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, 395 insertions, 0 deletions

diff --git a/drivers/usb/misc/usbsevseg.c b/drivers/usb/misc/usbsevseg.c
new file mode 100644
index 000000000..89d25fcef
--- /dev/null
+++ b/drivers/usb/misc/usbsevseg.c
@@ -0,0 +1,395 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * USB 7 Segment Driver
+ *
+ * Copyright (C) 2008 Harrison Metzger <harrisonmetz@gmail.com>
+ * Based on usbled.c by Greg Kroah-Hartman (greg@kroah.com)
+ */
+
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/string.h>
+#include <linux/usb.h>
+
+
+#define DRIVER_AUTHOR "Harrison Metzger <harrisonmetz@gmail.com>"
+#define DRIVER_DESC "USB 7 Segment Driver"
+
+#define VENDOR_ID	0x0fc5
+#define PRODUCT_ID	0x1227
+#define MAXLEN		8
+
+/* table of devices that work with this driver */
+static const struct usb_device_id id_table[] = {
+	{ USB_DEVICE(VENDOR_ID, PRODUCT_ID) },
+	{ },
+};
+MODULE_DEVICE_TABLE(usb, id_table);
+
+/* the different text display modes the device is capable of */
+static const char *display_textmodes[] = {"raw", "hex", "ascii"};
+
+struct usb_sevsegdev {
+	struct usb_device *udev;
+	struct usb_interface *intf;
+
+	u8 powered;
+	u8 mode_msb;
+	u8 mode_lsb;
+	u8 decimals[MAXLEN];
+	u8 textmode;
+	u8 text[MAXLEN];
+	u16 textlength;
+
+	u8 shadow_power; /* for PM */
+	u8 has_interface_pm;
+};
+
+/* sysfs_streq can't replace this completely
+ * If the device was in hex mode, and the user wanted a 0,
+ * if str commands are used, we would assume the end of string
+ * so mem commands are used.
+ */
+static inline size_t my_memlen(const char *buf, size_t count)
+{
+	if (count > 0 && buf[count-1] == '\n')
+		return count - 1;
+	else
+		return count;
+}
+
+static void update_display_powered(struct usb_sevsegdev *mydev)
+{
+	int rc;
+
+	if (mydev->powered && !mydev->has_interface_pm) {
+		rc = usb_autopm_get_interface(mydev->intf);
+		if (rc < 0)
+			return;
+		mydev->has_interface_pm = 1;
+	}
+
+	if (mydev->shadow_power != 1)
+		return;
+
+	rc = usb_control_msg_send(mydev->udev, 0, 0x12, 0x48,
+				  (80 * 0x100) + 10, /*  (power mode) */
+				  (0x00 * 0x100) + (mydev->powered ? 1 : 0),
+				  NULL, 0, 2000, GFP_KERNEL);
+	if (rc < 0)
+		dev_dbg(&mydev->udev->dev, "power retval = %d\n", rc);
+
+	if (!mydev->powered && mydev->has_interface_pm) {
+		usb_autopm_put_interface(mydev->intf);
+		mydev->has_interface_pm = 0;
+	}
+}
+
+static void update_display_mode(struct usb_sevsegdev *mydev)
+{
+	int rc;
+
+	if(mydev->shadow_power != 1)
+		return;
+
+	rc = usb_control_msg_send(mydev->udev, 0, 0x12, 0x48,
+				  (82 * 0x100) + 10, /* (set mode) */
+				  (mydev->mode_msb * 0x100) + mydev->mode_lsb,
+				  NULL, 0, 2000, GFP_NOIO);
+
+	if (rc < 0)
+		dev_dbg(&mydev->udev->dev, "mode retval = %d\n", rc);
+}
+
+static void update_display_visual(struct usb_sevsegdev *mydev, gfp_t mf)
+{
+	int rc;
+	int i;
+	unsigned char buffer[MAXLEN] = {0};
+	u8 decimals = 0;
+
+	if(mydev->shadow_power != 1)
+		return;
+
+	/* The device is right to left, where as you write left to right */
+	for (i = 0; i < mydev->textlength; i++)
+		buffer[i] = mydev->text[mydev->textlength-1-i];
+
+	rc = usb_control_msg_send(mydev->udev, 0, 0x12, 0x48,
+				  (85 * 0x100) + 10, /* (write text) */
+				  (0 * 0x100) + mydev->textmode, /* mode  */
+				  &buffer, mydev->textlength, 2000, mf);
+
+	if (rc < 0)
+		dev_dbg(&mydev->udev->dev, "write retval = %d\n", rc);
