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, 218 insertions, 0 deletions

diff --git a/drivers/usb/atm/xusbatm.c b/drivers/usb/atm/xusbatm.c
new file mode 100644
index 000000000..5c1e1f521
--- /dev/null
+++ b/drivers/usb/atm/xusbatm.c
@@ -0,0 +1,218 @@
+// SPDX-License-Identifier: GPL-2.0+
+/******************************************************************************
+ *  xusbatm.c -	dumb usbatm-based driver for modems initialized in userspace
+ *
+ *  Copyright (C) 2005 Duncan Sands, Roman Kagan (rkagan % mail ! ru)
+ ******************************************************************************/
+
+#include <linux/module.h>
+#include <linux/etherdevice.h>		/* for eth_random_addr() */
+
+#include "usbatm.h"
+
+
+#define XUSBATM_DRIVERS_MAX	8
+
+#define XUSBATM_PARM(name, type, parmtype, desc) \
+	static type name[XUSBATM_DRIVERS_MAX]; \
+	static unsigned int num_##name; \
+	module_param_array(name, parmtype, &num_##name, 0444); \
+	MODULE_PARM_DESC(name, desc)
+
+XUSBATM_PARM(vendor, unsigned short, ushort, "USB device vendor");
+XUSBATM_PARM(product, unsigned short, ushort, "USB device product");
+
+XUSBATM_PARM(rx_endpoint, unsigned char, byte, "rx endpoint number");
+XUSBATM_PARM(tx_endpoint, unsigned char, byte, "tx endpoint number");
+XUSBATM_PARM(rx_padding, unsigned char, byte, "rx padding (default 0)");
+XUSBATM_PARM(tx_padding, unsigned char, byte, "tx padding (default 0)");
+XUSBATM_PARM(rx_altsetting, unsigned char, byte, "rx altsetting (default 0)");
+XUSBATM_PARM(tx_altsetting, unsigned char, byte, "rx altsetting (default 0)");
+
+static const char xusbatm_driver_name[] = "xusbatm";
+
+static struct usbatm_driver xusbatm_drivers[XUSBATM_DRIVERS_MAX];
+static struct usb_device_id xusbatm_usb_ids[XUSBATM_DRIVERS_MAX + 1];
+static struct usb_driver xusbatm_usb_driver;
+
+static struct usb_interface *xusbatm_find_intf(struct usb_device *usb_dev, int altsetting, u8 ep)
+{
+	struct usb_host_interface *alt;
+	struct usb_interface *intf;
+	int i, j;
+
+	for (i = 0; i < usb_dev->actconfig->desc.bNumInterfaces; i++)
+		if ((intf = usb_dev->actconfig->interface[i]) && (alt = usb_altnum_to_altsetting(intf, altsetting)))
+			for (j = 0; j < alt->desc.bNumEndpoints; j++)
+				if (alt->endpoint[j].desc.bEndpointAddress == ep)
+					return intf;
+	return NULL;
+}
+
+static int xusbatm_capture_intf(struct usbatm_data *usbatm, struct usb_device *usb_dev,
+		struct usb_interface *intf, int altsetting, int claim)
+{
+	int ifnum = intf->altsetting->desc.bInterfaceNumber;
+	int ret;
+
+	if (claim && (ret = usb_driver_claim_interface(&xusbatm_usb_driver, intf, usbatm))) {
+		usb_err(usbatm, "%s: failed to claim interface %2d (%d)!\n", __func__, ifnum, ret);
+		return ret;
+	}
+	ret = usb_set_interface(usb_dev, ifnum, altsetting);
+	if (ret) {
+		usb_err(usbatm, "%s: altsetting %2d for interface %2d failed (%d)!\n", __func__, altsetting, ifnum, ret);
+		return ret;
+	}
+	return 0;
+}
+
+static void xusbatm_release_intf(struct usb_device *usb_dev, struct usb_interface *intf, int claimed)
+{
+	if (claimed) {
+		usb_set_intfdata(intf, NULL);
+		usb_driver_release_interface(&xusbatm_usb_driver, intf);
+	}
+}
+
+static int xusbatm_bind(struct usbatm_data *usbatm,
+			struct usb_interface *intf, const struct usb_device_id *id)
+{
+	struct usb_device *usb_dev = interface_to_usbdev(intf);
+	int drv_ix = id->driver_info;
+	int rx_alt = rx_altsetting[drv_ix];
+	int tx_alt = tx_altsetting[drv_ix];
+	struct usb_interface *rx_intf = xusbatm_find_intf(usb_dev, rx_alt, rx_endpoint[drv_ix]);
+	struct usb_interface *tx_intf = xusbatm_find_intf(usb_dev, tx_alt, tx_endpoint[drv_ix]);
+	int ret;
+
+	usb_dbg(usbatm, "%s: binding driver %d: vendor %04x product %04x"
+		" rx: ep %02x padd %d alt %2d tx: ep %02x padd %d alt %2d\n",
