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, 98 insertions, 0 deletions

diff --git a/drivers/hid/hid-retrode.c b/drivers/hid/hid-retrode.c
new file mode 100644
index 000000000..7997627fd
--- /dev/null
+++ b/drivers/hid/hid-retrode.c
@@ -0,0 +1,98 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  HID driver for Retrode 2 controller adapter and plug-in extensions
+ *
+ *  Copyright (c) 2017 Bastien Nocera <hadess@hadess.net>
+ */
+
+/*
+ */
+
+#include <linux/input.h>
+#include <linux/slab.h>
+#include <linux/hid.h>
+#include <linux/module.h>
+#include "hid-ids.h"
+
+#define CONTROLLER_NAME_BASE "Retrode"
+
+static int retrode_input_configured(struct hid_device *hdev,
+					struct hid_input *hi)
+{
+	struct hid_field *field = hi->report->field[0];
+	const char *suffix;
+	int number = 0;
+	char *name;
+
+	switch (field->report->id) {
+	case 0:
+		suffix = "SNES Mouse";
+		break;
+	case 1:
+	case 2:
+		suffix = "SNES / N64";
+		number = field->report->id;
+		break;
+	case 3:
+	case 4:
+		suffix = "Mega Drive";
+		number = field->report->id - 2;
+		break;
+	default:
+		hid_err(hdev, "Got unhandled report id %d\n", field->report->id);
+		suffix = "Unknown";
+	}
+
+	if (number)
+		name = devm_kasprintf(&hdev->dev, GFP_KERNEL,
+				"%s %s #%d", CONTROLLER_NAME_BASE,
+				suffix, number);
+	else
+		name = devm_kasprintf(&hdev->dev, GFP_KERNEL,
+				"%s %s", CONTROLLER_NAME_BASE, suffix);
+
+	if (!name)
+		return -ENOMEM;
+
+	hi->input->name = name;
+
+	return 0;
+}
+
+static int retrode_probe(struct hid_device *hdev,
+			const struct hid_device_id *id)
+{
+
+	int ret;
+
+	/* Has no effect on the mouse device */
+	hdev->quirks |= HID_QUIRK_MULTI_INPUT;
+
+	ret = hid_parse(hdev);
+	if (ret)
+		return ret;
+
+	ret = hid_hw_start(hdev, HID_CONNECT_DEFAULT);
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+static const struct hid_device_id retrode_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_FUTURE_TECHNOLOGY, USB_DEVICE_ID_RETRODE2) },
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, retrode_devices);
+
+static struct hid_driver retrode_driver = {
+	.name             = "hid-retrode",
+	.id_table         = retrode_devices,
+	.input_configured = retrode_input_configured,
+	.probe            = retrode_probe,
+};
+
+module_hid_driver(retrode_driver);
+
+MODULE_DESCRIPTION("HID driver for Retrode 2 controller adapter and plug-in extensions");
+MODULE_LICENSE("GPL");