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, 472 insertions, 0 deletions

diff --git a/drivers/hid/hid-roccat.c b/drivers/hid/hid-roccat.c
new file mode 100644
index 000000000..4f15eb951
--- /dev/null
+++ b/drivers/hid/hid-roccat.c
@@ -0,0 +1,472 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Roccat driver for Linux
+ *
+ * Copyright (c) 2010 Stefan Achatz <erazor_de@users.sourceforge.net>
+ */
+
+/*
+ */
+
+/*
+ * Module roccat is a char device used to report special events of roccat
+ * hardware to userland. These events include requests for on-screen-display of
+ * profile or dpi settings or requests for execution of macro sequences that are
+ * not stored in device. The information in these events depends on hid device
+ * implementation and contains data that is not available in a single hid event
+ * or else hidraw could have been used.
+ * It is inspired by hidraw, but uses only one circular buffer for all readers.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/cdev.h>
+#include <linux/poll.h>
+#include <linux/sched/signal.h>
+#include <linux/hid-roccat.h>
+#include <linux/module.h>
+
+#define ROCCAT_FIRST_MINOR 0
+#define ROCCAT_MAX_DEVICES 8
+
+/* should be a power of 2 for performance reason */
+#define ROCCAT_CBUF_SIZE 16
+
+struct roccat_report {
+	uint8_t *value;
+};
+
+struct roccat_device {
+	unsigned int minor;
+	int report_size;
+	int open;
+	int exist;
+	wait_queue_head_t wait;
+	struct device *dev;
+	struct hid_device *hid;
+	struct list_head readers;
+	/* protects modifications of readers list */
+	struct mutex readers_lock;
+
+	/*
+	 * circular_buffer has one writer and multiple readers with their own
+	 * read pointers
+	 */
+	struct roccat_report cbuf[ROCCAT_CBUF_SIZE];
+	int cbuf_end;
+	struct mutex cbuf_lock;
+};
+
+struct roccat_reader {
+	struct list_head node;
+	struct roccat_device *device;
+	int cbuf_start;
+};
+
+static int roccat_major;
+static struct cdev roccat_cdev;
+
+static struct roccat_device *devices[ROCCAT_MAX_DEVICES];
+/* protects modifications of devices array */
+static DEFINE_MUTEX(devices_lock);
+
+static void roccat_free_device(struct roccat_device *device)
+{
+	int i;
+
+	for (i = 0; i < ROCCAT_CBUF_SIZE; i++)
+		kfree(device->cbuf[i].value);
+	kfree(device);
+}
+
+static ssize_t roccat_read(struct file *file, char __user *buffer,
+		size_t count, loff_t *ppos)
+{
+	struct roccat_reader *reader = file->private_data;
+	struct roccat_device *device = reader->device;
+	struct roccat_report *report;
+	ssize_t retval = 0, len;
+	DECLARE_WAITQUEUE(wait, current);
+
+	mutex_lock(&device->cbuf_lock);
+
+	/* no data? */
+	if (reader->cbuf_start == device->cbuf_end) {
+		add_wait_queue(&device->wait, &wait);
+		set_current_state(TASK_INTERRUPTIBLE);
+
+		/* wait for data */
+		while (reader->cbuf_start == device->cbuf_end) {
+			if (file->f_flags & O_NONBLOCK) {
+				retval = -EAGAIN;
+				break;
+			}
+			if (signal_pending(current)) {
+				retval = -ERESTARTSYS;
+				break;
+			}
+			if (!device->exist) {
+				retval = -EIO;
+				break;
+			}
+
+			mutex_unlock(&device->cbuf_lock);
+			schedule();
+			mutex_lock(&device->cbuf_lock);
+			set_current_state(TASK_INTERRUPTIBLE);
+		}
+
+		set_current_state(TASK_RUNNING);
+		remove_wait_queue(&device->wait, &wait);
+	}
+
+	/* here we either have data or a reason to return if retval is set */
+	if (retval)
+		goto exit_unlock;
+
+	report = &device->cbuf[reader->cbuf_start];
+	/*
+	 * If report is larger than requested amount of data, rest of report
+	 * is lost!
