xref: /linux/drivers/iommu/generic_pt/pt_iter.h (revision ce5cfb0fa20dc6454da039612e34325b7b4a8243)

/* SPDX-License-Identifier: GPL-2.0-only */
/*
 * Copyright (c) 2024-2025, NVIDIA CORPORATION & AFFILIATES
 *
 * Iterators for Generic Page Table
 */
#ifndef __GENERIC_PT_PT_ITER_H
#define __GENERIC_PT_PT_ITER_H

#include "pt_common.h"

#include <linux/errno.h>

/*
 * Use to mangle symbols so that backtraces and the symbol table are
 * understandable. Any non-inlined function should get mangled like this.
 */
#define NS(fn) CONCATENATE(PTPFX, fn)

/**
 * pt_check_range() - Validate the range can be iterated
 * @range: Range to validate
 *
 * Check that VA and last_va fall within the permitted range of VAs. If the
 * format is using PT_FEAT_SIGN_EXTEND then this also checks the sign extension
 * is correct.
 */
static inline int pt_check_range(struct pt_range *range)
{
	pt_vaddr_t prefix;

	PT_WARN_ON(!range->max_vasz_lg2);

	if (pt_feature(range->common, PT_FEAT_SIGN_EXTEND)) {
		PT_WARN_ON(range->common->max_vasz_lg2 != range->max_vasz_lg2);
		prefix = fvalog2_div(range->va, range->max_vasz_lg2 - 1) ?
				 PT_VADDR_MAX :
				 0;
	} else {
		prefix = pt_full_va_prefix(range->common);
	}

	if (!fvalog2_div_eq(range->va, prefix, range->max_vasz_lg2) ||
	    !fvalog2_div_eq(range->last_va, prefix, range->max_vasz_lg2))
		return -ERANGE;
	return 0;
}

/**
 * pt_index_to_va() - Update range->va to the current pts->index
 * @pts: Iteration State
 *
 * Adjust range->va to match the current index. This is done in a lazy manner
 * since computing the VA takes several instructions and is rarely required.
 */
static inline void pt_index_to_va(struct pt_state *pts)
{
	pt_vaddr_t lower_va;

	lower_va = log2_mul(pts->index, pt_table_item_lg2sz(pts));
	pts->range->va = fvalog2_set_mod(pts->range->va, lower_va,
					 pt_table_oa_lg2sz(pts));
}

/*
 * Add index_count_lg2 number of entries to pts's VA and index. The VA will be
 * adjusted to the end of the contiguous block if it is currently in the middle.
 */
static inline void _pt_advance(struct pt_state *pts,
			       unsigned int index_count_lg2)
{
	pts->index = log2_set_mod(pts->index + log2_to_int(index_count_lg2), 0,
				  index_count_lg2);
}

/**
 * pt_entry_fully_covered() - Check if the item or entry is entirely contained
 *                            within pts->range
 * @pts: Iteration State
 * @oasz_lg2: The size of the item to check, pt_table_item_lg2sz() or
 *            pt_entry_oa_lg2sz()
 *
 * Returns: true if the item is fully enclosed by the pts->range.
 */
static inline bool pt_entry_fully_covered(const struct pt_state *pts,
					  unsigned int oasz_lg2)
{
	struct pt_range *range = pts->range;

	/* Range begins at the start of the entry */
	if (log2_mod(pts->range->va, oasz_lg2))
		return false;

	/* Range ends past the end of the entry */
	if (!log2_div_eq(range->va, range->last_va, oasz_lg2))
		return true;

	/* Range ends at the end of the entry */
	return log2_mod_eq_max(range->last_va, oasz_lg2);
}

/**
 * pt_range_to_index() - Starting index for an iteration
 * @pts: Iteration State
 *
 * Return: the starting index for the iteration in pts.
 */
static inline unsigned int pt_range_to_index(const struct pt_state *pts)
{
	unsigned int isz_lg2 = pt_table_item_lg2sz(pts);

