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, 155 insertions, 0 deletions

diff --git a/drivers/mfd/lp3943.c b/drivers/mfd/lp3943.c
new file mode 100644
index 000000000..1918b5c7a
--- /dev/null
+++ b/drivers/mfd/lp3943.c
@@ -0,0 +1,155 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * TI/National Semiconductor LP3943 MFD Core Driver
+ *
+ * Copyright 2013 Texas Instruments
+ *
+ * Author: Milo Kim <milo.kim@ti.com>
+ *
+ * Driver structure:
+ *   LP3943 is an integrated device capable of driving 16 output channels.
+ *   It can be used for a GPIO expander and PWM generators.
+ *
+ *                                   LED control    General usage for a device
+ *                                   ___________   ____________________________
+ *
+ *   LP3943 MFD ---- GPIO expander    leds-gpio        eg) HW enable pin
+ *               |
+ *               --- PWM generator    leds-pwm         eg) PWM input
+ *
+ *   Internal two PWM channels are used for LED dimming effect.
+ *   And each output pin can be used as a GPIO as well.
+ *   The LED functionality can work with GPIOs or PWMs.
+ *   LEDs can be controlled with legacy leds-gpio(static brightness) or
+ *   leds-pwm drivers(dynamic brightness control).
+ *   Alternatively, it can be used for generic GPIO and PWM controller.
+ *   For example, a GPIO is HW enable pin of a device.
+ *   A PWM is input pin of a backlight device.
+ */
+
+#include <linux/err.h>
+#include <linux/gpio/consumer.h>
+#include <linux/i2c.h>
+#include <linux/mfd/core.h>
+#include <linux/mfd/lp3943.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/slab.h>
+
+#define LP3943_MAX_REGISTERS		0x09
+
+/* Register configuration for pin MUX */
+static const struct lp3943_reg_cfg lp3943_mux_cfg[] = {
+	/* address, mask, shift */
+	{ LP3943_REG_MUX0, 0x03, 0 },
+	{ LP3943_REG_MUX0, 0x0C, 2 },
+	{ LP3943_REG_MUX0, 0x30, 4 },
+	{ LP3943_REG_MUX0, 0xC0, 6 },
+	{ LP3943_REG_MUX1, 0x03, 0 },
+	{ LP3943_REG_MUX1, 0x0C, 2 },
+	{ LP3943_REG_MUX1, 0x30, 4 },
+	{ LP3943_REG_MUX1, 0xC0, 6 },
+	{ LP3943_REG_MUX2, 0x03, 0 },
+	{ LP3943_REG_MUX2, 0x0C, 2 },
+	{ LP3943_REG_MUX2, 0x30, 4 },
+	{ LP3943_REG_MUX2, 0xC0, 6 },
+	{ LP3943_REG_MUX3, 0x03, 0 },
+	{ LP3943_REG_MUX3, 0x0C, 2 },
+	{ LP3943_REG_MUX3, 0x30, 4 },
+	{ LP3943_REG_MUX3, 0xC0, 6 },
+};
+
+static const struct mfd_cell lp3943_devs[] = {
+	{
+		.name = "lp3943-pwm",
+		.of_compatible = "ti,lp3943-pwm",
+	},
+	{
+		.name = "lp3943-gpio",
+		.of_compatible = "ti,lp3943-gpio",
+	},
+};
+
+int lp3943_read_byte(struct lp3943 *lp3943, u8 reg, u8 *read)
+{
+	int ret;
+	unsigned int val;
+
+	ret = regmap_read(lp3943->regmap, reg, &val);
+	if (ret < 0)
+		return ret;
+
+	*read = (u8)val;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(lp3943_read_byte);
+
+int lp3943_write_byte(struct lp3943 *lp3943, u8 reg, u8 data)
+{
+	return regmap_write(lp3943->regmap, reg, data);
+}
+EXPORT_SYMBOL_GPL(lp3943_write_byte);
+
+int lp3943_update_bits(struct lp3943 *lp3943, u8 reg, u8 mask, u8 data)
+{
+	return regmap_update_bits(lp3943->regmap, reg, mask, data);
+}
+EXPORT_SYMBOL_GPL(lp3943_update_bits);
+
+static const struct regmap_config lp3943_regmap_config = {
+	.reg_bits = 8,
+	.val_bits = 8,
+	.max_register = LP3943_MAX_REGISTERS,
+};
+
+static int lp3943_probe(struct i2c_client *cl)
+{
+	struct lp3943 *lp3943;
+	struct device *dev = &cl->dev;
+
+	lp3943 = devm_kzalloc(dev, sizeof(*lp3943), GFP_KERNEL);
+	if (!lp3943)
+		return -ENOMEM;
+
+	lp3943->regmap = devm_regmap_init_i2c(cl, &lp3943_regmap_config);
+	if (IS_ERR(lp3943->regmap))
+		return PTR_ERR(lp3943->regmap);
+
+	lp3943->pdata = dev_get_platdata(dev);
+	lp3943->dev = dev;
+	lp3943->mux_cfg = lp3943_mux_cfg;
+	i2c_set_clientdata(cl, lp3943);
+
+	return devm_mfd_add_devices(dev, -1, lp3943_devs,
+				    ARRAY_SIZE(lp3943_devs),
+				    NULL, 0, NULL);
+}
+
+static const struct i2c_device_id lp3943_ids[] = {
+	{ "lp3943" },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, lp3943_ids);
+
+#ifdef CONFIG_OF
+static const struct of_device_id lp3943_of_match[] = {
+	{ .compatible = "ti,lp3943", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, lp3943_of_match);
+#endif
+
+static struct i2c_driver lp3943_driver = {
+	.probe = lp3943_probe,
+	.driver = {
+		.name = "lp3943",
+		.of_match_table = of_match_ptr(lp3943_of_match),
+	},
+	.id_table = lp3943_ids,
+};
+
+module_i2c_driver(lp3943_driver);
+
+MODULE_DESCRIPTION("LP3943 MFD Core Driver");
+MODULE_AUTHOR("Milo Kim");
+MODULE_LICENSE("GPL");