+
+	/* The device is right to left, where as you write left to right */
+	for (i = 0; i < sizeof(mydev->decimals); i++)
+		decimals |= mydev->decimals[i] << i;
+
+	rc = usb_control_msg_send(mydev->udev, 0, 0x12, 0x48,
+				  (86 * 0x100) + 10, /* (set decimal) */
+				  (0 * 0x100) + decimals, /* decimals */
+				  NULL, 0, 2000, mf);
+
+	if (rc < 0)
+		dev_dbg(&mydev->udev->dev, "decimal retval = %d\n", rc);
+}
+
+#define MYDEV_ATTR_SIMPLE_UNSIGNED(name, update_fcn)		\
+static ssize_t name##_show(struct device *dev,			\
+	struct device_attribute *attr, char *buf) 		\
+{								\
+	struct usb_interface *intf = to_usb_interface(dev);	\
+	struct usb_sevsegdev *mydev = usb_get_intfdata(intf);	\
+								\
+	return sprintf(buf, "%u\n", mydev->name);		\
+}								\
+								\
+static ssize_t name##_store(struct device *dev,			\
+	struct device_attribute *attr, const char *buf, size_t count) \
+{								\
+	struct usb_interface *intf = to_usb_interface(dev);	\
+	struct usb_sevsegdev *mydev = usb_get_intfdata(intf);	\
+								\
+	mydev->name = simple_strtoul(buf, NULL, 10);		\
+	update_fcn(mydev); 					\
+								\
+	return count;						\
+}								\
+static DEVICE_ATTR_RW(name);
+
+static ssize_t text_show(struct device *dev,
+	struct device_attribute *attr, char *buf)
+{
+	struct usb_interface *intf = to_usb_interface(dev);
+	struct usb_sevsegdev *mydev = usb_get_intfdata(intf);
+
+	return sysfs_emit(buf, "%s\n", mydev->text);
+}
+
+static ssize_t text_store(struct device *dev,
+	struct device_attribute *attr, const char *buf, size_t count)
+{
+	struct usb_interface *intf = to_usb_interface(dev);
+	struct usb_sevsegdev *mydev = usb_get_intfdata(intf);
+	size_t end = my_memlen(buf, count);
+
+	if (end > sizeof(mydev->text))
+		return -EINVAL;
+
+	memset(mydev->text, 0, sizeof(mydev->text));
+	mydev->textlength = end;
+
+	if (end > 0)
+		memcpy(mydev->text, buf, end);
+
+	update_display_visual(mydev, GFP_KERNEL);
+	return count;
+}
+
+static DEVICE_ATTR_RW(text);
+
+static ssize_t decimals_show(struct device *dev,
+	struct device_attribute *attr, char *buf)
+{
+	struct usb_interface *intf = to_usb_interface(dev);
+	struct usb_sevsegdev *mydev = usb_get_intfdata(intf);
+	int i;
+	int pos;
+
+	for (i = 0; i < sizeof(mydev->decimals); i++) {
+		pos = sizeof(mydev->decimals) - 1 - i;
+		if (mydev->decimals[i] == 0)
+			buf[pos] = '0';
+		else if (mydev->decimals[i] == 1)
+			buf[pos] = '1';
+		else
+			buf[pos] = 'x';
+	}
+
+	buf[sizeof(mydev->decimals)] = '\n';
+	return sizeof(mydev->decimals) + 1;
+}
+
+static ssize_t decimals_store(struct device *dev,
+	struct device_attribute *attr, const char *buf, size_t count)
+{
+	struct usb_interface *intf = to_usb_interface(dev);
+	struct usb_sevsegdev *mydev = usb_get_intfdata(intf);
+	size_t end = my_memlen(buf, count);
+	int i;
+
+	if (end > sizeof(mydev->decimals))
+		return -EINVAL;
+
+	for (i = 0; i < end; i++)
+		if (buf[i] != '0' && buf[i] != '1')
+			return -EINVAL;
+
+	memset(mydev->decimals, 0, sizeof(mydev->decimals));
+	for (i = 0; i < end; i++)
+		if (buf[i] == '1')
+			mydev->decimals[end-1-i] = 1;
+
+	update_display_visual(mydev, GFP_KERNEL);
+
+	return count;
+}
+
+static DEVICE_ATTR_RW(decimals);
+
+static ssize_t textmode_show(struct device *dev,
+	struct device_attribute *attr, char *buf)
+{
+	struct usb_interface *intf = to_usb_interface(dev);
+	struct usb_sevsegdev *mydev = usb_get_intfdata(intf);
