src/mm.c

/*
 * Copyright 2018 The Hafnium Authors.
 *
 * Use of this source code is governed by a BSD-style
 * license that can be found in the LICENSE file or at
 * https://opensource.org/licenses/BSD-3-Clause.
 */

#include "hf/mm.h"

#include <stdatomic.h>
#include <stdint.h>

#include "hf/check.h"
#include "hf/dlog.h"
#include "hf/layout.h"
#include "hf/plat/console.h"
#include "hf/static_assert.h"

/**
 * This file has functions for managing the level 1 and 2 page tables used by
 * Hafnium. There is a level 1 mapping used by Hafnium itself to access memory,
 * and then a level 2 mapping per VM. The design assumes that all page tables
 * contain only 1-1 mappings, aligned on the block boundaries.
 */

/*
 * For stage 2, the input is an intermediate physical addresses rather than a
 * virtual address so:
 */
static_assert(
	sizeof(ptable_addr_t) == sizeof(uintpaddr_t),
	"Currently, the same code manages the stage 1 and stage 2 page tables "
	"which only works if the virtual and intermediate physical addresses "
	"are the same size. It looks like that assumption might not be holding "
	"so we need to check that everything is going to be ok.");

static struct mm_ptable ptable;
static struct spinlock ptable_lock;

static bool mm_stage2_invalidate = false;

/**
 * After calling this function, modifications to stage-2 page tables will use
 * break-before-make and invalidate the TLB for the affected range.
 */
void mm_vm_enable_invalidation(void)
{
	mm_stage2_invalidate = true;
}

/**
 * Get the page table from the physical address.
 */
static struct mm_page_table *mm_page_table_from_pa(paddr_t pa)
{
	return ptr_from_va(va_from_pa(pa));
}

/**
 * Rounds an address down to a page boundary.
 */
static ptable_addr_t mm_round_down_to_page(ptable_addr_t addr)
{
	return addr & ~((ptable_addr_t)(PAGE_SIZE - 1));
}

/**
 * Rounds an address up to a page boundary.
 */
static ptable_addr_t mm_round_up_to_page(ptable_addr_t addr)
{
	return mm_round_down_to_page(addr + PAGE_SIZE - 1);
}

/**
 * Calculates the size of the address space represented by a page table entry at
 * the given level.
 */
static size_t mm_entry_size(uint8_t level)
{
	return UINT64_C(1) << (PAGE_BITS + level * PAGE_LEVEL_BITS);
}

/**
 * Gets the address of the start of the next block of the given size. The size
 * must be a power of two.
 */
static ptable_addr_t mm_start_of_next_block(ptable_addr_t addr,
					    size_t block_size)
{
	return (addr + block_size) & ~(block_size - 1);
}

/**
 * Gets the physical address of the start of the next block of the given size.
 * The size must be a power of two.
 */
static paddr_t mm_pa_start_of_next_block(paddr_t pa, size_t block_size)
{
	return pa_init((pa_addr(pa) + block_size) & ~(block_size - 1));
}

/**
 * For a given address, calculates the maximum (plus one) address that can be
 * represented by the same table at the given level.
 */
static ptable_addr_t mm_level_end(ptable_addr_t addr, uint8_t level)
{
	size_t offset = PAGE_BITS + (level + 1) * PAGE_LEVEL_BITS;

	return ((addr >> offset) + 1) << offset;
}

/**
 * For a given address, calculates the index at which its entry is stored in a
 * table at the given level.
 */
static size_t mm_index(ptable_addr_t addr, uint8_t level)
{
	ptable_addr_t v = addr >> (PAGE_BITS + level * PAGE_LEVEL_BITS);

	return v & ((UINT64_C(1) << PAGE_LEVEL_BITS) - 1);
}

/**
 * Allocates a new page table.
 */
static struct mm_page_table *mm_alloc_page_tables(size_t count,
						  struct mpool *ppool)
{
	if (count == 1) {
		return mpool_alloc(ppool);
	}

	return mpool_alloc_contiguous(ppool, count, count);
}

/**
 * Returns the maximum level in the page table given the flags.
 */
static uint8_t mm_max_level(int flags)
{
	return (flags & MM_FLAG_STAGE1) ? arch_mm_stage1_max_level()
					: arch_mm_stage2_max_level();
}

