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, 293 insertions, 0 deletions

diff --git a/drivers/hwmon/max1111.c b/drivers/hwmon/max1111.c
new file mode 100644
index 000000000..5cc08c720
--- /dev/null
+++ b/drivers/hwmon/max1111.c
@@ -0,0 +1,293 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * max1111.c - +2.7V, Low-Power, Multichannel, Serial 8-bit ADCs
+ *
+ * Based on arch/arm/mach-pxa/corgi_ssp.c
+ *
+ * Copyright (C) 2004-2005 Richard Purdie
+ *
+ * Copyright (C) 2008 Marvell International Ltd.
+ *	Eric Miao <eric.miao@marvell.com>
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/err.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
+#include <linux/spi/spi.h>
+#include <linux/slab.h>
+
+enum chips { max1110, max1111, max1112, max1113 };
+
+#define MAX1111_TX_BUF_SIZE	1
+#define MAX1111_RX_BUF_SIZE	2
+
+/* MAX1111 Commands */
+#define MAX1111_CTRL_PD0      (1u << 0)
+#define MAX1111_CTRL_PD1      (1u << 1)
+#define MAX1111_CTRL_SGL      (1u << 2)
+#define MAX1111_CTRL_UNI      (1u << 3)
+#define MAX1110_CTRL_SEL_SH   (4)
+#define MAX1111_CTRL_SEL_SH   (5)	/* NOTE: bit 4 is ignored */
+#define MAX1111_CTRL_STR      (1u << 7)
+
+struct max1111_data {
+	struct spi_device	*spi;
+	struct device		*hwmon_dev;
+	struct spi_message	msg;
+	struct spi_transfer	xfer[2];
+	uint8_t tx_buf[MAX1111_TX_BUF_SIZE];
+	uint8_t rx_buf[MAX1111_RX_BUF_SIZE];
+	struct mutex		drvdata_lock;
+	/* protect msg, xfer and buffers from multiple access */
+	int			sel_sh;
+	int			lsb;
+};
+
+static int max1111_read(struct device *dev, int channel)
+{
+	struct max1111_data *data = dev_get_drvdata(dev);
+	uint8_t v1, v2;
+	int err;
+
+	/* writing to drvdata struct is not thread safe, wait on mutex */
+	mutex_lock(&data->drvdata_lock);
+
+	data->tx_buf[0] = (channel << data->sel_sh) |
+		MAX1111_CTRL_PD0 | MAX1111_CTRL_PD1 |
+		MAX1111_CTRL_SGL | MAX1111_CTRL_UNI | MAX1111_CTRL_STR;
+
+	err = spi_sync(data->spi, &data->msg);
+	if (err < 0) {
+		dev_err(dev, "spi_sync failed with %d\n", err);
+		mutex_unlock(&data->drvdata_lock);
+		return err;
+	}
+
+	v1 = data->rx_buf[0];
+	v2 = data->rx_buf[1];
+
+	mutex_unlock(&data->drvdata_lock);
+
+	if ((v1 & 0xc0) || (v2 & 0x3f))
+		return -EINVAL;
+
+	return (v1 << 2) | (v2 >> 6);
+}
+
+#ifdef CONFIG_SHARPSL_PM
+static struct max1111_data *the_max1111;
+
+int max1111_read_channel(int channel);
+int max1111_read_channel(int channel)
+{
+	if (!the_max1111 || !the_max1111->spi)
+		return -ENODEV;
+
+	return max1111_read(&the_max1111->spi->dev, channel);
+}
+EXPORT_SYMBOL(max1111_read_channel);
+#endif
+
+/*
+ * NOTE: SPI devices do not have a default 'name' attribute, which is
+ * likely to be used by hwmon applications to distinguish between
+ * different devices, explicitly add a name attribute here.
+ */
+static ssize_t name_show(struct device *dev,
+			 struct device_attribute *attr, char *buf)
+{
+	return sprintf(buf, "%s\n", to_spi_device(dev)->modalias);
+}
+
+static ssize_t show_adc(struct device *dev,
+			struct device_attribute *attr, char *buf)
+{
+	struct max1111_data *data = dev_get_drvdata(dev);
+	int channel = to_sensor_dev_attr(attr)->index;
+	int ret;
+
+	ret = max1111_read(dev, channel);
+	if (ret < 0)
+		return ret;
+
+	/*
+	 * Assume the reference voltage to be 2.048V or 4.096V, with an 8-bit
+	 * sample. The LSB weight is 8mV or 16mV depending on the chip type.