+	int i;
+
+	buf[0] = 0;
+
+	for (i = 0; i < ARRAY_SIZE(display_textmodes); i++) {
+		if (mydev->textmode == i) {
+			strcat(buf, " [");
+			strcat(buf, display_textmodes[i]);
+			strcat(buf, "] ");
+		} else {
+			strcat(buf, " ");
+			strcat(buf, display_textmodes[i]);
+			strcat(buf, " ");
+		}
+	}
+	strcat(buf, "\n");
+
+
+	return strlen(buf);
+}
+
+static ssize_t textmode_store(struct device *dev,
+	struct device_attribute *attr, const char *buf, size_t count)
+{
+	struct usb_interface *intf = to_usb_interface(dev);
+	struct usb_sevsegdev *mydev = usb_get_intfdata(intf);
+	int i;
+
+	i = sysfs_match_string(display_textmodes, buf);
+	if (i < 0)
+		return i;
+
+	mydev->textmode = i;
+	update_display_visual(mydev, GFP_KERNEL);
+	return count;
+}
+
+static DEVICE_ATTR_RW(textmode);
+
+
+MYDEV_ATTR_SIMPLE_UNSIGNED(powered, update_display_powered);
+MYDEV_ATTR_SIMPLE_UNSIGNED(mode_msb, update_display_mode);
+MYDEV_ATTR_SIMPLE_UNSIGNED(mode_lsb, update_display_mode);
+
+static struct attribute *sevseg_attrs[] = {
+	&dev_attr_powered.attr,
+	&dev_attr_text.attr,
+	&dev_attr_textmode.attr,
+	&dev_attr_decimals.attr,
+	&dev_attr_mode_msb.attr,
+	&dev_attr_mode_lsb.attr,
+	NULL
+};
+ATTRIBUTE_GROUPS(sevseg);
+
+static int sevseg_probe(struct usb_interface *interface,
+	const struct usb_device_id *id)
+{
+	struct usb_device *udev = interface_to_usbdev(interface);
+	struct usb_sevsegdev *mydev;
+	int rc = -ENOMEM;
+
+	mydev = kzalloc_obj(struct usb_sevsegdev);
+	if (!mydev)
+		goto error_mem;
+
+	mydev->udev = udev;
+	mydev->intf = interface;
+	usb_set_intfdata(interface, mydev);
+
+	/* PM */
+	mydev->shadow_power = 1; /* currently active */
+	mydev->has_interface_pm = 0; /* have not issued autopm_get */
+
+	/*set defaults */
+	mydev->textmode = 0x02; /* ascii mode */
+	mydev->mode_msb = 0x06; /* 6 characters */
+	mydev->mode_lsb = 0x3f; /* scanmode for 6 chars */
+
+	dev_info(&interface->dev, "USB 7 Segment device now attached\n");
+	return 0;
+
+error_mem:
+	return rc;
+}
+
+static void sevseg_disconnect(struct usb_interface *interface)
+{
+	struct usb_sevsegdev *mydev;
+
+	mydev = usb_get_intfdata(interface);
+	usb_set_intfdata(interface, NULL);
+	kfree(mydev);
+	dev_info(&interface->dev, "USB 7 Segment now disconnected\n");
+}
+
+static int sevseg_suspend(struct usb_interface *intf, pm_message_t message)
+{
+	struct usb_sevsegdev *mydev;
+
+	mydev = usb_get_intfdata(intf);
+	mydev->shadow_power = 0;
+
+	return 0;
+}
+
+static int sevseg_resume(struct usb_interface *intf)
+{
+	struct usb_sevsegdev *mydev;
+
+	mydev = usb_get_intfdata(intf);
+	mydev->shadow_power = 1;
+	update_display_mode(mydev);
+	update_display_visual(mydev, GFP_NOIO);
+
+	return 0;
+}
+
+static int sevseg_reset_resume(struct usb_interface *intf)
+{
+	struct usb_sevsegdev *mydev;
+
+	mydev = usb_get_intfdata(intf);
+	mydev->shadow_power = 1;
+	update_display_mode(mydev);
+	update_display_visual(mydev, GFP_NOIO);
+
+	return 0;
+}
+
+static struct usb_driver sevseg_driver = {
+	.name =		"usbsevseg",
+	.probe =	sevseg_probe,
+	.disconnect =	sevseg_disconnect,
+	.suspend =	sevseg_suspend,
+	.resume =	sevseg_resume,
+	.reset_resume =	sevseg_reset_resume,
+	.id_table =	id_table,
+	.dev_groups =	sevseg_groups,
+	.supports_autosuspend = 1,
+};
+
+module_usb_driver(sevseg_driver);
+
+MODULE_AUTHOR(DRIVER_AUTHOR);
+MODULE_DESCRIPTION(DRIVER_DESC);
+MODULE_LICENSE("GPL");