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, 494 insertions, 0 deletions

diff --git a/drivers/acpi/acpica/nsalloc.c b/drivers/acpi/acpica/nsalloc.c
new file mode 100644
index 000000000..83d26abcf
--- /dev/null
+++ b/drivers/acpi/acpica/nsalloc.c
@@ -0,0 +1,494 @@
+// SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0
+/*******************************************************************************
+ *
+ * Module Name: nsalloc - Namespace allocation and deletion utilities
+ *
+ ******************************************************************************/
+
+#include <acpi/acpi.h>
+#include "accommon.h"
+#include "acnamesp.h"
+
+#define _COMPONENT          ACPI_NAMESPACE
+ACPI_MODULE_NAME("nsalloc")
+
+/*******************************************************************************
+ *
+ * FUNCTION:    acpi_ns_create_node
+ *
+ * PARAMETERS:  name            - Name of the new node (4 char ACPI name)
+ *
+ * RETURN:      New namespace node (Null on failure)
+ *
+ * DESCRIPTION: Create a namespace node
+ *
+ ******************************************************************************/
+struct acpi_namespace_node *acpi_ns_create_node(u32 name)
+{
+	struct acpi_namespace_node *node;
+#ifdef ACPI_DBG_TRACK_ALLOCATIONS
+	u32 temp;
+#endif
+
+	ACPI_FUNCTION_TRACE(ns_create_node);
+
+	node = acpi_os_acquire_object(acpi_gbl_namespace_cache);
+	if (!node) {
+		return_PTR(NULL);
+	}
+
+	ACPI_MEM_TRACKING(acpi_gbl_ns_node_list->total_allocated++);
+
+#ifdef ACPI_DBG_TRACK_ALLOCATIONS
+	temp = acpi_gbl_ns_node_list->total_allocated -
+	    acpi_gbl_ns_node_list->total_freed;
+	if (temp > acpi_gbl_ns_node_list->max_occupied) {
+		acpi_gbl_ns_node_list->max_occupied = temp;
+	}
+#endif
+
+	node->name.integer = name;
+	ACPI_SET_DESCRIPTOR_TYPE(node, ACPI_DESC_TYPE_NAMED);
+	return_PTR(node);
+}
+
+/*******************************************************************************
+ *
+ * FUNCTION:    acpi_ns_delete_node
+ *
+ * PARAMETERS:  node            - Node to be deleted
+ *
+ * RETURN:      None
+ *
+ * DESCRIPTION: Delete a namespace node. All node deletions must come through
+ *              here. Detaches any attached objects, including any attached
+ *              data. If a handler is associated with attached data, it is
+ *              invoked before the node is deleted.
+ *
+ ******************************************************************************/
+
+void acpi_ns_delete_node(struct acpi_namespace_node *node)
+{
+	union acpi_operand_object *obj_desc;
+	union acpi_operand_object *next_desc;
+
+	ACPI_FUNCTION_NAME(ns_delete_node);
+
+	if (!node) {
+		return_VOID;
+	}
+
+	/* Detach an object if there is one */
+
+	acpi_ns_detach_object(node);
+
+	/*
+	 * Delete an attached data object list if present (objects that were
+	 * attached via acpi_attach_data). Note: After any normal object is
+	 * detached above, the only possible remaining object(s) are data
+	 * objects, in a linked list.
+	 */
+	obj_desc = node->object;
+	while (obj_desc && (obj_desc->common.type == ACPI_TYPE_LOCAL_DATA)) {
+
+		/* Invoke the attached data deletion handler if present */
+
+		if (obj_desc->data.handler) {
+			obj_desc->data.handler(node, obj_desc->data.pointer);
+		}
+
+		next_desc = obj_desc->common.next_object;
+		acpi_ut_remove_reference(obj_desc);
+		obj_desc = next_desc;
+	}
+
+	/* Special case for the statically allocated root node */
+
+	if (node == acpi_gbl_root_node) {
+		return;
+	}
+
+	/* Now we can delete the node */
+
+	(void)acpi_os_release_object(acpi_gbl_namespace_cache, node);
+
+	ACPI_MEM_TRACKING(acpi_gbl_ns_node_list->total_freed++);
+	ACPI_DEBUG_PRINT((ACPI_DB_ALLOCATIONS, "Node %p, Remaining %X\n",
+			  node, acpi_gbl_current_node_count));
+}
+
+/*******************************************************************************
+ *
+ * FUNCTION:    acpi_ns_remove_node
+ *
+ * PARAMETERS:  node            - Node to be removed/deleted
+ *
+ * RETURN:      None
+ *
+ * DESCRIPTION: Remove (unlink) and delete a namespace node
+ *
+ ******************************************************************************/
+
+void acpi_ns_remove_node(struct acpi_namespace_node *node)
+{
+	struct acpi_namespace_node *parent_node;
+	struct acpi_namespace_node *prev_node;
+	struct acpi_namespace_node *next_node;
+
+	ACPI_FUNCTION_TRACE_PTR(ns_remove_node, node);
+
+	parent_node = node->parent;
+
+	prev_node = NULL;
+	next_node = parent_node->child;
+
+	/* Find the node that is the previous peer in the parent's child list */
+
+	while (next_node != node) {
+		prev_node = next_node;
+		next_node = next_node->peer;
+	}
+
+	if (prev_node) {
+
+		/* Node is not first child, unlink it */
+
+		prev_node->peer = node->peer;
+	} else {
+		/*
+		 * Node is first child (has no previous peer).