/**
 * Returns the number of root-level tables given the flags.
 */
static uint8_t mm_root_table_count(int flags)
{
	return (flags & MM_FLAG_STAGE1) ? arch_mm_stage1_root_table_count()
					: arch_mm_stage2_root_table_count();
}

/**
 * Invalidates the TLB for the given address range.
 */
static void mm_invalidate_tlb(ptable_addr_t begin, ptable_addr_t end, int flags)
{
	if (flags & MM_FLAG_STAGE1) {
		arch_mm_invalidate_stage1_range(va_init(begin), va_init(end));
	} else {
		arch_mm_invalidate_stage2_range(ipa_init(begin), ipa_init(end));
	}
}

/**
 * Frees all page-table-related memory associated with the given pte at the
 * given level, including any subtables recursively.
 */
static void mm_free_page_pte(pte_t pte, uint8_t level, struct mpool *ppool)
{
	struct mm_page_table *table;
	uint64_t i;

	if (!arch_mm_pte_is_table(pte, level)) {
		return;
	}

	/* Recursively free any subtables. */
	table = mm_page_table_from_pa(arch_mm_table_from_pte(pte, level));
	for (i = 0; i < MM_PTE_PER_PAGE; ++i) {
		mm_free_page_pte(table->entries[i], level - 1, ppool);
	}

	/* Free the table itself. */
	mpool_free(ppool, table);
}

/**
 * Returns the first address which cannot be encoded in page tables given by
 * `flags`. It is the exclusive end of the address space created by the tables.
 */
ptable_addr_t mm_ptable_addr_space_end(int flags)
{
	return mm_root_table_count(flags) *
	       mm_entry_size(mm_max_level(flags) + 1);
}

/**
 * Initialises the given page table.
 */
bool mm_ptable_init(struct mm_ptable *t, int flags, struct mpool *ppool)
{
	uint8_t i;
	size_t j;
	struct mm_page_table *tables;
	uint8_t root_table_count = mm_root_table_count(flags);

	tables = mm_alloc_page_tables(root_table_count, ppool);
	if (tables == NULL) {
		return false;
	}

	for (i = 0; i < root_table_count; i++) {
		for (j = 0; j < MM_PTE_PER_PAGE; j++) {
			tables[i].entries[j] =
				arch_mm_absent_pte(mm_max_level(flags));
		}
	}

	/*
	 * TODO: halloc could return a virtual or physical address if mm not
	 * enabled?
	 */
	t->root = pa_init((uintpaddr_t)tables);

	return true;
}

/**
 * Frees all memory associated with the give page table.
 */
static void mm_ptable_fini(struct mm_ptable *t, int flags, struct mpool *ppool)
{
	struct mm_page_table *tables = mm_page_table_from_pa(t->root);
	uint8_t level = mm_max_level(flags);
	uint8_t root_table_count = mm_root_table_count(flags);
	uint8_t i;
	uint64_t j;

	for (i = 0; i < root_table_count; ++i) {
		for (j = 0; j < MM_PTE_PER_PAGE; ++j) {
			mm_free_page_pte(tables[i].entries[j], level, ppool);
		}
	}

	mpool_add_chunk(ppool, tables,
			sizeof(struct mm_page_table) * root_table_count);
}

/**
 * Replaces a page table entry with the given value. If both old and new values
 * are valid, it performs a break-before-make sequence where it first writes an
 * invalid value to the PTE, flushes the TLB, then writes the actual new value.
 * This is to prevent cases where CPUs have different 'valid' values in their
 * TLBs, which may result in issues for example in cache coherency.
 */
static void mm_replace_entry(ptable_addr_t begin, pte_t *pte, pte_t new_pte,
			     uint8_t level, int flags, struct mpool *ppool)
{
	pte_t v = *pte;

	/*
	 * We need to do the break-before-make sequence if both values are
	 * present and the TLB is being invalidated.
	 */
	if (((flags & MM_FLAG_STAGE1) || mm_stage2_invalidate) &&
	    arch_mm_pte_is_valid(v, level) &&
	    arch_mm_pte_is_valid(new_pte, level)) {
		*pte = arch_mm_absent_pte(level);
		mm_invalidate_tlb(begin, begin + mm_entry_size(level), flags);
	}

