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, 271 insertions, 0 deletions

diff --git a/drivers/gpio/gpio-siox.c b/drivers/gpio/gpio-siox.c
new file mode 100644
index 000000000..958034b9f
--- /dev/null
+++ b/drivers/gpio/gpio-siox.c
@@ -0,0 +1,271 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2015-2018 Pengutronix, Uwe Kleine-König <kernel@pengutronix.de>
+ */
+
+#include <linux/module.h>
+#include <linux/siox.h>
+#include <linux/gpio/driver.h>
+#include <linux/of.h>
+
+struct gpio_siox_ddata {
+	struct gpio_chip gchip;
+	struct mutex lock;
+	u8 setdata[1];
+	u8 getdata[3];
+
+	raw_spinlock_t irqlock;
+	u32 irq_enable;
+	u32 irq_status;
+	u32 irq_type[20];
+};
+
+/*
+ * Note that this callback only sets the value that is clocked out in the next
+ * cycle.
+ */
+static int gpio_siox_set_data(struct siox_device *sdevice, u8 status, u8 buf[])
+{
+	struct gpio_siox_ddata *ddata = dev_get_drvdata(&sdevice->dev);
+
+	mutex_lock(&ddata->lock);
+	buf[0] = ddata->setdata[0];
+	mutex_unlock(&ddata->lock);
+
+	return 0;
+}
+
+static int gpio_siox_get_data(struct siox_device *sdevice, const u8 buf[])
+{
+	struct gpio_siox_ddata *ddata = dev_get_drvdata(&sdevice->dev);
+	size_t offset;
+	u32 trigger;
+
+	mutex_lock(&ddata->lock);
+
+	raw_spin_lock_irq(&ddata->irqlock);
+
+	for (offset = 0; offset < 12; ++offset) {
+		unsigned int bitpos = 11 - offset;
+		unsigned int gpiolevel = buf[bitpos / 8] & (1 << bitpos % 8);
+		unsigned int prev_level =
+			ddata->getdata[bitpos / 8] & (1 << (bitpos % 8));
+		u32 irq_type = ddata->irq_type[offset];
+
+		if (gpiolevel) {
+			if ((irq_type & IRQ_TYPE_LEVEL_HIGH) ||
+			    ((irq_type & IRQ_TYPE_EDGE_RISING) && !prev_level))
+				ddata->irq_status |= 1 << offset;
+		} else {
+			if ((irq_type & IRQ_TYPE_LEVEL_LOW) ||
+			    ((irq_type & IRQ_TYPE_EDGE_FALLING) && prev_level))
+				ddata->irq_status |= 1 << offset;
+		}
+	}
+
+	trigger = ddata->irq_status & ddata->irq_enable;
+
+	raw_spin_unlock_irq(&ddata->irqlock);
+
+	ddata->getdata[0] = buf[0];
+	ddata->getdata[1] = buf[1];
+	ddata->getdata[2] = buf[2];
+
+	mutex_unlock(&ddata->lock);
+
+	for (offset = 0; offset < 12; ++offset) {
+		if (trigger & (1 << offset)) {
+			struct irq_domain *irqdomain = ddata->gchip.irq.domain;
+			unsigned int irq = irq_find_mapping(irqdomain, offset);
+
+			/*
+			 * Conceptually handle_nested_irq should call the flow
+			 * handler of the irq chip. But it doesn't, so we have
+			 * to clean the irq_status here.
+			 */
+			raw_spin_lock_irq(&ddata->irqlock);
+			ddata->irq_status &= ~(1 << offset);
+			raw_spin_unlock_irq(&ddata->irqlock);
+
+			handle_nested_irq(irq);
+		}
+	}
+
+	return 0;
+}
+
+static void gpio_siox_irq_ack(struct irq_data *d)
+{
+	struct gpio_chip *gc = irq_data_get_irq_chip_data(d);
+	struct gpio_siox_ddata *ddata = gpiochip_get_data(gc);
+
+	raw_spin_lock(&ddata->irqlock);
+	ddata->irq_status &= ~(1 << d->hwirq);
+	raw_spin_unlock(&ddata->irqlock);
+}
+
+static void gpio_siox_irq_mask(struct irq_data *d)
+{
+	struct gpio_chip *gc = irq_data_get_irq_chip_data(d);
+	struct gpio_siox_ddata *ddata = gpiochip_get_data(gc);
+
+	raw_spin_lock(&ddata->irqlock);
+	ddata->irq_enable &= ~(1 << d->hwirq);
+	raw_spin_unlock(&ddata->irqlock);
+	gpiochip_disable_irq(gc, irqd_to_hwirq(d));
+}
+
+static void gpio_siox_irq_unmask(struct irq_data *d)
+{
+	struct gpio_chip *gc = irq_data_get_irq_chip_data(d);
+	struct gpio_siox_ddata *ddata = gpiochip_get_data(gc);
+
