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, 258 insertions, 0 deletions

diff --git a/drivers/mfd/max8925-i2c.c b/drivers/mfd/max8925-i2c.c
new file mode 100644
index 000000000..ab19ff0c7
--- /dev/null
+++ b/drivers/mfd/max8925-i2c.c
@@ -0,0 +1,258 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * I2C driver for Maxim MAX8925
+ *
+ * Copyright (C) 2009 Marvell International Ltd.
+ *	Haojian Zhuang <haojian.zhuang@marvell.com>
+ */
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/platform_device.h>
+#include <linux/i2c.h>
+#include <linux/mfd/max8925.h>
+#include <linux/slab.h>
+
+#define RTC_I2C_ADDR		0x68
+#define ADC_I2C_ADDR		0x47
+
+static inline int max8925_read_device(struct i2c_client *i2c,
+				      int reg, int bytes, void *dest)
+{
+	int ret;
+
+	if (bytes > 1)
+		ret = i2c_smbus_read_i2c_block_data(i2c, reg, bytes, dest);
+	else {
+		ret = i2c_smbus_read_byte_data(i2c, reg);
+		if (ret < 0)
+			return ret;
+		*(unsigned char *)dest = (unsigned char)ret;
+	}
+	return ret;
+}
+
+static inline int max8925_write_device(struct i2c_client *i2c,
+				       int reg, int bytes, void *src)
+{
+	unsigned char buf[9];
+	int ret;
+
+	buf[0] = (unsigned char)reg;
+	memcpy(&buf[1], src, bytes);
+
+	ret = i2c_master_send(i2c, buf, bytes + 1);
+	if (ret < 0)
+		return ret;
+	return 0;
+}
+
+int max8925_reg_read(struct i2c_client *i2c, int reg)
+{
+	struct max8925_chip *chip = i2c_get_clientdata(i2c);
+	unsigned char data = 0;
+	int ret;
+
+	mutex_lock(&chip->io_lock);
+	ret = max8925_read_device(i2c, reg, 1, &data);
+	mutex_unlock(&chip->io_lock);
+
+	if (ret < 0)
+		return ret;
+	else
+		return (int)data;
+}
+EXPORT_SYMBOL(max8925_reg_read);
+
+int max8925_reg_write(struct i2c_client *i2c, int reg,
+		unsigned char data)
+{
+	struct max8925_chip *chip = i2c_get_clientdata(i2c);
+	int ret;
+
+	mutex_lock(&chip->io_lock);
+	ret = max8925_write_device(i2c, reg, 1, &data);
+	mutex_unlock(&chip->io_lock);
+
+	return ret;
+}
+EXPORT_SYMBOL(max8925_reg_write);
+
+int max8925_bulk_read(struct i2c_client *i2c, int reg,
+		int count, unsigned char *buf)
+{
+	struct max8925_chip *chip = i2c_get_clientdata(i2c);
+	int ret;
+
+	mutex_lock(&chip->io_lock);
+	ret = max8925_read_device(i2c, reg, count, buf);
+	mutex_unlock(&chip->io_lock);
+
+	return ret;
+}
+EXPORT_SYMBOL(max8925_bulk_read);
+
+int max8925_bulk_write(struct i2c_client *i2c, int reg,
+		int count, unsigned char *buf)
+{
+	struct max8925_chip *chip = i2c_get_clientdata(i2c);
+	int ret;
+
+	mutex_lock(&chip->io_lock);
+	ret = max8925_write_device(i2c, reg, count, buf);
+	mutex_unlock(&chip->io_lock);
+
+	return ret;
+}
+EXPORT_SYMBOL(max8925_bulk_write);
+
+int max8925_set_bits(struct i2c_client *i2c, int reg,
+		unsigned char mask, unsigned char data)
+{
+	struct max8925_chip *chip = i2c_get_clientdata(i2c);
+	unsigned char value;
+	int ret;
+
+	mutex_lock(&chip->io_lock);
+	ret = max8925_read_device(i2c, reg, 1, &value);
+	if (ret < 0)
+		goto out;
+	value &= ~mask;
+	value |= data;
+	ret = max8925_write_device(i2c, reg, 1, &value);
+out:
+	mutex_unlock(&chip->io_lock);
+	return ret;
+}
+EXPORT_SYMBOL(max8925_set_bits);
+
+
+static const struct i2c_device_id max8925_id_table[] = {
+	{ "max8925" },
