KVM: SEV: Do cache maintenance on the source VM during intra-host migrationgrafted

Manually perform cache maintenance on the source VM during intra-host
migration to ensure no stale data is left in CPU caches after the VM is
destroyed.  Because the source VM is "converted" to a non-SEV VM, KVM's
memory reclaim flows won't trigger cache maintenance, e.g. when all guest
memory is reclaimed in response to detaching from the mmu_notifier.

Note, relying on the destination VM to do cache maintenance isn't an option
as KVM doesn't require identical guest memory configurations, i.e. the
source VM may have access to memory that the destination VM does not.
Enforcing equivalent memory configurations is infeasible, as it would
require a *deep* comparison of memslots, e.g. to verify that not only are
the memslot identical, but what the memslots point at is also identical.

Fixes: b56639318bb2 ("KVM: SEV: Add support for SEV intra host migration")
Cc: stable@vger.kernel.org
Reported-by: Stefan Teodorescu <fane@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20260923163721.1584779-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.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");