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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_KHO_RADIX_TREE_H
#define _LINUX_KHO_RADIX_TREE_H
#include <linux/err.h>
#include <linux/errno.h>
#include <linux/mutex_types.h>
#include <linux/types.h>
/**
* DOC: Kexec Handover Radix Tree
*
* This is a radix tree implementation for tracking physical memory pages
* across kexec transitions. It was developed for the KHO mechanism but is
* designed for broader use by any subsystem that needs to preserve pages.
*
* The radix tree is a multi-level tree where leaf nodes are bitmaps
* representing individual pages. To allow pages of different sizes (orders)
* to be stored efficiently in a single tree, it uses a unique key encoding
* scheme. Each key is an unsigned long that combines a page's physical
* address and its order.
*
* Client code is responsible for allocating the root node of the tree,
* initializing the mutex lock, and managing its lifecycle. It must use the
* tree data structures defined in the KHO ABI,
* `include/linux/kho/abi/kexec_handover.h`.
*/
struct kho_radix_node;
struct kho_radix_tree {
struct kho_radix_node *root;
struct mutex lock; /* protects the tree's structure and root pointer */
};
typedef int (*kho_radix_tree_walk_callback_t)(phys_addr_t phys,
unsigned int order);
#ifdef CONFIG_KEXEC_HANDOVER
int kho_radix_add_page(struct kho_radix_tree *tree, unsigned long pfn,
unsigned int order);
void kho_radix_del_page(struct kho_radix_tree *tree, unsigned long pfn,
unsigned int order);
int kho_radix_walk_tree(struct kho_radix_tree *tree,
kho_radix_tree_walk_callback_t cb);
#else /* #ifdef CONFIG_KEXEC_HANDOVER */
static inline int kho_radix_add_page(struct kho_radix_tree *tree, long pfn,
unsigned int order)
{
return -EOPNOTSUPP;
}
static inline void kho_radix_del_page(struct kho_radix_tree *tree,
unsigned long pfn, unsigned int order) { }
static inline int kho_radix_walk_tree(struct kho_radix_tree *tree,
kho_radix_tree_walk_callback_t cb)
{
return -EOPNOTSUPP;
}
#endif /* #ifdef CONFIG_KEXEC_HANDOVER */
#endif /* _LINUX_KHO_RADIX_TREE_H */
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