+	 */
+	return sprintf(buf, "%d\n", ret * data->lsb);
+}
+
+#define MAX1111_ADC_ATTR(_id)		\
+	SENSOR_DEVICE_ATTR(in##_id##_input, S_IRUGO, show_adc, NULL, _id)
+
+static DEVICE_ATTR_RO(name);
+static MAX1111_ADC_ATTR(0);
+static MAX1111_ADC_ATTR(1);
+static MAX1111_ADC_ATTR(2);
+static MAX1111_ADC_ATTR(3);
+static MAX1111_ADC_ATTR(4);
+static MAX1111_ADC_ATTR(5);
+static MAX1111_ADC_ATTR(6);
+static MAX1111_ADC_ATTR(7);
+
+static struct attribute *max1111_attributes[] = {
+	&dev_attr_name.attr,
+	&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,
+	NULL,
+};
+
+static const struct attribute_group max1111_attr_group = {
+	.attrs	= max1111_attributes,
+};
+
+static struct attribute *max1110_attributes[] = {
+	&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,
+};
+
+static const struct attribute_group max1110_attr_group = {
+	.attrs	= max1110_attributes,
+};
+
+static int setup_transfer(struct max1111_data *data)
+{
+	struct spi_message *m;
+	struct spi_transfer *x;
+
+	m = &data->msg;
+	x = &data->xfer[0];
+
+	spi_message_init(m);
+
+	x->tx_buf = &data->tx_buf[0];
+	x->len = MAX1111_TX_BUF_SIZE;
+	spi_message_add_tail(x, m);
+
+	x++;
+	x->rx_buf = &data->rx_buf[0];
+	x->len = MAX1111_RX_BUF_SIZE;
+	spi_message_add_tail(x, m);
+
+	return 0;
+}
+
+static int max1111_probe(struct spi_device *spi)
+{
+	enum chips chip = spi_get_device_id(spi)->driver_data;
+	struct max1111_data *data;
+	int err;
+
+	spi->bits_per_word = 8;
+	spi->mode = SPI_MODE_0;
+	err = spi_setup(spi);
+	if (err < 0)
+		return err;
+
+	data = devm_kzalloc(&spi->dev, sizeof(struct max1111_data), GFP_KERNEL);
+	if (data == NULL)
+		return -ENOMEM;
+
+	switch (chip) {
+	case max1110:
+		data->lsb = 8;
+		data->sel_sh = MAX1110_CTRL_SEL_SH;
+		break;
+	case max1111:
+		data->lsb = 8;
+		data->sel_sh = MAX1111_CTRL_SEL_SH;
+		break;
+	case max1112:
+		data->lsb = 16;
+		data->sel_sh = MAX1110_CTRL_SEL_SH;
+		break;
+	case max1113:
+		data->lsb = 16;
+		data->sel_sh = MAX1111_CTRL_SEL_SH;
+		break;
+	}
+	err = setup_transfer(data);
+	if (err)
+		return err;
+
+	mutex_init(&data->drvdata_lock);
+
+	data->spi = spi;
+	spi_set_drvdata(spi, data);
+
+	err = sysfs_create_group(&spi->dev.kobj, &max1111_attr_group);
+	if (err) {
+		dev_err(&spi->dev, "failed to create attribute group\n");
+		return err;
+	}
+	if (chip == max1110 || chip == max1112) {
+		err = sysfs_create_group(&spi->dev.kobj, &max1110_attr_group);
+		if (err) {
+			dev_err(&spi->dev,
+				"failed to create extended attribute group\n");
+			goto err_remove;
+		}
+	}
+
+	data->hwmon_dev = hwmon_device_register(&spi->dev);
+	if (IS_ERR(data->hwmon_dev)) {
+		dev_err(&spi->dev, "failed to create hwmon device\n");
+		err = PTR_ERR(data->hwmon_dev);
+		goto err_remove;
+	}
+
+#ifdef CONFIG_SHARPSL_PM
+	the_max1111 = data;
+#endif
+	return 0;
+
+err_remove:
+	sysfs_remove_group(&spi->dev.kobj, &max1110_attr_group);
+	sysfs_remove_group(&spi->dev.kobj, &max1111_attr_group);
+	return err;
+}
+
+static void max1111_remove(struct spi_device *spi)
+{
+	struct max1111_data *data = spi_get_drvdata(spi);
+
+#ifdef CONFIG_SHARPSL_PM
+	the_max1111 = NULL;
+#endif
+	hwmon_device_unregister(data->hwmon_dev);
+	sysfs_remove_group(&spi->dev.kobj, &max1110_attr_group);
+	sysfs_remove_group(&spi->dev.kobj, &max1111_attr_group);
+	mutex_destroy(&data->drvdata_lock);
+}
+
+static const struct spi_device_id max1111_ids[] = {
+	{ "max1110", max1110 },
+	{ "max1111", max1111 },
+	{ "max1112", max1112 },
+	{ "max1113", max1113 },
+	{ },
+};
+MODULE_DEVICE_TABLE(spi, max1111_ids);
+
+static struct spi_driver max1111_driver = {
+	.driver		= {
+		.name	= "max1111",
+	},
+	.id_table	= max1111_ids,
+	.probe		= max1111_probe,
+	.remove		= max1111_remove,
+};
+
+module_spi_driver(max1111_driver);
+
+MODULE_AUTHOR("Eric Miao <eric.miao@marvell.com>");
+MODULE_DESCRIPTION("MAX1110/MAX1111/MAX1112/MAX1113 ADC Driver");
+MODULE_LICENSE("GPL");