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, 113 insertions, 0 deletions

diff --git a/drivers/hid/hid-gembird.c b/drivers/hid/hid-gembird.c
new file mode 100644
index 000000000..20a8de766
--- /dev/null
+++ b/drivers/hid/hid-gembird.c
@@ -0,0 +1,113 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  HID driver for Gembird Joypad, "PC Game Controller"
+ *
+ *  Copyright (c) 2015 Red Hat, Inc
+ *  Copyright (c) 2015 Benjamin Tissoires
+ */
+
+/*
+ */
+
+#include <linux/device.h>
+#include <linux/hid.h>
+#include <linux/module.h>
+
+#include "hid-ids.h"
+
+#define GEMBIRD_START_FAULTY_RDESC	8
+
+static const __u8 gembird_jpd_faulty_rdesc[] = {
+	0x75, 0x08,			/*   Report Size (8)		*/
+	0x95, 0x05,			/*   Report Count (5)		*/
+	0x15, 0x00,			/*   Logical Minimum (0)	*/
+	0x26, 0xff, 0x00,		/*   Logical Maximum (255)	*/
+	0x35, 0x00,			/*   Physical Minimum (0)	*/
+	0x46, 0xff, 0x00,		/*   Physical Maximum (255)	*/
+	0x09, 0x30,			/*   Usage (X)			*/
+	0x09, 0x31,			/*   Usage (Y)			*/
+	0x09, 0x32,			/*   Usage (Z)			*/
+	0x09, 0x32,			/*   Usage (Z)			*/
+	0x09, 0x35,			/*   Usage (Rz)			*/
+	0x81, 0x02,			/*   Input (Data,Var,Abs)	*/
+};
+
+/*
+ * we fix the report descriptor by:
+ * - marking the first Z axis as constant (so it is ignored by HID)
+ * - assign the original second Z to Rx
+ * - assign the original Rz to Ry
+ */
+static const __u8 gembird_jpd_fixed_rdesc[] = {
+	0x75, 0x08,			/*   Report Size (8)		*/
+	0x95, 0x02,			/*   Report Count (2)		*/
+	0x15, 0x00,			/*   Logical Minimum (0)	*/
+	0x26, 0xff, 0x00,		/*   Logical Maximum (255)	*/
+	0x35, 0x00,			/*   Physical Minimum (0)	*/
+	0x46, 0xff, 0x00,		/*   Physical Maximum (255)	*/
+	0x09, 0x30,			/*   Usage (X)			*/
+	0x09, 0x31,			/*   Usage (Y)			*/
+	0x81, 0x02,			/*   Input (Data,Var,Abs)	*/
+	0x95, 0x01,			/*   Report Count (1)		*/
+	0x09, 0x32,			/*   Usage (Z)			*/
+	0x81, 0x01,			/*   Input (Cnst,Arr,Abs)	*/
+	0x95, 0x02,			/*   Report Count (2)		*/
+	0x09, 0x33,			/*   Usage (Rx)			*/
+	0x09, 0x34,			/*   Usage (Ry)			*/
+	0x81, 0x02,			/*   Input (Data,Var,Abs)	*/
+};
+
+static const __u8 *gembird_report_fixup(struct hid_device *hdev, __u8 *rdesc,
+		unsigned int *rsize)
+{
+	__u8 *new_rdesc;
+	/* delta_size is > 0 */
+	size_t delta_size = sizeof(gembird_jpd_fixed_rdesc) -
+			    sizeof(gembird_jpd_faulty_rdesc);
+	size_t new_size = *rsize + delta_size;
+
+	if (*rsize >= 31 && !memcmp(&rdesc[GEMBIRD_START_FAULTY_RDESC],
+				    gembird_jpd_faulty_rdesc,
+				    sizeof(gembird_jpd_faulty_rdesc))) {
+		new_rdesc = devm_kzalloc(&hdev->dev, new_size, GFP_KERNEL);
+		if (new_rdesc == NULL)
+			return rdesc;
+
+		dev_info(&hdev->dev,
+			 "fixing Gembird JPD-DualForce 2 report descriptor.\n");
+
+		/* start by copying the end of the rdesc */
+		memcpy(new_rdesc + delta_size, rdesc, *rsize);
+
+		/* add the correct beginning */
+		memcpy(new_rdesc, rdesc, GEMBIRD_START_FAULTY_RDESC);
+
+		/* replace the faulty part with the fixed one */
+		memcpy(new_rdesc + GEMBIRD_START_FAULTY_RDESC,
+		       gembird_jpd_fixed_rdesc,
+		       sizeof(gembird_jpd_fixed_rdesc));
+
+		*rsize = new_size;
+		rdesc = new_rdesc;
+	}
+
+	return rdesc;
+}
+
+static const struct hid_device_id gembird_devices[] = {
+	{ HID_USB_DEVICE(USB_VENDOR_ID_GEMBIRD,
+			 USB_DEVICE_ID_GEMBIRD_JPD_DUALFORCE2) },
+	{ }
+};
+MODULE_DEVICE_TABLE(hid, gembird_devices);
+
+static struct hid_driver gembird_driver = {
+	.name = "gembird",
+	.id_table = gembird_devices,
+	.report_fixup = gembird_report_fixup,
+};
+module_hid_driver(gembird_driver);
+
+MODULE_AUTHOR("Benjamin Tissoires <benjamin.tissoires@gmail.com>");
+MODULE_DESCRIPTION("HID Gembird joypad driver");
+MODULE_LICENSE("GPL");