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, 177 insertions, 0 deletions

diff --git a/drivers/gpio/gpio-moxtet.c b/drivers/gpio/gpio-moxtet.c
new file mode 100644
index 000000000..4eb9f1a27
--- /dev/null
+++ b/drivers/gpio/gpio-moxtet.c
@@ -0,0 +1,177 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *  Turris Mox Moxtet GPIO expander
+ *
+ *  Copyright (C) 2018 Marek Behún <kabel@kernel.org>
+ */
+
+#include <linux/bitops.h>
+#include <linux/gpio/driver.h>
+#include <linux/moxtet.h>
+#include <linux/module.h>
+
+#define MOXTET_GPIO_NGPIOS	12
+#define MOXTET_GPIO_INPUTS	4
+
+struct moxtet_gpio_desc {
+	u16 in_mask;
+	u16 out_mask;
+};
+
+static const struct moxtet_gpio_desc descs[] = {
+	[TURRIS_MOX_MODULE_SFP] = {
+		.in_mask = GENMASK(2, 0),
+		.out_mask = GENMASK(5, 4),
+	},
+};
+
+struct moxtet_gpio_chip {
+	struct device			*dev;
+	struct gpio_chip		gpio_chip;
+	const struct moxtet_gpio_desc	*desc;
+};
+
+static int moxtet_gpio_get_value(struct gpio_chip *gc, unsigned int offset)
+{
+	struct moxtet_gpio_chip *chip = gpiochip_get_data(gc);
+	int ret;
+
+	if (chip->desc->in_mask & BIT(offset)) {
+		ret = moxtet_device_read(chip->dev);
+	} else if (chip->desc->out_mask & BIT(offset)) {
+		ret = moxtet_device_written(chip->dev);
+		if (ret >= 0)
+			ret <<= MOXTET_GPIO_INPUTS;
+	} else {
+		return -EINVAL;
+	}
+
+	if (ret < 0)
+		return ret;
+
+	return !!(ret & BIT(offset));
+}
+
+static int moxtet_gpio_set_value(struct gpio_chip *gc, unsigned int offset,
+				 int val)
+{
+	struct moxtet_gpio_chip *chip = gpiochip_get_data(gc);
+	int state;
+
+	state = moxtet_device_written(chip->dev);
+	if (state < 0)
+		return state;
+
+	offset -= MOXTET_GPIO_INPUTS;
+
+	if (val)
+		state |= BIT(offset);
+	else
+		state &= ~BIT(offset);
+
+	return moxtet_device_write(chip->dev, state);
+}
+
+static int moxtet_gpio_get_direction(struct gpio_chip *gc, unsigned int offset)
+{
+	struct moxtet_gpio_chip *chip = gpiochip_get_data(gc);
+
+	/* All lines are hard wired to be either input or output, not both. */
+	if (chip->desc->in_mask & BIT(offset))
+		return GPIO_LINE_DIRECTION_IN;
+	else if (chip->desc->out_mask & BIT(offset))
+		return GPIO_LINE_DIRECTION_OUT;
+	else
+		return -EINVAL;
+}
+
+static int moxtet_gpio_direction_input(struct gpio_chip *gc,
+				       unsigned int offset)
+{
+	struct moxtet_gpio_chip *chip = gpiochip_get_data(gc);
+
+	if (chip->desc->in_mask & BIT(offset))
+		return 0;
+	else if (chip->desc->out_mask & BIT(offset))
+		return -ENOTSUPP;
+	else
+		return -EINVAL;
+}
+
+static int moxtet_gpio_direction_output(struct gpio_chip *gc,
+					unsigned int offset, int val)
+{
+	struct moxtet_gpio_chip *chip = gpiochip_get_data(gc);
+
+	if (chip->desc->out_mask & BIT(offset))
+		return moxtet_gpio_set_value(gc, offset, val);
+	else if (chip->desc->in_mask & BIT(offset))
+		return -ENOTSUPP;
+
+	return -EINVAL;
+}
+
+static int moxtet_gpio_probe(struct device *dev)
+{
+	struct moxtet_gpio_chip *chip;
+	struct device_node *nc = dev->of_node;
+	int id;
+
+	id = to_moxtet_device(dev)->id;
+
+	if (id >= ARRAY_SIZE(descs)) {
+		dev_err(dev, "%pOF Moxtet device id 0x%x is not supported by gpio-moxtet driver\n",
+			nc, id);
+		return -ENOTSUPP;
+	}
+
+	chip = devm_kzalloc(dev, sizeof(*chip), GFP_KERNEL);
+	if (!chip)
+		return -ENOMEM;
+
+	chip->dev = dev;
+	chip->gpio_chip.parent = dev;
+	chip->desc = &descs[id];
+
+	dev_set_drvdata(dev, chip);
+
+	chip->gpio_chip.label = dev_name(dev);
+	chip->gpio_chip.get_direction = moxtet_gpio_get_direction;
+	chip->gpio_chip.direction_input = moxtet_gpio_direction_input;
+	chip->gpio_chip.direction_output = moxtet_gpio_direction_output;
+	chip->gpio_chip.get = moxtet_gpio_get_value;
+	chip->gpio_chip.set = moxtet_gpio_set_value;
+	chip->gpio_chip.base = -1;
+
+	chip->gpio_chip.ngpio = MOXTET_GPIO_NGPIOS;
+
+	chip->gpio_chip.can_sleep = true;
+	chip->gpio_chip.owner = THIS_MODULE;
+
+	return devm_gpiochip_add_data(dev, &chip->gpio_chip, chip);
+}
+
+static const struct of_device_id moxtet_gpio_dt_ids[] = {
+	{ .compatible = "cznic,moxtet-gpio", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, moxtet_gpio_dt_ids);
+
+static const enum turris_mox_module_id moxtet_gpio_module_table[] = {
+	TURRIS_MOX_MODULE_SFP,
+	0,
+};
+
+static struct moxtet_driver moxtet_gpio_driver = {
+	.driver = {
+		.name		= "moxtet-gpio",
+		.of_match_table	= moxtet_gpio_dt_ids,
+		.probe		= moxtet_gpio_probe,
+	},
+	.id_table = moxtet_gpio_module_table,
+};
+module_moxtet_driver(moxtet_gpio_driver);
+
+MODULE_AUTHOR("Marek Behun <kabel@kernel.org>");
+MODULE_DESCRIPTION("Turris Mox Moxtet GPIO expander");
+MODULE_LICENSE("GPL v2");