+	gpiochip_enable_irq(gc, irqd_to_hwirq(d));
+	raw_spin_lock(&ddata->irqlock);
+	ddata->irq_enable |= 1 << d->hwirq;
+	raw_spin_unlock(&ddata->irqlock);
+}
+
+static int gpio_siox_irq_set_type(struct irq_data *d, u32 type)
+{
+	struct gpio_chip *gc = irq_data_get_irq_chip_data(d);
+	struct gpio_siox_ddata *ddata = gpiochip_get_data(gc);
+
+	raw_spin_lock(&ddata->irqlock);
+	ddata->irq_type[d->hwirq] = type;
+	raw_spin_unlock(&ddata->irqlock);
+
+	return 0;
+}
+
+static int gpio_siox_get(struct gpio_chip *chip, unsigned int offset)
+{
+	struct gpio_siox_ddata *ddata = gpiochip_get_data(chip);
+	int ret;
+
+	mutex_lock(&ddata->lock);
+
+	if (offset >= 12) {
+		unsigned int bitpos = 19 - offset;
+
+		ret = ddata->setdata[0] & (1 << bitpos);
+	} else {
+		unsigned int bitpos = 11 - offset;
+
+		ret = ddata->getdata[bitpos / 8] & (1 << (bitpos % 8));
+	}
+
+	mutex_unlock(&ddata->lock);
+
+	return ret;
+}
+
+static int gpio_siox_set(struct gpio_chip *chip,
+			 unsigned int offset, int value)
+{
+	struct gpio_siox_ddata *ddata = gpiochip_get_data(chip);
+	u8 mask = 1 << (19 - offset);
+
+	mutex_lock(&ddata->lock);
+
+	if (value)
+		ddata->setdata[0] |= mask;
+	else
+		ddata->setdata[0] &= ~mask;
+
+	mutex_unlock(&ddata->lock);
+
+	return 0;
+}
+
+static int gpio_siox_direction_input(struct gpio_chip *chip,
+				     unsigned int offset)
+{
+	if (offset >= 12)
+		return -EINVAL;
+
+	return 0;
+}
+
+static int gpio_siox_direction_output(struct gpio_chip *chip,
+				      unsigned int offset, int value)
+{
+	if (offset < 12)
+		return -EINVAL;
+
+	return gpio_siox_set(chip, offset, value);
+}
+
+static int gpio_siox_get_direction(struct gpio_chip *chip, unsigned int offset)
+{
+	if (offset < 12)
+		return GPIO_LINE_DIRECTION_IN;
+	else
+		return GPIO_LINE_DIRECTION_OUT;
+}
+
+static const struct irq_chip gpio_siox_irq_chip = {
+	.name = "siox-gpio",
+	.irq_ack = gpio_siox_irq_ack,
+	.irq_mask = gpio_siox_irq_mask,
+	.irq_unmask = gpio_siox_irq_unmask,
+	.irq_set_type = gpio_siox_irq_set_type,
+	.flags = IRQCHIP_IMMUTABLE,
+	GPIOCHIP_IRQ_RESOURCE_HELPERS,
+};
+
+static int gpio_siox_probe(struct siox_device *sdevice)
+{
+	struct gpio_siox_ddata *ddata;
+	struct gpio_irq_chip *girq;
+	struct device *dev = &sdevice->dev;
+	struct gpio_chip *gc;
+	int ret;
+
+	ddata = devm_kzalloc(dev, sizeof(*ddata), GFP_KERNEL);
+	if (!ddata)
+		return -ENOMEM;
+
+	dev_set_drvdata(dev, ddata);
+
+	mutex_init(&ddata->lock);
+	raw_spin_lock_init(&ddata->irqlock);
+
+	gc = &ddata->gchip;
+	gc->base = -1;
+	gc->can_sleep = 1;
+	gc->parent = dev;
+	gc->owner = THIS_MODULE;
+	gc->get = gpio_siox_get;
+	gc->set = gpio_siox_set;
+	gc->direction_input = gpio_siox_direction_input;
+	gc->direction_output = gpio_siox_direction_output;
+	gc->get_direction = gpio_siox_get_direction;
+	gc->ngpio = 20;
+
+	girq = &gc->irq;
+	gpio_irq_chip_set_chip(girq, &gpio_siox_irq_chip);
+	girq->default_type = IRQ_TYPE_NONE;
+	girq->handler = handle_level_irq;
+	girq->threaded = true;
+
+	ret = devm_gpiochip_add_data(dev, gc, ddata);
+	if (ret)
+		dev_err(dev, "Failed to register gpio chip (%d)\n", ret);
+
+	return ret;
+}
+
+static struct siox_driver gpio_siox_driver = {
+	.probe = gpio_siox_probe,
+	.set_data = gpio_siox_set_data,
+	.get_data = gpio_siox_get_data,
+	.driver = {
+		.name = "gpio-siox",
+	},
+};
+module_siox_driver(gpio_siox_driver);
+
+MODULE_AUTHOR("Uwe Kleine-Koenig <u.kleine-koenig@pengutronix.de>");
+MODULE_DESCRIPTION("SIOX gpio driver");
+MODULE_LICENSE("GPL v2");