	PT_WARN_ON(pts->level > pts->range->top_level);
	if (pts->range->top_level == pts->level)
		return log2_div(fvalog2_mod(pts->range->va,
					    pts->range->max_vasz_lg2),
				isz_lg2);
	return log2_mod(log2_div(pts->range->va, isz_lg2),
			pt_num_items_lg2(pts));
}

/**
 * pt_range_to_end_index() - Ending index iteration
 * @pts: Iteration State
 *
 * Return: the last index for the iteration in pts.
 */
static inline unsigned int pt_range_to_end_index(const struct pt_state *pts)
{
	unsigned int isz_lg2 = pt_table_item_lg2sz(pts);
	struct pt_range *range = pts->range;
	unsigned int num_entries_lg2;

	if (range->va == range->last_va)
		return pts->index + 1;

	if (pts->range->top_level == pts->level)
		return log2_div(fvalog2_mod(pts->range->last_va,
					    pts->range->max_vasz_lg2),
				isz_lg2) +
		       1;

	num_entries_lg2 = pt_num_items_lg2(pts);

	/* last_va falls within this table */
	if (log2_div_eq(range->va, range->last_va, num_entries_lg2 + isz_lg2))
		return log2_mod(log2_div(pts->range->last_va, isz_lg2),
				num_entries_lg2) +
		       1;

	return log2_to_int(num_entries_lg2);
}

static inline void _pt_iter_first(struct pt_state *pts)
{
	pts->index = pt_range_to_index(pts);
	pts->end_index = pt_range_to_end_index(pts);
	PT_WARN_ON(pts->index > pts->end_index);
}

static inline bool _pt_iter_load(struct pt_state *pts)
{
	if (pts->index >= pts->end_index)
		return false;
	pt_load_entry(pts);
	return true;
}

/**
 * pt_next_entry() - Advance pts to the next entry
 * @pts: Iteration State
 *
 * Update pts to go to the next index at this level. If pts is pointing at a
 * contiguous entry then the index may advance my more than one.
 */
static inline void pt_next_entry(struct pt_state *pts)
{
	if (pts->type == PT_ENTRY_OA &&
	    !__builtin_constant_p(pt_entry_num_contig_lg2(pts) == 0))
		_pt_advance(pts, pt_entry_num_contig_lg2(pts));
	else
		pts->index++;
	pt_index_to_va(pts);
}

/**
 * for_each_pt_level_entry() - For loop wrapper over entries in the range
 * @pts: Iteration State
 *
 * This is the basic iteration primitive. It iterates over all the entries in
 * pts->range that fall within the pts's current table level. Each step does
 * pt_load_entry(pts).
 */
#define for_each_pt_level_entry(pts) \
	for (_pt_iter_first(pts); _pt_iter_load(pts); pt_next_entry(pts))

/**
 * pt_load_single_entry() - Version of pt_load_entry() usable within a walker
 * @pts: Iteration State
 *
 * Alternative to for_each_pt_level_entry() if the walker function uses only a
 * single entry.
 */
static inline enum pt_entry_type pt_load_single_entry(struct pt_state *pts)
{
	pts->index = pt_range_to_index(pts);
	pt_load_entry(pts);
	return pts->type;
}

static __always_inline struct pt_range _pt_top_range(struct pt_common *common,
						     uintptr_t top_of_table)
{
	struct pt_range range = {
		.common = common,
		.top_table =
			(struct pt_table_p *)(top_of_table &
					      ~(uintptr_t)PT_TOP_LEVEL_MASK),
		.top_level = top_of_table % (1 << PT_TOP_LEVEL_BITS),
	};
	struct pt_state pts = { .range = &range, .level = range.top_level };
	unsigned int max_vasz_lg2;

	max_vasz_lg2 = common->max_vasz_lg2;
	if (pt_feature(common, PT_FEAT_DYNAMIC_TOP) &&
	    pts.level != PT_MAX_TOP_LEVEL)
		max_vasz_lg2 = min_t(unsigned int, common->max_vasz_lg2,
				     pt_num_items_lg2(&pts) +
					     pt_table_item_lg2sz(&pts));