+		__func__, drv_ix, vendor[drv_ix], product[drv_ix],
+		rx_endpoint[drv_ix], rx_padding[drv_ix], rx_alt,
+		tx_endpoint[drv_ix], tx_padding[drv_ix], tx_alt);
+
+	if (!rx_intf || !tx_intf) {
+		if (!rx_intf)
+			usb_dbg(usbatm, "%s: no interface contains endpoint %02x in altsetting %2d\n",
+				__func__, rx_endpoint[drv_ix], rx_alt);
+		if (!tx_intf)
+			usb_dbg(usbatm, "%s: no interface contains endpoint %02x in altsetting %2d\n",
+				__func__, tx_endpoint[drv_ix], tx_alt);
+		return -ENODEV;
+	}
+
+	if ((rx_intf != intf) && (tx_intf != intf))
+		return -ENODEV;
+
+	if ((rx_intf == tx_intf) && (rx_alt != tx_alt)) {
+		usb_err(usbatm, "%s: altsettings clash on interface %2d (%2d vs %2d)!\n", __func__,
+				rx_intf->altsetting->desc.bInterfaceNumber, rx_alt, tx_alt);
+		return -EINVAL;
+	}
+
+	usb_dbg(usbatm, "%s: rx If#=%2d; tx If#=%2d\n", __func__,
+			rx_intf->altsetting->desc.bInterfaceNumber,
+			tx_intf->altsetting->desc.bInterfaceNumber);
+
+	ret = xusbatm_capture_intf(usbatm, usb_dev, rx_intf, rx_alt, rx_intf != intf);
+	if (ret)
+		return ret;
+
+	if ((tx_intf != rx_intf) && (ret = xusbatm_capture_intf(usbatm, usb_dev, tx_intf, tx_alt, tx_intf != intf))) {
+		xusbatm_release_intf(usb_dev, rx_intf, rx_intf != intf);
+		return ret;
+	}
+
+	return 0;
+}
+
+static void xusbatm_unbind(struct usbatm_data *usbatm,
+			   struct usb_interface *intf)
+{
+	struct usb_device *usb_dev = interface_to_usbdev(intf);
+	int i;
+
+	usb_dbg(usbatm, "%s entered\n", __func__);
+
+	for (i = 0; i < usb_dev->actconfig->desc.bNumInterfaces; i++) {
+		struct usb_interface *cur_intf = usb_dev->actconfig->interface[i];
+
+		if (cur_intf && (usb_get_intfdata(cur_intf) == usbatm)) {
+			usb_set_intfdata(cur_intf, NULL);
+			usb_driver_release_interface(&xusbatm_usb_driver, cur_intf);
+		}
+	}
+}
+
+static int xusbatm_atm_start(struct usbatm_data *usbatm,
+			     struct atm_dev *atm_dev)
+{
+	atm_dbg(usbatm, "%s entered\n", __func__);
+
+	/* use random MAC as we've no way to get it from the device */
+	eth_random_addr(atm_dev->esi);
+
+	return 0;
+}
+
+
+static int xusbatm_usb_probe(struct usb_interface *intf,
+			     const struct usb_device_id *id)
+{
+	return usbatm_usb_probe(intf, id,
+				xusbatm_drivers + (id - xusbatm_usb_ids));
+}
+
+static struct usb_driver xusbatm_usb_driver = {
+	.name		= xusbatm_driver_name,
+	.probe		= xusbatm_usb_probe,
+	.disconnect	= usbatm_usb_disconnect,
+	.id_table	= xusbatm_usb_ids,
+	.no_dynamic_id	= 1,
+};
+
+static int __init xusbatm_init(void)
+{
+	int i;
+
+	if (!num_vendor ||
+	    num_vendor != num_product ||
+	    num_vendor != num_rx_endpoint ||
+	    num_vendor != num_tx_endpoint) {
+		pr_warn("xusbatm: malformed module parameters\n");
+		return -EINVAL;
+	}
+
+	for (i = 0; i < num_vendor; i++) {
+		rx_endpoint[i] |= USB_DIR_IN;
+		tx_endpoint[i] &= USB_ENDPOINT_NUMBER_MASK;
+
+		xusbatm_usb_ids[i].match_flags	= USB_DEVICE_ID_MATCH_DEVICE;
+		xusbatm_usb_ids[i].idVendor	= vendor[i];
+		xusbatm_usb_ids[i].idProduct	= product[i];
+		xusbatm_usb_ids[i].driver_info	= i;
+
+		xusbatm_drivers[i].driver_name	= xusbatm_driver_name;
+		xusbatm_drivers[i].bind		= xusbatm_bind;
+		xusbatm_drivers[i].unbind	= xusbatm_unbind;
+		xusbatm_drivers[i].atm_start	= xusbatm_atm_start;
+		xusbatm_drivers[i].bulk_in	= rx_endpoint[i];
+		xusbatm_drivers[i].bulk_out	= tx_endpoint[i];
+		xusbatm_drivers[i].rx_padding	= rx_padding[i];
+		xusbatm_drivers[i].tx_padding	= tx_padding[i];
+	}
+
+	return usb_register(&xusbatm_usb_driver);
+}
+module_init(xusbatm_init);
+
+static void __exit xusbatm_exit(void)
+{
+	usb_deregister(&xusbatm_usb_driver);
+}
+module_exit(xusbatm_exit);
+
+MODULE_AUTHOR("Roman Kagan, Duncan Sands");
+MODULE_DESCRIPTION("Driver for USB ADSL modems initialized in userspace");
+MODULE_LICENSE("GPL");