+		 * Link peer list to parent
+		 */
+		parent_node->child = node->peer;
+	}
+
+	/* Delete the node and any attached objects */
+
+	acpi_ns_delete_node(node);
+	return_VOID;
+}
+
+/*******************************************************************************
+ *
+ * FUNCTION:    acpi_ns_install_node
+ *
+ * PARAMETERS:  walk_state      - Current state of the walk
+ *              parent_node     - The parent of the new Node
+ *              node            - The new Node to install
+ *              type            - ACPI object type of the new Node
+ *
+ * RETURN:      None
+ *
+ * DESCRIPTION: Initialize a new namespace node and install it amongst
+ *              its peers.
+ *
+ *              Note: Current namespace lookup is linear search. This appears
+ *              to be sufficient as namespace searches consume only a small
+ *              fraction of the execution time of the ACPI subsystem.
+ *
+ ******************************************************************************/
+
+void acpi_ns_install_node(struct acpi_walk_state *walk_state, struct acpi_namespace_node *parent_node,	/* Parent */
+			  struct acpi_namespace_node *node,	/* New Child */
+			  acpi_object_type type)
+{
+	acpi_owner_id owner_id = 0;
+	struct acpi_namespace_node *child_node;
+
+	ACPI_FUNCTION_TRACE(ns_install_node);
+
+	if (walk_state) {
+		/*
+		 * Get the owner ID from the Walk state. The owner ID is used to
+		 * track table deletion and deletion of objects created by methods.
+		 */
+		owner_id = walk_state->owner_id;
+
+		if ((walk_state->method_desc) &&
+		    (parent_node != walk_state->method_node)) {
+			/*
+			 * A method is creating a new node that is not a child of the
+			 * method (it is non-local). Mark the executing method as having
+			 * modified the namespace. This is used for cleanup when the
+			 * method exits.
+			 */
+			walk_state->method_desc->method.info_flags |=
+			    ACPI_METHOD_MODIFIED_NAMESPACE;
+		}
+	}
+
+	/* Link the new entry into the parent and existing children */
+
+	node->peer = NULL;
+	node->parent = parent_node;
+	child_node = parent_node->child;
+
+	if (!child_node) {
+		parent_node->child = node;
+	} else {
+		/* Add node to the end of the peer list */
+
+		while (child_node->peer) {
+			child_node = child_node->peer;
+		}
+
+		child_node->peer = node;
+	}
+
+	/* Init the new entry */
+
+	node->owner_id = owner_id;
+	node->type = (u8) type;
+
+	ACPI_DEBUG_PRINT((ACPI_DB_NAMES,
+			  "%4.4s (%s) [Node %p Owner %3.3X] added to %4.4s (%s) [Node %p]\n",
+			  acpi_ut_get_node_name(node),
+			  acpi_ut_get_type_name(node->type), node, owner_id,
+			  acpi_ut_get_node_name(parent_node),
+			  acpi_ut_get_type_name(parent_node->type),
+			  parent_node));
+
+	return_VOID;
+}
+
+/*******************************************************************************
+ *
+ * FUNCTION:    acpi_ns_delete_children
+ *
+ * PARAMETERS:  parent_node     - Delete this objects children
+ *
+ * RETURN:      None.
+ *
+ * DESCRIPTION: Delete all children of the parent object. In other words,
+ *              deletes a "scope".
+ *
+ ******************************************************************************/
+
+void acpi_ns_delete_children(struct acpi_namespace_node *parent_node)
+{
+	struct acpi_namespace_node *next_node;
+	struct acpi_namespace_node *node_to_delete;
+
+	ACPI_FUNCTION_TRACE_PTR(ns_delete_children, parent_node);
+
+	if (!parent_node) {
+		return_VOID;
+	}
+
+	/* Deallocate all children at this level */
+
+	next_node = parent_node->child;
+	while (next_node) {
+
+		/* Grandchildren should have all been deleted already */
+
+		if (next_node->child) {
+			ACPI_ERROR((AE_INFO, "Found a grandchild! P=%p C=%p",
+				    parent_node, next_node));
+		}
+
+		/*
+		 * Delete this child node and move on to the next child in the list.
+		 * No need to unlink the node since we are deleting the entire branch.
+		 */
+		node_to_delete = next_node;
+		next_node = next_node->peer;
+		acpi_ns_delete_node(node_to_delete);
+	}
+
+	/* Clear the parent's child pointer */
+
+	parent_node->child = NULL;
+	return_VOID;
+}
+
+/*******************************************************************************
+ *
+ * FUNCTION:    acpi_ns_delete_namespace_subtree
+ *
+ * PARAMETERS:  parent_node     - Root of the subtree to be deleted
+ *
+ * RETURN:      None.