	/* Assign the new pte. */
	*pte = new_pte;

	/* Free pages that aren't in use anymore. */
	mm_free_page_pte(v, level, ppool);
}

/**
 * Populates the provided page table entry with a reference to another table if
 * needed, that is, if it does not yet point to another table.
 *
 * Returns a pointer to the table the entry now points to.
 */
static struct mm_page_table *mm_populate_table_pte(ptable_addr_t begin,
						   pte_t *pte, uint8_t level,
						   int flags,
						   struct mpool *ppool)
{
	struct mm_page_table *ntable;
	pte_t v = *pte;
	pte_t new_pte;
	size_t i;
	size_t inc;
	uint8_t level_below = level - 1;

	/* Just return pointer to table if it's already populated. */
	if (arch_mm_pte_is_table(v, level)) {
		return mm_page_table_from_pa(arch_mm_table_from_pte(v, level));
	}

	/* Allocate a new table. */
	ntable = mm_alloc_page_tables(1, ppool);
	if (ntable == NULL) {
		dlog_error("Failed to allocate memory for page table\n");
		return NULL;
	}

	/* Determine template for new pte and its increment. */
	if (arch_mm_pte_is_block(v, level)) {
		inc = mm_entry_size(level_below);
		new_pte = arch_mm_block_pte(level_below,
					    arch_mm_block_from_pte(v, level),
					    arch_mm_pte_attrs(v, level));
	} else {
		inc = 0;
		new_pte = arch_mm_absent_pte(level_below);
	}

	/* Initialise entries in the new table. */
	for (i = 0; i < MM_PTE_PER_PAGE; i++) {
		ntable->entries[i] = new_pte;
		new_pte += inc;
	}

	/* Ensure initialisation is visible before updating the pte. */
	atomic_thread_fence(memory_order_release);

	/* Replace the pte entry, doing a break-before-make if needed. */
	mm_replace_entry(begin, pte,
			 arch_mm_table_pte(level, pa_init((uintpaddr_t)ntable)),
			 level, flags, ppool);

	return ntable;
}

/**
 * Updates the page table at the given level to map the given address range to a
 * physical range using the provided (architecture-specific) attributes. Or if
 * MM_FLAG_UNMAP is set, unmap the given range instead.
 *
 * This function calls itself recursively if it needs to update additional
 * levels, but the recursion is bound by the maximum number of levels in a page
 * table.
 */
static bool mm_map_level(ptable_addr_t begin, ptable_addr_t end, paddr_t pa,
			 uint64_t attrs, struct mm_page_table *table,
			 uint8_t level, int flags, struct mpool *ppool)
{
	pte_t *pte = &table->entries[mm_index(begin, level)];
	ptable_addr_t level_end = mm_level_end(begin, level);
	size_t entry_size = mm_entry_size(level);
	bool commit = flags & MM_FLAG_COMMIT;
	bool unmap = flags & MM_FLAG_UNMAP;

	/* Cap end so that we don't go over the current level max. */
	if (end > level_end) {
		end = level_end;
	}

	/* Fill each entry in the table. */
	while (begin < end) {
		if (unmap ? !arch_mm_pte_is_present(*pte, level)
			  : arch_mm_pte_is_block(*pte, level) &&
				    arch_mm_pte_attrs(*pte, level) == attrs) {
			/*
			 * If the entry is already mapped with the right
			 * attributes, or already absent in the case of
			 * unmapping, no need to do anything; carry on to the
			 * next entry.
			 */
		} else if ((end - begin) >= entry_size &&
			   (unmap || arch_mm_is_block_allowed(level)) &&
			   (begin & (entry_size - 1)) == 0) {
			/*
			 * If the entire entry is within the region we want to
			 * map, map/unmap the whole entry.
			 */
			if (commit) {
				pte_t new_pte =
					unmap ? arch_mm_absent_pte(level)
					      : arch_mm_block_pte(level, pa,
								  attrs);
				mm_replace_entry(begin, pte, new_pte, level,
						 flags, ppool);
			}
		} else {
			/*
			 * If the entry is already a subtable get it; otherwise
			 * replace it with an equivalent subtable and get that.
			 */
			struct mm_page_table *nt = mm_populate_table_pte(
				begin, pte, level, flags, ppool);
			if (nt == NULL) {
				return false;
			}