+	 */
+	len = device->report_size > count ? count : device->report_size;
+
+	if (copy_to_user(buffer, report->value, len)) {
+		retval = -EFAULT;
+		goto exit_unlock;
+	}
+	retval += len;
+	reader->cbuf_start = (reader->cbuf_start + 1) % ROCCAT_CBUF_SIZE;
+
+exit_unlock:
+	mutex_unlock(&device->cbuf_lock);
+	return retval;
+}
+
+static __poll_t roccat_poll(struct file *file, poll_table *wait)
+{
+	struct roccat_reader *reader = file->private_data;
+	poll_wait(file, &reader->device->wait, wait);
+	if (reader->cbuf_start != reader->device->cbuf_end)
+		return EPOLLIN | EPOLLRDNORM;
+	if (!reader->device->exist)
+		return EPOLLERR | EPOLLHUP;
+	return 0;
+}
+
+static int roccat_open(struct inode *inode, struct file *file)
+{
+	unsigned int minor = iminor(inode);
+	struct roccat_reader *reader;
+	struct roccat_device *device;
+	int error = 0;
+
+	reader = kzalloc_obj(struct roccat_reader);
+	if (!reader)
+		return -ENOMEM;
+
+	mutex_lock(&devices_lock);
+
+	device = devices[minor];
+
+	if (!device) {
+		pr_emerg("roccat device with minor %d doesn't exist\n", minor);
+		error = -ENODEV;
+		goto exit_err_devices;
+	}
+
+	mutex_lock(&device->readers_lock);
+
+	if (!device->open++) {
+		/* power on device on adding first reader */
+		error = hid_hw_power(device->hid, PM_HINT_FULLON);
+		if (error < 0) {
+			--device->open;
+			goto exit_err_readers;
+		}
+
+		error = hid_hw_open(device->hid);
+		if (error < 0) {
+			hid_hw_power(device->hid, PM_HINT_NORMAL);
+			--device->open;
+			goto exit_err_readers;
+		}
+	}
+
+	reader->device = device;
+	/* new reader doesn't get old events */
+	reader->cbuf_start = device->cbuf_end;
+
+	list_add_tail(&reader->node, &device->readers);
+	file->private_data = reader;
+
+exit_err_readers:
+	mutex_unlock(&device->readers_lock);
+exit_err_devices:
+	mutex_unlock(&devices_lock);
+	if (error)
+		kfree(reader);
+	return error;
+}
+
+static int roccat_release(struct inode *inode, struct file *file)
+{
+	unsigned int minor = iminor(inode);
+	struct roccat_reader *reader = file->private_data;
+	struct roccat_device *device;
+
+	mutex_lock(&devices_lock);
+
+	device = devices[minor];
+	if (!device) {
+		mutex_unlock(&devices_lock);
+		pr_emerg("roccat device with minor %d doesn't exist\n", minor);
+		return -ENODEV;
+	}
+
+	mutex_lock(&device->readers_lock);
+	list_del(&reader->node);
+	mutex_unlock(&device->readers_lock);
+	kfree(reader);
+
+	if (!--device->open) {
+		/* removing last reader */
+		if (device->exist) {
+			hid_hw_power(device->hid, PM_HINT_NORMAL);
+			hid_hw_close(device->hid);
+		} else {
+			roccat_free_device(device);
+		}
+	}
+
+	mutex_unlock(&devices_lock);
+
+	return 0;
+}
+
+/*
+ * roccat_report_event() - output data to readers
+ * @minor: minor device number returned by roccat_connect()
+ * @data: pointer to data
+ *
+ * Return value is zero on success, a negative error code on failure.
+ *
+ * This is called from interrupt handler.
+ */
+int roccat_report_event(int minor, u8 const *data)
+{
+	struct roccat_device *device;
+	struct roccat_reader *reader;
+	struct roccat_report *report;
+	uint8_t *new_value;
+
+	device = devices[minor];
+
+	new_value = kmemdup(data, device->report_size, GFP_ATOMIC);
+	if (!new_value)
+		return -ENOMEM;
+
+	mutex_lock(&device->readers_lock);
+	mutex_lock(&device->cbuf_lock);
+
+	report = &device->cbuf[device->cbuf_end];
+
+	/* passing NULL is safe */
+	kfree(report->value);
+
+	report->value = new_value;
+	device->cbuf_end = (device->cbuf_end + 1) % ROCCAT_CBUF_SIZE;
+
+	list_for_each_entry(reader, &device->readers, node) {
+		/*
+		 * As we already inserted one element, the buffer can't be
+		 * empty. If start and end are equal, buffer is full and we
+		 * increase start, so that slow reader misses one event, but
+		 * gets the newer ones in the right order.
+		 */
+		if (reader->cbuf_start == device->cbuf_end)
+			reader->cbuf_start = (reader->cbuf_start + 1) % ROCCAT_CBUF_SIZE;
+	}
+
+	mutex_unlock(&device->cbuf_lock);
+	mutex_unlock(&device->readers_lock);
+
+	wake_up_interruptible(&device->wait);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(roccat_report_event);
+
+/*
+ * roccat_connect() - create a char device for special event output
+ * @class: the class thats used to create the device. Meant to hold device
+ * specific sysfs attributes.
+ * @hid: the hid device the char device should be connected to.
+ * @report_size: size of reports
+ *
+ * Return value is minor device number in Range [0, ROCCAT_MAX_DEVICES] on
+ * success, a negative error code on failure.