	/*
	 * The top range will default to the lower region only with sign extend.
	 */
	range.max_vasz_lg2 = max_vasz_lg2;
	if (pt_feature(common, PT_FEAT_SIGN_EXTEND))
		max_vasz_lg2--;

	range.va = fvalog2_set_mod(pt_full_va_prefix(common), 0, max_vasz_lg2);
	range.last_va =
		fvalog2_set_mod_max(pt_full_va_prefix(common), max_vasz_lg2);
	return range;
}

/**
 * pt_top_range() - Return a range that spans part of the top level
 * @common: Table
 *
 * For PT_FEAT_SIGN_EXTEND this will return the lower range, and cover half the
 * total page table. Otherwise it returns the entire page table.
 */
static __always_inline struct pt_range pt_top_range(struct pt_common *common)
{
	/*
	 * The top pointer can change without locking. We capture the value and
	 * it's level here and are safe to walk it so long as both values are
	 * captured without tearing.
	 */
	return _pt_top_range(common, READ_ONCE(common->top_of_table));
}

/**
 * pt_all_range() - Return a range that spans the entire page table
 * @common: Table
 *
 * The returned range spans the whole page table. Due to how PT_FEAT_SIGN_EXTEND
 * is supported range->va and range->last_va will be incorrect during the
 * iteration and must not be accessed.
 */
static inline struct pt_range pt_all_range(struct pt_common *common)
{
	struct pt_range range = pt_top_range(common);

	if (!pt_feature(common, PT_FEAT_SIGN_EXTEND))
		return range;

	/*
	 * Pretend the table is linear from 0 without a sign extension. This
	 * generates the correct indexes for iteration.
	 */
	range.last_va = fvalog2_set_mod_max(0, range.max_vasz_lg2);
	return range;
}

/**
 * pt_upper_range() - Return a range that spans part of the top level
 * @common: Table
 *
 * For PT_FEAT_SIGN_EXTEND this will return the upper range, and cover half the
 * total page table. Otherwise it returns the entire page table.
 */
static inline struct pt_range pt_upper_range(struct pt_common *common)
{
	struct pt_range range = pt_top_range(common);

	if (!pt_feature(common, PT_FEAT_SIGN_EXTEND))
		return range;

	range.va = fvalog2_set_mod(PT_VADDR_MAX, 0, range.max_vasz_lg2 - 1);
	range.last_va = PT_VADDR_MAX;
	return range;
}

/**
 * pt_make_range() - Return a range that spans part of the table
 * @common: Table
 * @va: Start address
 * @last_va: Last address
 *
 * The caller must validate the range with pt_check_range() before using it.
 */
static __always_inline struct pt_range
pt_make_range(struct pt_common *common, pt_vaddr_t va, pt_vaddr_t last_va)
{
	struct pt_range range =
		_pt_top_range(common, READ_ONCE(common->top_of_table));

	range.va = va;
	range.last_va = last_va;

	return range;
}

/*
 * Span a slice of the table starting at a lower table level from an active
 * walk.
 */
static __always_inline struct pt_range
pt_make_child_range(const struct pt_range *parent, pt_vaddr_t va,
		    pt_vaddr_t last_va)
{
	struct pt_range range = *parent;

	range.va = va;
	range.last_va = last_va;

	PT_WARN_ON(last_va < va);
	PT_WARN_ON(pt_check_range(&range));

	return range;
}

/**
 * pt_init() - Initialize a pt_state on the stack
 * @range: Range pointer to embed in the state
 * @level: Table level for the state
 * @table: Pointer to the table memory at level
 *
 * Helper to initialize the on-stack pt_state from walker arguments.
 */
static __always_inline struct pt_state
pt_init(struct pt_range *range, unsigned int level, struct pt_table_p *table)
{
	struct pt_state pts = {
		.range = range,
		.table = table,
		.level = level,
	};
	return pts;
}