			/*
			 * Recurse to map/unmap the appropriate entries within
			 * the subtable.
			 */
			if (!mm_map_level(begin, end, pa, attrs, nt, level - 1,
					  flags, ppool)) {
				return false;
			}
		}

		begin = mm_start_of_next_block(begin, entry_size);
		pa = mm_pa_start_of_next_block(pa, entry_size);
		pte++;
	}

	return true;
}

/**
 * Updates the page table from the root to map the given address range to a
 * physical range using the provided (architecture-specific) attributes. Or if
 * MM_FLAG_UNMAP is set, unmap the given range instead.
 */
static bool mm_map_root(struct mm_ptable *t, ptable_addr_t begin,
			ptable_addr_t end, uint64_t attrs, uint8_t root_level,
			int flags, struct mpool *ppool)
{
	size_t root_table_size = mm_entry_size(root_level);
	struct mm_page_table *table =
		&mm_page_table_from_pa(t->root)[mm_index(begin, root_level)];

	while (begin < end) {
		if (!mm_map_level(begin, end, pa_init(begin), attrs, table,
				  root_level - 1, flags, ppool)) {
			return false;
		}
		begin = mm_start_of_next_block(begin, root_table_size);
		table++;
	}

	return true;
}

/**
 * Updates the given table such that the given physical address range is mapped
 * or not mapped into the address space with the architecture-agnostic mode
 * provided. Only commits the change if MM_FLAG_COMMIT is set.
 */
static bool mm_ptable_identity_map(struct mm_ptable *t, paddr_t pa_begin,
				   paddr_t pa_end, uint64_t attrs, int flags,
				   struct mpool *ppool)
{
	uint8_t root_level = mm_max_level(flags) + 1;
	ptable_addr_t ptable_end = mm_ptable_addr_space_end(flags);
	ptable_addr_t end = mm_round_up_to_page(pa_addr(pa_end));
	ptable_addr_t begin = pa_addr(arch_mm_clear_pa(pa_begin));

	/*
	 * Assert condition to communicate the API constraint of mm_max_level(),
	 * that isn't encoded in the types, to the static analyzer.
	 */
	CHECK(root_level >= 2);

	/* Cap end to stay within the bounds of the page table. */
	if (end > ptable_end) {
		end = ptable_end;
	}

	if (!mm_map_root(t, begin, end, attrs, root_level, flags, ppool)) {
		return false;
	}

	/* Invalidate the TLB. */
	if ((flags & MM_FLAG_COMMIT) &&
	    ((flags & MM_FLAG_STAGE1) || mm_stage2_invalidate)) {
		mm_invalidate_tlb(begin, end, flags);
	}

	return true;
}

/*
 * Prepares the given page table for the given address mapping such that it
 * will be able to commit the change without failure. It does so by ensuring
 * the smallest granularity needed is available. This remains valid provided
 * subsequent operations do not decrease the granularity.
 *
 * In particular, multiple calls to this function will result in the
 * corresponding calls to commit the changes to succeed.
 */
static bool mm_ptable_identity_prepare(struct mm_ptable *t, paddr_t pa_begin,
				       paddr_t pa_end, uint64_t attrs,
				       int flags, struct mpool *ppool)
{
	flags &= ~MM_FLAG_COMMIT;
	return mm_ptable_identity_map(t, pa_begin, pa_end, attrs, flags, ppool);
}

