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, 144 insertions, 0 deletions

diff --git a/drivers/hwmon/ad7314.c b/drivers/hwmon/ad7314.c
new file mode 100644
index 000000000..59424103f
--- /dev/null
+++ b/drivers/hwmon/ad7314.c
@@ -0,0 +1,144 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * AD7314 digital temperature sensor driver for AD7314, ADT7301 and ADT7302
+ *
+ * Copyright 2010 Analog Devices Inc.
+ *
+ * Conversion to hwmon from IIO done by Jonathan Cameron <jic23@cam.ac.uk>
+ */
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/sysfs.h>
+#include <linux/spi/spi.h>
+#include <linux/module.h>
+#include <linux/err.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
+#include <linux/bitops.h>
+
+/*
+ * AD7314 temperature masks
+ */
+#define AD7314_TEMP_MASK		0x7FE0
+#define AD7314_TEMP_SHIFT		5
+#define AD7314_LEADING_ZEROS_MASK	BIT(15)
+
+/*
+ * ADT7301 and ADT7302 temperature masks
+ */
+#define ADT7301_TEMP_MASK		0x3FFF
+#define ADT7301_LEADING_ZEROS_MASK	(BIT(15) | BIT(14))
+
+enum ad7314_variant {
+	adt7301,
+	adt7302,
+	ad7314,
+};
+
+struct ad7314_data {
+	struct spi_device	*spi_dev;
+	u16 rx ____cacheline_aligned;
+};
+
+static int ad7314_spi_read(struct ad7314_data *chip)
+{
+	int ret;
+
+	ret = spi_read(chip->spi_dev, (u8 *)&chip->rx, sizeof(chip->rx));
+	if (ret < 0) {
+		dev_err(&chip->spi_dev->dev, "SPI read error\n");
+		return ret;
+	}
+
+	return be16_to_cpu(chip->rx);
+}
+
+static ssize_t ad7314_temperature_show(struct device *dev,
+				       struct device_attribute *attr,
+				       char *buf)
+{
+	struct ad7314_data *chip = dev_get_drvdata(dev);
+	s16 data;
+	int ret;
+
+	ret = ad7314_spi_read(chip);
+	if (ret < 0)
+		return ret;
+	switch (spi_get_device_id(chip->spi_dev)->driver_data) {
+	case ad7314:
+		if (ret & AD7314_LEADING_ZEROS_MASK) {
+			/* Invalid read-out, leading zero part is missing */
+			return -EIO;
+		}
+		data = (ret & AD7314_TEMP_MASK) >> AD7314_TEMP_SHIFT;
+		data = sign_extend32(data, 9);
+
+		return sprintf(buf, "%d\n", 250 * data);
+	case adt7301:
+	case adt7302:
+		if (ret & ADT7301_LEADING_ZEROS_MASK) {
+			/* Invalid read-out, leading zero part is missing */
+			return -EIO;
+		}
+		/*
+		 * Documented as a 13 bit twos complement register
+		 * with a sign bit - which is a 14 bit 2's complement
+		 * register.  1lsb - 31.25 milli degrees centigrade
+		 */
+		data = ret & ADT7301_TEMP_MASK;
+		data = sign_extend32(data, 13);
+
+		return sprintf(buf, "%d\n",
+			       DIV_ROUND_CLOSEST(data * 3125, 100));
+	default:
+		return -EINVAL;
+	}
+}
+
+static SENSOR_DEVICE_ATTR_RO(temp1_input, ad7314_temperature, 0);
+
+static struct attribute *ad7314_attrs[] = {
+	&sensor_dev_attr_temp1_input.dev_attr.attr,
+	NULL,
+};
+
+ATTRIBUTE_GROUPS(ad7314);
+
+static int ad7314_probe(struct spi_device *spi_dev)
+{
+	struct ad7314_data *chip;
+	struct device *hwmon_dev;
+
+	chip = devm_kzalloc(&spi_dev->dev, sizeof(*chip), GFP_KERNEL);
+	if (chip == NULL)
+		return -ENOMEM;
+
+	chip->spi_dev = spi_dev;
+	hwmon_dev = devm_hwmon_device_register_with_groups(&spi_dev->dev,
+							   spi_dev->modalias,
+							   chip, ad7314_groups);
+	return PTR_ERR_OR_ZERO(hwmon_dev);
+}
+
+static const struct spi_device_id ad7314_id[] = {
+	{ "adt7301", adt7301 },
+	{ "adt7302", adt7302 },
+	{ "ad7314", ad7314 },
+	{ }
+};
+MODULE_DEVICE_TABLE(spi, ad7314_id);
+
+static struct spi_driver ad7314_driver = {
+	.driver = {
+		.name = "ad7314",
+	},
+	.probe = ad7314_probe,
+	.id_table = ad7314_id,
+};
+
+module_spi_driver(ad7314_driver);
+
+MODULE_AUTHOR("Sonic Zhang <sonic.zhang@analog.com>");
+MODULE_DESCRIPTION("Analog Devices AD7314, ADT7301 and ADT7302 digital temperature sensor driver");
+MODULE_LICENSE("GPL v2");