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, 213 insertions, 0 deletions

diff --git a/drivers/hwmon/ads7828.c b/drivers/hwmon/ads7828.c
new file mode 100644
index 000000000..f8f2f621d
--- /dev/null
+++ b/drivers/hwmon/ads7828.c
@@ -0,0 +1,213 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * ads7828.c - driver for TI ADS7828 8-channel A/D converter and compatibles
+ * (C) 2007 EADS Astrium
+ *
+ * This driver is based on the lm75 and other lm_sensors/hwmon drivers
+ *
+ * Written by Steve Hardy <shardy@redhat.com>
+ *
+ * ADS7830 support, by Guillaume Roguez <guillaume.roguez@savoirfairelinux.com>
+ *
+ * For further information, see the Documentation/hwmon/ads7828.rst file.
+ */
+
+#include <linux/err.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_data/ads7828.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+#include <linux/regulator/consumer.h>
+
+/* The ADS7828 registers */
+#define ADS7828_CMD_SD_SE	0x80	/* Single ended inputs */
+#define ADS7828_CMD_PD1		0x04	/* Internal vref OFF && A/D ON */
+#define ADS7828_CMD_PD3		0x0C	/* Internal vref ON && A/D ON */
+#define ADS7828_INT_VREF_MV	2500	/* Internal vref is 2.5V, 2500mV */
+#define ADS7828_EXT_VREF_MV_MIN	50	/* External vref min value 0.05V */
+#define ADS7828_EXT_VREF_MV_MAX	5250	/* External vref max value 5.25V */
+
+/* List of supported devices */
+enum ads7828_chips { ads7828, ads7830 };
+
+/* Client specific data */
+struct ads7828_data {
+	struct regmap *regmap;
+	u8 cmd_byte;			/* Command byte without channel bits */
+	unsigned int lsb_resol;		/* Resolution of the ADC sample LSB */
+};
+
+/* Command byte C2,C1,C0 - see datasheet */
+static inline u8 ads7828_cmd_byte(u8 cmd, int ch)
+{
+	return cmd | (((ch >> 1) | (ch & 0x01) << 2) << 4);
+}
+
+/* sysfs callback function */
+static ssize_t ads7828_in_show(struct device *dev,
+			       struct device_attribute *da, char *buf)
+{
+	struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
+	struct ads7828_data *data = dev_get_drvdata(dev);
+	u8 cmd = ads7828_cmd_byte(data->cmd_byte, attr->index);
+	unsigned int regval;
+	int err;
+
+	err = regmap_read(data->regmap, cmd, &regval);
+	if (err < 0)
+		return err;
+
+	return sysfs_emit(buf, "%d\n",
+			  DIV_ROUND_CLOSEST(regval * data->lsb_resol, 1000));
+}
+
+static SENSOR_DEVICE_ATTR_RO(in0_input, ads7828_in, 0);
+static SENSOR_DEVICE_ATTR_RO(in1_input, ads7828_in, 1);
+static SENSOR_DEVICE_ATTR_RO(in2_input, ads7828_in, 2);
+static SENSOR_DEVICE_ATTR_RO(in3_input, ads7828_in, 3);
+static SENSOR_DEVICE_ATTR_RO(in4_input, ads7828_in, 4);
+static SENSOR_DEVICE_ATTR_RO(in5_input, ads7828_in, 5);
+static SENSOR_DEVICE_ATTR_RO(in6_input, ads7828_in, 6);
+static SENSOR_DEVICE_ATTR_RO(in7_input, ads7828_in, 7);
+
+static struct attribute *ads7828_attrs[] = {
+	&sensor_dev_attr_in0_input.dev_attr.attr,
+	&sensor_dev_attr_in1_input.dev_attr.attr,
+	&sensor_dev_attr_in2_input.dev_attr.attr,
+	&sensor_dev_attr_in3_input.dev_attr.attr,
+	&sensor_dev_attr_in4_input.dev_attr.attr,
+	&sensor_dev_attr_in5_input.dev_attr.attr,
+	&sensor_dev_attr_in6_input.dev_attr.attr,
+	&sensor_dev_attr_in7_input.dev_attr.attr,
+	NULL
+};
+
+ATTRIBUTE_GROUPS(ads7828);
+
+static const struct regmap_config ads2828_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 16,
+};
+