+ *
+ * DESCRIPTION: Delete a subtree of the namespace. This includes all objects
+ *              stored within the subtree.
+ *
+ ******************************************************************************/
+
+void acpi_ns_delete_namespace_subtree(struct acpi_namespace_node *parent_node)
+{
+	struct acpi_namespace_node *child_node = NULL;
+	u32 level = 1;
+	acpi_status status;
+
+	ACPI_FUNCTION_TRACE(ns_delete_namespace_subtree);
+
+	if (!parent_node) {
+		return_VOID;
+	}
+
+	/* Lock namespace for possible update */
+
+	status = acpi_ut_acquire_mutex(ACPI_MTX_NAMESPACE);
+	if (ACPI_FAILURE(status)) {
+		return_VOID;
+	}
+
+	/*
+	 * Traverse the tree of objects until we bubble back up
+	 * to where we started.
+	 */
+	while (level > 0) {
+
+		/* Get the next node in this scope (NULL if none) */
+
+		child_node = acpi_ns_get_next_node(parent_node, child_node);
+		if (child_node) {
+
+			/* Found a child node - detach any attached object */
+
+			acpi_ns_detach_object(child_node);
+
+			/* Check if this node has any children */
+
+			if (child_node->child) {
+				/*
+				 * There is at least one child of this node,
+				 * visit the node
+				 */
+				level++;
+				parent_node = child_node;
+				child_node = NULL;
+			}
+		} else {
+			/*
+			 * No more children of this parent node.
+			 * Move up to the grandparent.
+			 */
+			level--;
+
+			/*
+			 * Now delete all of the children of this parent
+			 * all at the same time.
+			 */
+			acpi_ns_delete_children(parent_node);
+
+			/* New "last child" is this parent node */
+
+			child_node = parent_node;
+
+			/* Move up the tree to the grandparent */
+
+			parent_node = parent_node->parent;
+		}
+	}
+
+	(void)acpi_ut_release_mutex(ACPI_MTX_NAMESPACE);
+	return_VOID;
+}
+
+/*******************************************************************************
+ *
+ * FUNCTION:    acpi_ns_delete_namespace_by_owner
+ *
+ * PARAMETERS:  owner_id    - All nodes with this owner will be deleted
+ *
+ * RETURN:      Status
+ *
+ * DESCRIPTION: Delete entries within the namespace that are owned by a
+ *              specific ID. Used to delete entire ACPI tables. All
+ *              reference counts are updated.
+ *
+ * MUTEX:       Locks namespace during deletion walk.
+ *
+ ******************************************************************************/
+
+void acpi_ns_delete_namespace_by_owner(acpi_owner_id owner_id)
+{
+	struct acpi_namespace_node *child_node;
+	struct acpi_namespace_node *deletion_node;
+	struct acpi_namespace_node *parent_node;
+	u32 level;
+	acpi_status status;
+
+	ACPI_FUNCTION_TRACE_U32(ns_delete_namespace_by_owner, owner_id);
+
+	if (owner_id == 0) {
+		return_VOID;
+	}
+
+	/* Lock namespace for possible update */
+
+	status = acpi_ut_acquire_mutex(ACPI_MTX_NAMESPACE);
+	if (ACPI_FAILURE(status)) {
+		return_VOID;
+	}
+
+	deletion_node = NULL;
+	parent_node = acpi_gbl_root_node;
+	child_node = NULL;
+	level = 1;
+
+	/*
+	 * Traverse the tree of nodes until we bubble back up
+	 * to where we started.
+	 */
+	while (level > 0) {
+		/*
+		 * Get the next child of this parent node. When child_node is NULL,
+		 * the first child of the parent is returned
+		 */
+		child_node = acpi_ns_get_next_node(parent_node, child_node);
+
+		if (deletion_node) {
+			acpi_ns_delete_children(deletion_node);
+			acpi_ns_remove_node(deletion_node);
+			deletion_node = NULL;
+		}
+
+		if (child_node) {
+			if (child_node->owner_id == owner_id) {
+
+				/* Found a matching child node - detach any attached object */
+
+				acpi_ns_detach_object(child_node);
+			}
+
+			/* Check if this node has any children */
+
+			if (child_node->child) {
+				/*
+				 * There is at least one child of this node,
+				 * visit the node
+				 */
+				level++;
+				parent_node = child_node;
+				child_node = NULL;
+			} else if (child_node->owner_id == owner_id) {
+				deletion_node = child_node;
+			}
+		} else {
+			/*
+			 * No more children of this parent node.
+			 * Move up to the grandparent.
+			 */
+			level--;
+			if (level != 0) {
+				if (parent_node->owner_id == owner_id) {
+					deletion_node = parent_node;
+				}
+			}
+
+			/* New "last child" is this parent node */
+
+			child_node = parent_node;
+
+			/* Move up the tree to the grandparent */
+
+			parent_node = parent_node->parent;
+		}
+	}
+
+	(void)acpi_ut_release_mutex(ACPI_MTX_NAMESPACE);
+	return_VOID;
+}