/**
 * pt_init_top() - Initialize a pt_state on the stack
 * @range: Range pointer to embed in the state
 *
 * The pt_state points to the top most level.
 */
static __always_inline struct pt_state pt_init_top(struct pt_range *range)
{
	return pt_init(range, range->top_level, range->top_table);
}

typedef int (*pt_level_fn_t)(struct pt_range *range, void *arg,
			     unsigned int level, struct pt_table_p *table);

/**
 * pt_descend() - Recursively invoke the walker for the lower level
 * @pts: Iteration State
 * @arg: Value to pass to the function
 * @fn: Walker function to call
 *
 * pts must point to a table item. Invoke fn as a walker on the table
 * pts points to.
 */
static __always_inline int pt_descend(struct pt_state *pts, void *arg,
				      pt_level_fn_t fn)
{
	int ret;

	if (PT_WARN_ON(!pts->table_lower))
		return -EINVAL;

	ret = (*fn)(pts->range, arg, pts->level - 1, pts->table_lower);
	return ret;
}

/**
 * pt_walk_range() - Walk over a VA range
 * @range: Range pointer
 * @fn: Walker function to call
 * @arg: Value to pass to the function
 *
 * Walk over a VA range. The caller should have done a validity check, at
 * least calling pt_check_range(), when building range. The walk will
 * start at the top most table.
 */
static __always_inline int pt_walk_range(struct pt_range *range,
					 pt_level_fn_t fn, void *arg)
{
	return fn(range, arg, range->top_level, range->top_table);
}

/*
 * pt_walk_descend() - Recursively invoke the walker for a slice of a lower
 *                     level
 * @pts: Iteration State
 * @va: Start address
 * @last_va: Last address
 * @fn: Walker function to call
 * @arg: Value to pass to the function
 *
 * With pts pointing at a table item this will descend and over a slice of the
 * lower table. The caller must ensure that va/last_va are within the table
 * item. This creates a new walk and does not alter pts or pts->range.
 */
static __always_inline int pt_walk_descend(const struct pt_state *pts,
					   pt_vaddr_t va, pt_vaddr_t last_va,
					   pt_level_fn_t fn, void *arg)
{
	struct pt_range range = pt_make_child_range(pts->range, va, last_va);

	if (PT_WARN_ON(!pt_can_have_table(pts)) ||
	    PT_WARN_ON(!pts->table_lower))
		return -EINVAL;

	return fn(&range, arg, pts->level - 1, pts->table_lower);
}

/*
 * pt_walk_descend_all() - Recursively invoke the walker for a table item
 * @parent_pts: Iteration State
 * @fn: Walker function to call
 * @arg: Value to pass to the function
 *
 * With pts pointing at a table item this will descend and over the entire lower
 * table. This creates a new walk and does not alter pts or pts->range.
 */
static __always_inline int
pt_walk_descend_all(const struct pt_state *parent_pts, pt_level_fn_t fn,
		    void *arg)
{
	unsigned int isz_lg2 = pt_table_item_lg2sz(parent_pts);

	return pt_walk_descend(parent_pts,
			       log2_set_mod(parent_pts->range->va, 0, isz_lg2),
			       log2_set_mod_max(parent_pts->range->va, isz_lg2),
			       fn, arg);
}