+static const struct regmap_config ads2830_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+};
+
+static int ads7828_probe(struct i2c_client *client)
+{
+	struct device *dev = &client->dev;
+	struct ads7828_platform_data *pdata = dev_get_platdata(dev);
+	struct ads7828_data *data;
+	struct device *hwmon_dev;
+	unsigned int vref_mv = ADS7828_INT_VREF_MV;
+	int vref_uv;
+	bool diff_input = false;
+	bool ext_vref = false;
+	unsigned int regval;
+	enum ads7828_chips chip;
+
+	data = devm_kzalloc(dev, sizeof(struct ads7828_data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	if (pdata) {
+		diff_input = pdata->diff_input;
+		ext_vref = pdata->ext_vref;
+		if (ext_vref && pdata->vref_mv)
+			vref_mv = pdata->vref_mv;
+	} else if (dev->of_node) {
+		diff_input = of_property_read_bool(dev->of_node,
+						   "ti,differential-input");
+		vref_uv = devm_regulator_get_enable_read_voltage(dev, "vref");
+		if (vref_uv < 0) {
+			if (vref_uv != -ENODEV)
+				return vref_uv;
+		} else {
+			vref_mv = DIV_ROUND_CLOSEST(vref_uv, 1000);
+			if (vref_mv < ADS7828_EXT_VREF_MV_MIN ||
+			    vref_mv > ADS7828_EXT_VREF_MV_MAX)
+				return -EINVAL;
+			ext_vref = true;
+		}
+	}
+
+	chip = (uintptr_t)i2c_get_match_data(client);
+
+	/* Bound Vref with min/max values */
+	vref_mv = clamp_val(vref_mv, ADS7828_EXT_VREF_MV_MIN,
+			    ADS7828_EXT_VREF_MV_MAX);
+
+	/* ADS7828 uses 12-bit samples, while ADS7830 is 8-bit */
+	if (chip == ads7828) {
+		data->lsb_resol = DIV_ROUND_CLOSEST(vref_mv * 1000, 4096);
+		data->regmap = devm_regmap_init_i2c(client,
+						    &ads2828_regmap_config);
+	} else {
+		data->lsb_resol = DIV_ROUND_CLOSEST(vref_mv * 1000, 256);
+		data->regmap = devm_regmap_init_i2c(client,
+						    &ads2830_regmap_config);
+	}
+
+	if (IS_ERR(data->regmap))
+		return PTR_ERR(data->regmap);
+
+	data->cmd_byte = ext_vref ? ADS7828_CMD_PD1 : ADS7828_CMD_PD3;
+	if (!diff_input)
+		data->cmd_byte |= ADS7828_CMD_SD_SE;
+
+	/*
+	 * Datasheet specifies internal reference voltage is disabled by
+	 * default. The internal reference voltage needs to be enabled and
+	 * voltage needs to settle before getting valid ADC data. So perform a
+	 * dummy read to enable the internal reference voltage.
+	 */
+	if (!ext_vref)
+		regmap_read(data->regmap, data->cmd_byte, &regval);
+
+	hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,
+							   data,
+							   ads7828_groups);
+	return PTR_ERR_OR_ZERO(hwmon_dev);
+}
+
+static const struct i2c_device_id ads7828_device_ids[] = {
+	{ .name = "ads7828", .driver_data = ads7828 },
+	{ .name = "ads7830", .driver_data = ads7830 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, ads7828_device_ids);
+
+static const struct of_device_id __maybe_unused ads7828_of_match[] = {
+	{
+		.compatible = "ti,ads7828",
+		.data = (void *)ads7828
+	},
+	{
+		.compatible = "ti,ads7830",
+		.data = (void *)ads7830
+	},
+	{ },
+};
+MODULE_DEVICE_TABLE(of, ads7828_of_match);
+
+static struct i2c_driver ads7828_driver = {
+	.driver = {
+		.name = "ads7828",
+		.of_match_table = of_match_ptr(ads7828_of_match),
+	},
+
+	.id_table = ads7828_device_ids,
+	.probe = ads7828_probe,
+};
+
+module_i2c_driver(ads7828_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Steve Hardy <shardy@redhat.com>");
+MODULE_DESCRIPTION("Driver for TI ADS7828 A/D converter and compatibles");