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, 195 insertions, 0 deletions

diff --git a/drivers/gpio/gpio-reg.c b/drivers/gpio/gpio-reg.c
new file mode 100644
index 000000000..296c210b2
--- /dev/null
+++ b/drivers/gpio/gpio-reg.c
@@ -0,0 +1,195 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * gpio-reg: single register individually fixed-direction GPIOs
+ *
+ * Copyright (C) 2016 Russell King
+ */
+#include <linux/bits.h>
+#include <linux/container_of.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/errno.h>
+#include <linux/io.h>
+#include <linux/irqdomain.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/types.h>
+
+#include <linux/gpio/driver.h>
+#include <linux/gpio/gpio-reg.h>
+
+struct gpio_reg {
+	struct gpio_chip gc;
+	spinlock_t lock;
+	u32 direction;
+	u32 out;
+	void __iomem *reg;
+	struct irq_domain *irqdomain;
+	const int *irqs;
+};
+
+#define to_gpio_reg(x) container_of(x, struct gpio_reg, gc)
+
+static int gpio_reg_get_direction(struct gpio_chip *gc, unsigned offset)
+{
+	struct gpio_reg *r = to_gpio_reg(gc);
+
+	return r->direction & BIT(offset) ? GPIO_LINE_DIRECTION_IN :
+					    GPIO_LINE_DIRECTION_OUT;
+}
+
+static int gpio_reg_direction_output(struct gpio_chip *gc, unsigned offset,
+	int value)
+{
+	struct gpio_reg *r = to_gpio_reg(gc);
+
+	if (r->direction & BIT(offset))
+		return -ENOTSUPP;
+
+	gc->set(gc, offset, value);
+	return 0;
+}
+
+static int gpio_reg_direction_input(struct gpio_chip *gc, unsigned offset)
+{
+	struct gpio_reg *r = to_gpio_reg(gc);
+
+	return r->direction & BIT(offset) ? 0 : -ENOTSUPP;
+}
+
+static int gpio_reg_set(struct gpio_chip *gc, unsigned int offset, int value)
+{
+	struct gpio_reg *r = to_gpio_reg(gc);
+	unsigned long flags;
+	u32 val, mask = BIT(offset);
+
+	spin_lock_irqsave(&r->lock, flags);
+	val = r->out;
+	if (value)
+		val |= mask;
+	else
+		val &= ~mask;
+	r->out = val;
+	writel_relaxed(val, r->reg);
+	spin_unlock_irqrestore(&r->lock, flags);
+
+	return 0;
+}
+
+static int gpio_reg_get(struct gpio_chip *gc, unsigned offset)
+{
+	struct gpio_reg *r = to_gpio_reg(gc);
+	u32 val, mask = BIT(offset);
+
+	if (r->direction & mask) {
+		/*
+		 * double-read the value, some registers latch after the
+		 * first read.
+		 */
+		readl_relaxed(r->reg);
+		val = readl_relaxed(r->reg);
+	} else {
+		val = r->out;
+	}
+	return !!(val & mask);
+}
+
+static int gpio_reg_set_multiple(struct gpio_chip *gc, unsigned long *mask,
+				 unsigned long *bits)
+{
+	struct gpio_reg *r = to_gpio_reg(gc);
+	unsigned long flags;
+
+	spin_lock_irqsave(&r->lock, flags);
+	r->out = (r->out & ~*mask) | (*bits & *mask);
+	writel_relaxed(r->out, r->reg);
+	spin_unlock_irqrestore(&r->lock, flags);
+
+	return 0;
+}
+
+static int gpio_reg_to_irq(struct gpio_chip *gc, unsigned offset)
+{
+	struct gpio_reg *r = to_gpio_reg(gc);
+	int irq = r->irqs[offset];
+
+	if (irq >= 0 && r->irqdomain)
+		irq = irq_find_mapping(r->irqdomain, irq);
+
+	return irq;
+}
+
+/**
+ * gpio_reg_init - add a fixed in/out register as gpio
+ * @dev: optional struct device associated with this register
+ * @base: start gpio number, or -1 to allocate
+ * @num: number of GPIOs, maximum 32
+ * @label: GPIO chip label
+ * @direction: bitmask of fixed direction, one per GPIO signal, 1 = in
+ * @def_out: initial GPIO output value
+ * @names: array of %num strings describing each GPIO signal or %NULL
+ * @irqdom: irq domain or %NULL
+ * @irqs: array of %num ints describing the interrupt mapping for each
+ *        GPIO signal, or %NULL.  If @irqdom is %NULL, then this
+ *        describes the Linux interrupt number, otherwise it describes
+ *        the hardware interrupt number in the specified irq domain.
+ *
+ * Add a single-register GPIO device containing up to 32 GPIO signals,
+ * where each GPIO has a fixed input or output configuration.  Only
+ * input GPIOs are assumed to be readable from the register, and only
+ * then after a double-read.  Output values are assumed not to be
+ * readable.
+ */
+struct gpio_chip *gpio_reg_init(struct device *dev, void __iomem *reg,
+	int base, int num, const char *label, u32 direction, u32 def_out,
+	const char *const *names, struct irq_domain *irqdom, const int *irqs)
+{
+	struct gpio_reg *r;
+	int ret;
+
+	if (dev)
+		r = devm_kzalloc(dev, sizeof(*r), GFP_KERNEL);
+	else
+		r = kzalloc_obj(*r);
+
+	if (!r)
+		return ERR_PTR(-ENOMEM);
+
+	spin_lock_init(&r->lock);
+
+	r->gc.label = label;
+	r->gc.get_direction = gpio_reg_get_direction;
+	r->gc.direction_input = gpio_reg_direction_input;
+	r->gc.direction_output = gpio_reg_direction_output;
+	r->gc.set = gpio_reg_set;
+	r->gc.get = gpio_reg_get;
+	r->gc.set_multiple = gpio_reg_set_multiple;
+	if (irqs)
+		r->gc.to_irq = gpio_reg_to_irq;
+	r->gc.base = base;
+	r->gc.ngpio = num;
+	r->gc.names = names;
+	r->direction = direction;
+	r->out = def_out;
+	r->reg = reg;
+	r->irqs = irqs;
+
+	if (dev)
+		ret = devm_gpiochip_add_data(dev, &r->gc, r);
+	else
+		ret = gpiochip_add_data(&r->gc, r);
+
+	return ret ? ERR_PTR(ret) : &r->gc;
+}
+
+int gpio_reg_resume(struct gpio_chip *gc)
+{
+	struct gpio_reg *r = to_gpio_reg(gc);
+	unsigned long flags;
+
+	spin_lock_irqsave(&r->lock, flags);
+	writel_relaxed(r->out, r->reg);
+	spin_unlock_irqrestore(&r->lock, flags);
+
+	return 0;
+}