+	{ }
+};
+
+static int max8925_dt_init(struct device_node *np, struct device *dev,
+			   struct max8925_platform_data *pdata)
+{
+	int ret;
+
+	ret = of_property_read_u32(np, "maxim,tsc-irq", &pdata->tsc_irq);
+	if (ret) {
+		dev_err(dev, "Not found maxim,tsc-irq property\n");
+		return -EINVAL;
+	}
+	return 0;
+}
+
+static int max8925_probe(struct i2c_client *client)
+{
+	struct max8925_platform_data *pdata = dev_get_platdata(&client->dev);
+	struct max8925_chip *chip;
+	struct device_node *node = client->dev.of_node;
+
+	if (node && !pdata) {
+		/* parse DT to get platform data */
+		pdata = devm_kzalloc(&client->dev,
+				     sizeof(struct max8925_platform_data),
+				     GFP_KERNEL);
+		if (!pdata)
+			return -ENOMEM;
+
+		if (max8925_dt_init(node, &client->dev, pdata))
+			return -EINVAL;
+	} else if (!pdata) {
+		pr_info("%s: platform data is missing\n", __func__);
+		return -EINVAL;
+	}
+
+	chip = devm_kzalloc(&client->dev,
+			    sizeof(struct max8925_chip), GFP_KERNEL);
+	if (chip == NULL)
+		return -ENOMEM;
+	chip->i2c = client;
+	chip->dev = &client->dev;
+	i2c_set_clientdata(client, chip);
+	mutex_init(&chip->io_lock);
+
+	chip->rtc = i2c_new_dummy_device(chip->i2c->adapter, RTC_I2C_ADDR);
+	if (IS_ERR(chip->rtc)) {
+		dev_err(chip->dev, "Failed to allocate I2C device for RTC\n");
+		return PTR_ERR(chip->rtc);
+	}
+	i2c_set_clientdata(chip->rtc, chip);
+
+	chip->adc = i2c_new_dummy_device(chip->i2c->adapter, ADC_I2C_ADDR);
+	if (IS_ERR(chip->adc)) {
+		dev_err(chip->dev, "Failed to allocate I2C device for ADC\n");
+		i2c_unregister_device(chip->rtc);
+		return PTR_ERR(chip->adc);
+	}
+	i2c_set_clientdata(chip->adc, chip);
+
+	device_init_wakeup(&client->dev, 1);
+
+	max8925_device_init(chip, pdata);
+
+	return 0;
+}
+
+static void max8925_remove(struct i2c_client *client)
+{
+	struct max8925_chip *chip = i2c_get_clientdata(client);
+
+	max8925_device_exit(chip);
+	device_init_wakeup(&client->dev, false);
+	i2c_unregister_device(chip->adc);
+	i2c_unregister_device(chip->rtc);
+}
+
+static int max8925_suspend(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct max8925_chip *chip = i2c_get_clientdata(client);
+
+	if (device_may_wakeup(dev) && chip->wakeup_flag)
+		enable_irq_wake(chip->core_irq);
+	return 0;
+}
+
+static int max8925_resume(struct device *dev)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct max8925_chip *chip = i2c_get_clientdata(client);
+
+	if (device_may_wakeup(dev) && chip->wakeup_flag)
+		disable_irq_wake(chip->core_irq);
+	return 0;
+}
+
+static DEFINE_SIMPLE_DEV_PM_OPS(max8925_pm_ops,
+				max8925_suspend, max8925_resume);
+
+static const struct of_device_id max8925_dt_ids[] = {
+	{ .compatible = "maxim,max8925", },
+	{},
+};
+
+static struct i2c_driver max8925_driver = {
+	.driver	= {
+		.name	= "max8925",
+		.pm     = pm_sleep_ptr(&max8925_pm_ops),
+		.of_match_table = max8925_dt_ids,
+	},
+	.probe		= max8925_probe,
+	.remove		= max8925_remove,
+	.id_table	= max8925_id_table,
+};
+
+static int __init max8925_i2c_init(void)
+{
+	int ret;
+
+	ret = i2c_add_driver(&max8925_driver);
+	if (ret != 0)
+		pr_err("Failed to register MAX8925 I2C driver: %d\n", ret);
+
+	return ret;
+}
+subsys_initcall(max8925_i2c_init);