+	struct stadiaff_device *stadiaff = hid_get_drvdata(hid);
+
+	WRITE_ONCE(stadiaff->magnitudes, 0);
+	stadiaff_work(&stadiaff->work);
+	disable_work_sync(&stadiaff->work);
+
+	hid_hw_close(hid);
+}
+
+static int stadia_input_configured(struct hid_device *hid, struct hid_input *hidinput)
+{
+	struct stadiaff_device *stadiaff;
+	struct hid_report *report;
+	struct input_dev *dev = hidinput->input;
+	int error;
+
+	if (!list_is_first(&hidinput->list, &hid->inputs))
+		return 0;
+
+	report = hid_validate_values(hid, HID_OUTPUT_REPORT,
+				     STADIA_FF_REPORT_ID, 0, 2);
+	if (!report)
+		return -ENODEV;
+
+	stadiaff = devm_kzalloc(&hid->dev, sizeof(struct stadiaff_device),
+				GFP_KERNEL);
+	if (!stadiaff)
+		return -ENOMEM;
+
+	hid_set_drvdata(hid, stadiaff);
+
+	input_set_capability(dev, EV_FF, FF_RUMBLE);
+
+	error = input_ff_create_memless(dev, NULL, stadiaff_play);
+	if (error)
+		return error;
+
+	stadiaff->hid = hid;
+	stadiaff->report = report;
+	INIT_WORK(&stadiaff->work, stadiaff_work);
+	disable_work_sync(&stadiaff->work);
+
+	dev->open = stadia_input_open;
+	dev->close = stadia_input_close;
+
+	hid_info(hid, "Force Feedback for Google Stadia controller\n");
+
+	return 0;
+}
+
+static const struct hid_device_id stadia_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_GOOGLE, USB_DEVICE_ID_GOOGLE_STADIA) },
+	{ HID_BLUETOOTH_DEVICE(USB_VENDOR_ID_GOOGLE, USB_DEVICE_ID_GOOGLE_STADIA) },
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, stadia_devices);
+
+static struct hid_driver stadia_driver = {
+	.name = "stadia",
+	.id_table = stadia_devices,
+	.input_configured = stadia_input_configured,
+};
+module_hid_driver(stadia_driver);
+
+MODULE_DESCRIPTION("Google Stadia controller rumble support.");
+MODULE_LICENSE("GPL");