/**
 * pt_range_slice() - Return a range that spans indexes
 * @pts: Iteration State
 * @start_index: Starting index within pts
 * @end_index: Ending index within pts
 *
 * Create a range than spans an index range of the current table level
 * pt_state points at.
 */
static inline struct pt_range pt_range_slice(const struct pt_state *pts,
					     unsigned int start_index,
					     unsigned int end_index)
{
	unsigned int table_lg2sz = pt_table_oa_lg2sz(pts);
	pt_vaddr_t last_va;
	pt_vaddr_t va;

	va = fvalog2_set_mod(pts->range->va,
			     log2_mul(start_index, pt_table_item_lg2sz(pts)),
			     table_lg2sz);
	last_va = fvalog2_set_mod(
		pts->range->va,
		log2_mul(end_index, pt_table_item_lg2sz(pts)) - 1, table_lg2sz);
	return pt_make_child_range(pts->range, va, last_va);
}

/**
 * pt_top_memsize_lg2()
 * @common: Table
 * @top_of_table: Top of table value from _pt_top_set()
 *
 * Compute the allocation size of the top table. For PT_FEAT_DYNAMIC_TOP this
 * will compute the top size assuming the table will grow.
 */
static inline unsigned int pt_top_memsize_lg2(struct pt_common *common,
					      uintptr_t top_of_table)
{
	struct pt_range range = _pt_top_range(common, top_of_table);
	struct pt_state pts = pt_init_top(&range);
	unsigned int num_items_lg2;

	num_items_lg2 = common->max_vasz_lg2 - pt_table_item_lg2sz(&pts);
	if (range.top_level != PT_MAX_TOP_LEVEL &&
	    pt_feature(common, PT_FEAT_DYNAMIC_TOP))
		num_items_lg2 = min(num_items_lg2, pt_num_items_lg2(&pts));

	/* Round up the allocation size to the minimum alignment */
	return max(ffs_t(u64, PT_TOP_PHYS_MASK),
		   num_items_lg2 + ilog2(PT_ITEM_WORD_SIZE));
}

/**
 * pt_compute_best_pgsize() - Determine the best page size for leaf entries
 * @pgsz_bitmap: Permitted page sizes
 * @va: Starting virtual address for the leaf entry
 * @last_va: Last virtual address for the leaf entry, sets the max page size
 * @oa: Starting output address for the leaf entry
 *
 * Compute the largest page size for va, last_va, and oa together and return it
 * in lg2. The largest page size depends on the format's supported page sizes at
 * this level, and the relative alignment of the VA and OA addresses. 0 means
 * the OA cannot be stored with the provided pgsz_bitmap.
 */
static inline unsigned int pt_compute_best_pgsize(pt_vaddr_t pgsz_bitmap,
						  pt_vaddr_t va,
						  pt_vaddr_t last_va,
						  pt_oaddr_t oa)
{
	unsigned int best_pgsz_lg2;
	unsigned int pgsz_lg2;
	pt_vaddr_t len = last_va - va + 1;
	pt_vaddr_t mask;

	if (PT_WARN_ON(va >= last_va))
		return 0;

	/*
	 * Given a VA/OA pair the best page size is the largest page size
	 * where:
	 *
	 * 1) VA and OA start at the page. Bitwise this is the count of least
	 *    significant 0 bits.
	 *    This also implies that last_va/oa has the same prefix as va/oa.
	 */
	mask = va | oa;

	/*
	 * 2) The page size is not larger than the last_va (length). Since page
	 *    sizes are always power of two this can't be larger than the
	 *    largest power of two factor of the length.
	 */
	mask |= log2_to_int(vafls(len) - 1);

	best_pgsz_lg2 = vaffs(mask);

	/* Choose the highest bit <= best_pgsz_lg2 */
	if (best_pgsz_lg2 < PT_VADDR_MAX_LG2 - 1)
		pgsz_bitmap = log2_mod(pgsz_bitmap, best_pgsz_lg2 + 1);

	pgsz_lg2 = vafls(pgsz_bitmap);
	if (!pgsz_lg2)
		return 0;

	pgsz_lg2--;

