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, 399 insertions, 0 deletions

diff --git a/lib/devres.c b/lib/devres.c
new file mode 100644
index 000000000..378b07730
--- /dev/null
+++ b/lib/devres.c
@@ -0,0 +1,399 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/bug.h>
+#include <linux/device.h>
+#include <linux/errno.h>
+#include <linux/export.h>
+#include <linux/gfp_types.h>
+#include <linux/io.h>
+#include <linux/ioport.h>
+#include <linux/of_address.h>
+#include <linux/types.h>
+
+enum devm_ioremap_type {
+	DEVM_IOREMAP = 0,
+	DEVM_IOREMAP_UC,
+	DEVM_IOREMAP_WC,
+	DEVM_IOREMAP_NP,
+};
+
+void devm_ioremap_release(struct device *dev, void *res)
+{
+	iounmap(*(void __iomem **)res);
+}
+
+static int devm_ioremap_match(struct device *dev, void *res, void *match_data)
+{
+	return *(void **)res == match_data;
+}
+
+static void __iomem *__devm_ioremap(struct device *dev, resource_size_t offset,
+				    resource_size_t size,
+				    enum devm_ioremap_type type)
+{
+	void __iomem **ptr, *addr = NULL;
+
+	ptr = devres_alloc_node(devm_ioremap_release, sizeof(*ptr), GFP_KERNEL,
+				dev_to_node(dev));
+	if (!ptr)
+		return NULL;
+
+	switch (type) {
+	case DEVM_IOREMAP:
+		addr = ioremap(offset, size);
+		break;
+	case DEVM_IOREMAP_UC:
+		addr = ioremap_uc(offset, size);
+		break;
+	case DEVM_IOREMAP_WC:
+		addr = ioremap_wc(offset, size);
+		break;
+	case DEVM_IOREMAP_NP:
+		addr = ioremap_np(offset, size);
+		break;
+	}
+
+	if (addr) {
+		*ptr = addr;
+		devres_add(dev, ptr);
+	} else
+		devres_free(ptr);
+
+	return addr;
+}
+
+/**
+ * devm_ioremap - Managed ioremap()
+ * @dev: Generic device to remap IO address for
+ * @offset: Resource address to map
+ * @size: Size of map
+ *
+ * Managed ioremap().  Map is automatically unmapped on driver detach.
+ */
+void __iomem *devm_ioremap(struct device *dev, resource_size_t offset,
+			   resource_size_t size)
+{
+	return __devm_ioremap(dev, offset, size, DEVM_IOREMAP);
+}
+EXPORT_SYMBOL(devm_ioremap);
+
+/**
+ * devm_ioremap_uc - Managed ioremap_uc()
+ * @dev: Generic device to remap IO address for
+ * @offset: Resource address to map
+ * @size: Size of map
+ *
+ * Managed ioremap_uc().  Map is automatically unmapped on driver detach.
+ */
+void __iomem *devm_ioremap_uc(struct device *dev, resource_size_t offset,
+			      resource_size_t size)
+{
+	return __devm_ioremap(dev, offset, size, DEVM_IOREMAP_UC);
+}
+EXPORT_SYMBOL_GPL(devm_ioremap_uc);
+
+/**
+ * devm_ioremap_wc - Managed ioremap_wc()
+ * @dev: Generic device to remap IO address for
+ * @offset: Resource address to map
+ * @size: Size of map
+ *
+ * Managed ioremap_wc().  Map is automatically unmapped on driver detach.
+ */
+void __iomem *devm_ioremap_wc(struct device *dev, resource_size_t offset,
+			      resource_size_t size)
+{
+	return __devm_ioremap(dev, offset, size, DEVM_IOREMAP_WC);
+}
+EXPORT_SYMBOL(devm_ioremap_wc);
+
+/**
+ * devm_iounmap - Managed iounmap()
+ * @dev: Generic device to unmap for
+ * @addr: Address to unmap
+ *
+ * Managed iounmap().  @addr must have been mapped using devm_ioremap*().