+ */
+int roccat_connect(const struct class *klass, struct hid_device *hid, int report_size)
+{
+	unsigned int minor;
+	struct roccat_device *device;
+	int temp;
+
+	device = kzalloc_obj(struct roccat_device);
+	if (!device)
+		return -ENOMEM;
+
+	mutex_lock(&devices_lock);
+
+	for (minor = 0; minor < ROCCAT_MAX_DEVICES; ++minor) {
+		if (devices[minor])
+			continue;
+		break;
+	}
+
+	if (minor < ROCCAT_MAX_DEVICES) {
+		devices[minor] = device;
+	} else {
+		mutex_unlock(&devices_lock);
+		kfree(device);
+		return -EINVAL;
+	}
+
+	device->dev = device_create(klass, &hid->dev,
+			MKDEV(roccat_major, minor), NULL,
+			"%s%s%d", "roccat", hid->driver->name, minor);
+
+	if (IS_ERR(device->dev)) {
+		devices[minor] = NULL;
+		mutex_unlock(&devices_lock);
+		temp = PTR_ERR(device->dev);
+		kfree(device);
+		return temp;
+	}
+
+	mutex_unlock(&devices_lock);
+
+	init_waitqueue_head(&device->wait);
+	INIT_LIST_HEAD(&device->readers);
+	mutex_init(&device->readers_lock);
+	mutex_init(&device->cbuf_lock);
+	device->minor = minor;
+	device->hid = hid;
+	device->exist = 1;
+	device->cbuf_end = 0;
+	device->report_size = report_size;
+
+	return minor;
+}
+EXPORT_SYMBOL_GPL(roccat_connect);
+
+/* roccat_disconnect() - remove char device from hid device
+ * @minor: the minor device number returned by roccat_connect()
+ */
+void roccat_disconnect(int minor)
+{
+	struct roccat_device *device;
+
+	mutex_lock(&devices_lock);
+	device = devices[minor];
+	mutex_unlock(&devices_lock);
+
+	device->exist = 0; /* TODO exist maybe not needed */
+
+	device_destroy(device->dev->class, MKDEV(roccat_major, minor));
+
+	mutex_lock(&devices_lock);
+	devices[minor] = NULL;
+	mutex_unlock(&devices_lock);
+
+	if (device->open) {
+		hid_hw_close(device->hid);
+		wake_up_interruptible(&device->wait);
+	} else {
+		roccat_free_device(device);
+	}
+}
+EXPORT_SYMBOL_GPL(roccat_disconnect);
+
+static long roccat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
+{
+	struct inode *inode = file_inode(file);
+	struct roccat_device *device;
+	unsigned int minor = iminor(inode);
+	long retval = 0;
+
+	mutex_lock(&devices_lock);
+
+	device = devices[minor];
+	if (!device) {
+		retval = -ENODEV;
+		goto out;
+	}
+
+	switch (cmd) {
+	case ROCCATIOCGREPSIZE:
+		if (put_user(device->report_size, (int __user *)arg))
+			retval = -EFAULT;
+		break;
+	default:
+		retval = -ENOTTY;
+	}
+out:
+	mutex_unlock(&devices_lock);
+	return retval;
+}
+
+static const struct file_operations roccat_ops = {
+	.owner = THIS_MODULE,
+	.read = roccat_read,
+	.poll = roccat_poll,
+	.open = roccat_open,
+	.release = roccat_release,
+	.llseek = noop_llseek,
+	.unlocked_ioctl = roccat_ioctl,
+};
+
+static int __init roccat_init(void)
+{
+	int retval;
+	dev_t dev_id;
+
+	retval = alloc_chrdev_region(&dev_id, ROCCAT_FIRST_MINOR,
+			ROCCAT_MAX_DEVICES, "roccat");
+	if (retval < 0) {
+		pr_warn("can't get major number\n");
+		goto error;
+	}
+
+	roccat_major = MAJOR(dev_id);
+
+	cdev_init(&roccat_cdev, &roccat_ops);
+	retval = cdev_add(&roccat_cdev, dev_id, ROCCAT_MAX_DEVICES);
+
+	if (retval < 0) {
+		pr_warn("cannot add cdev\n");
+		goto cleanup_alloc_chrdev_region;
+	}
+	return 0;
+
+
+ cleanup_alloc_chrdev_region:
+	unregister_chrdev_region(dev_id, ROCCAT_MAX_DEVICES);
+ error:
+	return retval;
+}
+
+static void __exit roccat_exit(void)
+{
+	dev_t dev_id = MKDEV(roccat_major, 0);
+
+	cdev_del(&roccat_cdev);
+	unregister_chrdev_region(dev_id, ROCCAT_MAX_DEVICES);
+}
+
+module_init(roccat_init);
+module_exit(roccat_exit);
+
+MODULE_AUTHOR("Stefan Achatz");
+MODULE_DESCRIPTION("USB Roccat char device");
+MODULE_LICENSE("GPL v2");