/**
 * Commits the given address mapping to the page table assuming the operation
 * cannot fail. `mm_ptable_identity_prepare` must used correctly before this to
 * ensure this condition.
 *
 * Without the table being properly prepared, the commit may only partially
 * complete if it runs out of memory resulting in an inconsistent state that
 * isn't handled.
 *
 * Since the non-failure assumtion is used in the reasoning about the atomicity
 * of higher level memory operations, any detected violations result in a panic.
 *
 * TODO: remove ppool argument to be sure no changes are made.
 */
static void mm_ptable_identity_commit(struct mm_ptable *t, paddr_t pa_begin,
				      paddr_t pa_end, uint64_t attrs, int flags,
				      struct mpool *ppool)
{
	CHECK(mm_ptable_identity_map(t, pa_begin, pa_end, attrs,
				     flags | MM_FLAG_COMMIT, ppool));
}

/**
 * Updates the given table such that the given physical address range is mapped
 * or not mapped into the address space with the architecture-agnostic mode
 * provided.
 *
 * The page table is updated using the separate prepare and commit stages so
 * that, on failure, a partial update of the address space cannot happen. The
 * table may be left with extra internal tables but the address space is
 * unchanged.
 */
static bool mm_ptable_identity_update(struct mm_ptable *t, paddr_t pa_begin,
				      paddr_t pa_end, uint64_t attrs, int flags,
				      struct mpool *ppool)
{
	if (!mm_ptable_identity_prepare(t, pa_begin, pa_end, attrs, flags,
					ppool)) {
		return false;
	}

	mm_ptable_identity_commit(t, pa_begin, pa_end, attrs, flags, ppool);

	return true;
}

/**
 * Writes the given table to the debug log, calling itself recursively to
 * write sub-tables.
 */
static void mm_dump_table_recursive(struct mm_page_table *table, uint8_t level,
				    int max_level)
{
	uint64_t i;

	for (i = 0; i < MM_PTE_PER_PAGE; i++) {
		if (!arch_mm_pte_is_present(table->entries[i], level)) {
			continue;
		}

		dlog("%*s%x: %x\n", 4 * (max_level - level), "", i,
		     table->entries[i]);

		if (arch_mm_pte_is_table(table->entries[i], level)) {
			mm_dump_table_recursive(
				mm_page_table_from_pa(arch_mm_table_from_pte(
					table->entries[i], level)),
				level - 1, max_level);
		}
	}
}

/**
 * Writes the given table to the debug log.
 */
static void mm_ptable_dump(struct mm_ptable *t, int flags)
{
	struct mm_page_table *tables = mm_page_table_from_pa(t->root);
	uint8_t max_level = mm_max_level(flags);
	uint8_t root_table_count = mm_root_table_count(flags);
	uint8_t i;

	for (i = 0; i < root_table_count; ++i) {
		mm_dump_table_recursive(&tables[i], max_level, max_level);
	}
}

/**
 * Given the table PTE entries all have identical attributes, returns the single
 * entry with which it can be replaced. Note that the table PTE will no longer
 * be valid after calling this function as the table may have been freed.
 *
 * If the table is freed, the memory is freed directly rather than calling
 * `mm_free_page_pte()` as it is known to not have subtables.
 */
static pte_t mm_merge_table_pte(pte_t table_pte, uint8_t level,
				struct mpool *ppool)
{
	struct mm_page_table *table;
	uint64_t block_attrs;
	uint64_t table_attrs;
	uint64_t combined_attrs;
	paddr_t block_address;

	table = mm_page_table_from_pa(arch_mm_table_from_pte(table_pte, level));

	if (!arch_mm_pte_is_present(table->entries[0], level - 1)) {
		/* Free the table and return an absent entry. */
		mpool_free(ppool, table);
		return arch_mm_absent_pte(level);
	}

	/* Might not be possible to merge the table into a single block. */
	if (!arch_mm_is_block_allowed(level)) {
		return table_pte;
	}

	/* Replace table with a single block, with equivalent attributes. */
	block_attrs = arch_mm_pte_attrs(table->entries[0], level - 1);
	table_attrs = arch_mm_pte_attrs(table_pte, level);
	combined_attrs =
		arch_mm_combine_table_entry_attrs(table_attrs, block_attrs);
	block_address = arch_mm_block_from_pte(table->entries[0], level - 1);

	/* Free the table and return a block. */
	mpool_free(ppool, table);
	return arch_mm_block_pte(level, block_address, combined_attrs);
}