+ */
+void devm_iounmap(struct device *dev, void __iomem *addr)
+{
+	WARN_ON(devres_release(dev, devm_ioremap_release, devm_ioremap_match,
+			       (__force void *)addr));
+}
+EXPORT_SYMBOL(devm_iounmap);
+
+static void __iomem *
+__devm_ioremap_resource(struct device *dev, const struct resource *res,
+			enum devm_ioremap_type type)
+{
+	resource_size_t size;
+	void __iomem *dest_ptr;
+	char *pretty_name;
+	int ret;
+
+	BUG_ON(!dev);
+
+	if (!res || resource_type(res) != IORESOURCE_MEM) {
+		ret = dev_err_probe(dev, -EINVAL, "invalid resource %pR\n", res);
+		return IOMEM_ERR_PTR(ret);
+	}
+
+	if (type == DEVM_IOREMAP && res->flags & IORESOURCE_MEM_NONPOSTED)
+		type = DEVM_IOREMAP_NP;
+
+	size = resource_size(res);
+
+	if (res->name)
+		pretty_name = devm_kasprintf(dev, GFP_KERNEL, "%s %s",
+					     dev_name(dev), res->name);
+	else
+		pretty_name = devm_kstrdup(dev, dev_name(dev), GFP_KERNEL);
+	if (!pretty_name) {
+		ret = dev_err_probe(dev, -ENOMEM, "can't generate pretty name for resource %pR\n", res);
+		return IOMEM_ERR_PTR(ret);
+	}
+
+	if (!devm_request_mem_region(dev, res->start, size, pretty_name)) {
+		ret = dev_err_probe(dev, -EBUSY, "can't request region for resource %pR\n", res);
+		return IOMEM_ERR_PTR(ret);
+	}
+
+	dest_ptr = __devm_ioremap(dev, res->start, size, type);
+	if (!dest_ptr) {
+		devm_release_mem_region(dev, res->start, size);
+		ret = dev_err_probe(dev, -ENOMEM, "ioremap failed for resource %pR\n", res);
+		return IOMEM_ERR_PTR(ret);
+	}
+
+	return dest_ptr;
+}
+
+/**
+ * devm_ioremap_resource() - check, request region, and ioremap resource
+ * @dev: generic device to handle the resource for
+ * @res: resource to be handled
+ *
+ * Checks that a resource is a valid memory region, requests the memory
+ * region and ioremaps it. All operations are managed and will be undone
+ * on driver detach.
+ *
+ * Usage example:
+ *
+ *	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ *	base = devm_ioremap_resource(&pdev->dev, res);
+ *	if (IS_ERR(base))
+ *		return PTR_ERR(base);
+ *
+ * Return: a pointer to the remapped memory or an ERR_PTR() encoded error code
+ * on failure.
+ */
+void __iomem *devm_ioremap_resource(struct device *dev,
+				    const struct resource *res)
+{
+	return __devm_ioremap_resource(dev, res, DEVM_IOREMAP);
+}
+EXPORT_SYMBOL(devm_ioremap_resource);
+
+/**
+ * devm_ioremap_resource_wc() - write-combined variant of
+ *				devm_ioremap_resource()
+ * @dev: generic device to handle the resource for
+ * @res: resource to be handled
+ *
+ * Return: a pointer to the remapped memory or an ERR_PTR() encoded error code
+ * on failure.
+ */
+void __iomem *devm_ioremap_resource_wc(struct device *dev,
+				       const struct resource *res)
+{
+	return __devm_ioremap_resource(dev, res, DEVM_IOREMAP_WC);
+}
+EXPORT_SYMBOL(devm_ioremap_resource_wc);
+
+/*
+ * devm_of_iomap - Requests a resource and maps the memory mapped IO
+ *		   for a given device_node managed by a given device
+ *
+ * Checks that a resource is a valid memory region, requests the memory
+ * region and ioremaps it. All operations are managed and will be undone
+ * on driver detach of the device.
+ *
+ * This is to be used when a device requests/maps resources described
+ * by other device tree nodes (children or otherwise).
+ *
+ * @dev:	The device "managing" the resource
+ * @node:       The device-tree node where the resource resides
+ * @index:	index of the MMIO range in the "reg" property
+ * @size:	Returns the size of the resource (pass NULL if not needed)
+ *
+ * Usage example:
+ *
+ *	base = devm_of_iomap(&pdev->dev, node, 0, NULL);
+ *	if (IS_ERR(base))
+ *		return PTR_ERR(base);
+ *
+ * Please Note: This is not a one-to-one replacement for of_iomap() because the
+ * of_iomap() function does not track whether the region is already mapped.  If
+ * two drivers try to map the same memory, the of_iomap() function will succeed
+ * but the devm_of_iomap() function will return -EBUSY.
+ *
+ * Return: a pointer to the requested and mapped memory or an ERR_PTR() encoded
+ * error code on failure.