	PT_WARN_ON(log2_mod(va, pgsz_lg2) != 0);
	PT_WARN_ON(oalog2_mod(oa, pgsz_lg2) != 0);
	PT_WARN_ON(va + log2_to_int(pgsz_lg2) - 1 > last_va);
	PT_WARN_ON(!log2_div_eq(va, va + log2_to_int(pgsz_lg2) - 1, pgsz_lg2));
	PT_WARN_ON(
		!oalog2_div_eq(oa, oa + log2_to_int(pgsz_lg2) - 1, pgsz_lg2));
	return pgsz_lg2;
}

#define _PT_MAKE_CALL_LEVEL(fn)                                          \
	static __always_inline int fn(struct pt_range *range, void *arg, \
				      unsigned int level,                \
				      struct pt_table_p *table)          \
	{                                                                \
		static_assert(PT_MAX_TOP_LEVEL <= 5);                    \
		if (level == 0)                                          \
			return CONCATENATE(fn, 0)(range, arg, 0, table); \
		if (level == 1 || PT_MAX_TOP_LEVEL == 1)                 \
			return CONCATENATE(fn, 1)(range, arg, 1, table); \
		if (level == 2 || PT_MAX_TOP_LEVEL == 2)                 \
			return CONCATENATE(fn, 2)(range, arg, 2, table); \
		if (level == 3 || PT_MAX_TOP_LEVEL == 3)                 \
			return CONCATENATE(fn, 3)(range, arg, 3, table); \
		if (level == 4 || PT_MAX_TOP_LEVEL == 4)                 \
			return CONCATENATE(fn, 4)(range, arg, 4, table); \
		return CONCATENATE(fn, 5)(range, arg, 5, table);         \
	}

static inline int __pt_make_level_fn_err(struct pt_range *range, void *arg,
					 unsigned int unused_level,
					 struct pt_table_p *table)
{
	static_assert(PT_MAX_TOP_LEVEL <= 5);
	return -EPROTOTYPE;
}

#define __PT_MAKE_LEVEL_FN(fn, level, descend_fn, do_fn)            \
	static inline int fn(struct pt_range *range, void *arg,     \
			     unsigned int unused_level,             \
			     struct pt_table_p *table)              \
	{                                                           \
		return do_fn(range, arg, level, table, descend_fn); \
	}

/**
 * PT_MAKE_LEVELS() - Build an unwound walker
 * @fn: Name of the walker function
 * @do_fn: Function to call at each level
 *
 * This builds a function call tree that can be fully inlined.
 * The caller must provide a function body in an __always_inline function::
 *
 *  static __always_inline int do_fn(struct pt_range *range, void *arg,
 *         unsigned int level, struct pt_table_p *table,
 *         pt_level_fn_t descend_fn)
 *
 * An inline function will be created for each table level that calls do_fn with
 * a compile time constant for level and a pointer to the next lower function.
 * This generates an optimally inlined walk where each of the functions sees a
 * constant level and can codegen the exact constants/etc for that level.
 *
 * Note this can produce a lot of code!
 */
#define PT_MAKE_LEVELS(fn, do_fn)                                             \
	__PT_MAKE_LEVEL_FN(CONCATENATE(fn, 0), 0, __pt_make_level_fn_err,     \
			   do_fn);                                            \
	__PT_MAKE_LEVEL_FN(CONCATENATE(fn, 1), 1, CONCATENATE(fn, 0), do_fn); \
	__PT_MAKE_LEVEL_FN(CONCATENATE(fn, 2), 2, CONCATENATE(fn, 1), do_fn); \
	__PT_MAKE_LEVEL_FN(CONCATENATE(fn, 3), 3, CONCATENATE(fn, 2), do_fn); \
	__PT_MAKE_LEVEL_FN(CONCATENATE(fn, 4), 4, CONCATENATE(fn, 3), do_fn); \
	__PT_MAKE_LEVEL_FN(CONCATENATE(fn, 5), 5, CONCATENATE(fn, 4), do_fn); \
	_PT_MAKE_CALL_LEVEL(fn)

#endif