+ */
+void __iomem *devm_of_iomap(struct device *dev, struct device_node *node, int index,
+			    resource_size_t *size)
+{
+	struct resource res;
+
+	if (of_address_to_resource(node, index, &res))
+		return IOMEM_ERR_PTR(-EINVAL);
+	if (size)
+		*size = resource_size(&res);
+	return devm_ioremap_resource(dev, &res);
+}
+EXPORT_SYMBOL(devm_of_iomap);
+
+#ifdef CONFIG_HAS_IOPORT_MAP
+/*
+ * Generic iomap devres
+ */
+static void devm_ioport_map_release(struct device *dev, void *res)
+{
+	ioport_unmap(*(void __iomem **)res);
+}
+
+static int devm_ioport_map_match(struct device *dev, void *res,
+				 void *match_data)
+{
+	return *(void **)res == match_data;
+}
+
+/**
+ * devm_ioport_map - Managed ioport_map()
+ * @dev: Generic device to map ioport for
+ * @port: Port to map
+ * @nr: Number of ports to map
+ *
+ * Managed ioport_map().  Map is automatically unmapped on driver
+ * detach.
+ *
+ * Return: a pointer to the remapped memory or NULL on failure.
+ */
+void __iomem *devm_ioport_map(struct device *dev, unsigned long port,
+			       unsigned int nr)
+{
+	void __iomem **ptr, *addr;
+
+	ptr = devres_alloc_node(devm_ioport_map_release, sizeof(*ptr), GFP_KERNEL,
+				dev_to_node(dev));
+	if (!ptr)
+		return NULL;
+
+	addr = ioport_map(port, nr);
+	if (addr) {
+		*ptr = addr;
+		devres_add(dev, ptr);
+	} else
+		devres_free(ptr);
+
+	return addr;
+}
+EXPORT_SYMBOL(devm_ioport_map);
+
+/**
+ * devm_ioport_unmap - Managed ioport_unmap()
+ * @dev: Generic device to unmap for
+ * @addr: Address to unmap
+ *
+ * Managed ioport_unmap().  @addr must have been mapped using
+ * devm_ioport_map().
+ */
+void devm_ioport_unmap(struct device *dev, void __iomem *addr)
+{
+	WARN_ON(devres_release(dev, devm_ioport_map_release,
+			       devm_ioport_map_match, (__force void *)addr));
+}
+EXPORT_SYMBOL(devm_ioport_unmap);
+#endif /* CONFIG_HAS_IOPORT_MAP */
+
+static void devm_arch_phys_ac_add_release(struct device *dev, void *res)
+{
+	arch_phys_wc_del(*((int *)res));
+}
+
+/**
+ * devm_arch_phys_wc_add - Managed arch_phys_wc_add()
+ * @dev: Managed device
+ * @base: Memory base address
+ * @size: Size of memory range
+ *
+ * Adds a WC MTRR using arch_phys_wc_add() and sets up a release callback.
+ * See arch_phys_wc_add() for more information.
+ */
+int devm_arch_phys_wc_add(struct device *dev, unsigned long base, unsigned long size)
+{
+	int *mtrr;
+	int ret;
+
+	mtrr = devres_alloc_node(devm_arch_phys_ac_add_release, sizeof(*mtrr), GFP_KERNEL,
+				 dev_to_node(dev));
+	if (!mtrr)
+		return -ENOMEM;
+
+	ret = arch_phys_wc_add(base, size);
+	if (ret < 0) {
+		devres_free(mtrr);
+		return ret;
+	}
+
+	*mtrr = ret;
+	devres_add(dev, mtrr);
+
+	return ret;
+}
+EXPORT_SYMBOL(devm_arch_phys_wc_add);
+
+struct arch_io_reserve_memtype_wc_devres {
+	resource_size_t start;
+	resource_size_t size;
+};
+
+static void devm_arch_io_free_memtype_wc_release(struct device *dev, void *res)
+{
+	const struct arch_io_reserve_memtype_wc_devres *this = res;
+
+	arch_io_free_memtype_wc(this->start, this->size);
+}
+
+/**
+ * devm_arch_io_reserve_memtype_wc - Managed arch_io_reserve_memtype_wc()
+ * @dev: Managed device
+ * @start: Memory base address
+ * @size: Size of memory range
+ *
+ * Reserves a memory range with WC caching using arch_io_reserve_memtype_wc()
+ * and sets up a release callback See arch_io_reserve_memtype_wc() for more
+ * information.
+ */
+int devm_arch_io_reserve_memtype_wc(struct device *dev, resource_size_t start,
+				    resource_size_t size)
+{
+	struct arch_io_reserve_memtype_wc_devres *dr;
+	int ret;
+
+	dr = devres_alloc_node(devm_arch_io_free_memtype_wc_release, sizeof(*dr), GFP_KERNEL,
+			       dev_to_node(dev));
+	if (!dr)
+		return -ENOMEM;
+
+	ret = arch_io_reserve_memtype_wc(start, size);
+	if (ret < 0) {
+		devres_free(dr);
+		return ret;
+	}
+
+	dr->start = start;
+	dr->size = size;
+	devres_add(dev, dr);
+
+	return ret;
+}
+EXPORT_SYMBOL(devm_arch_io_reserve_memtype_wc);