/**
 * Defragments the given PTE by recursively replacing any tables with blocks or
 * absent entries where possible.
 */
static pte_t mm_ptable_defrag_entry(pte_t entry, uint8_t level,
				    struct mpool *ppool)
{
	struct mm_page_table *table;
	uint64_t i;
	bool mergeable;
	bool base_present;
	uint64_t base_attrs;

	if (!arch_mm_pte_is_table(entry, level)) {
		return entry;
	}

	table = mm_page_table_from_pa(arch_mm_table_from_pte(entry, level));

	/* Defrag the first entry in the table and use it as the base entry. */
	static_assert(MM_PTE_PER_PAGE >= 1, "There must be at least one PTE.");
	table->entries[0] =
		mm_ptable_defrag_entry(table->entries[0], level - 1, ppool);
	base_present = arch_mm_pte_is_present(table->entries[0], level - 1);
	base_attrs = arch_mm_pte_attrs(table->entries[0], level - 1);

	/*
	 * Defrag the remaining entries in the table and check whether they are
	 * compatible with the base entry meaning the table can be merged into a
	 * block entry. It assumes addresses are contiguous due to identity
	 * mapping.
	 */
	mergeable = true;
	for (i = 1; i < MM_PTE_PER_PAGE; ++i) {
		bool present;

		table->entries[i] = mm_ptable_defrag_entry(table->entries[i],
							   level - 1, ppool);
		present = arch_mm_pte_is_present(table->entries[i], level - 1);

		if (present != base_present) {
			mergeable = false;
			continue;
		}

		if (!present) {
			continue;
		}

		if (!arch_mm_pte_is_block(table->entries[i], level - 1)) {
			mergeable = false;
			continue;
		}

		if (arch_mm_pte_attrs(table->entries[i], level - 1) !=
		    base_attrs) {
			mergeable = false;
			continue;
		}
	}

	if (mergeable) {
		return mm_merge_table_pte(entry, level, ppool);
	}

	return entry;
}

/**
 * Defragments the given page table by converting page table references to
 * blocks whenever possible.
 */
static void mm_ptable_defrag(struct mm_ptable *t, int flags,
			     struct mpool *ppool)
{
	struct mm_page_table *tables = mm_page_table_from_pa(t->root);
	uint8_t level = mm_max_level(flags);
	uint8_t root_table_count = mm_root_table_count(flags);
	uint8_t i;
	uint64_t j;

	/*
	 * Loop through each entry in the table. If it points to another table,
	 * check if that table can be replaced by a block or an absent entry.
	 */
	for (i = 0; i < root_table_count; ++i) {
		for (j = 0; j < MM_PTE_PER_PAGE; ++j) {
			tables[i].entries[j] = mm_ptable_defrag_entry(
				tables[i].entries[j], level, ppool);
		}
	}
}

/**
 * Gets the attributes applied to the given range of stage-2 addresses at the
 * given level.
 *
 * The `got_attrs` argument is initially passed as false until `attrs` contains
 * attributes of the memory region at which point it is passed as true.
 *
 * The value returned in `attrs` is only valid if the function returns true.
 *
 * Returns true if the whole range has the same attributes and false otherwise.
 */
static bool mm_ptable_get_attrs_level(struct mm_page_table *table,
				      ptable_addr_t begin, ptable_addr_t end,
				      uint8_t level, bool got_attrs,
				      uint64_t *attrs)
{
	pte_t *pte = &table->entries[mm_index(begin, level)];
	ptable_addr_t level_end = mm_level_end(begin, level);
	size_t entry_size = mm_entry_size(level);

	/* Cap end so that we don't go over the current level max. */
	if (end > level_end) {
		end = level_end;
	}

	/* Check that each entry is owned. */
	while (begin < end) {
		if (arch_mm_pte_is_table(*pte, level)) {
			if (!mm_ptable_get_attrs_level(
				    mm_page_table_from_pa(
					    arch_mm_table_from_pte(*pte,
								   level)),
				    begin, end, level - 1, got_attrs, attrs)) {
				return false;
			}
			got_attrs = true;
		} else {
			if (!got_attrs) {
				*attrs = arch_mm_pte_attrs(*pte, level);
				got_attrs = true;
			} else if (arch_mm_pte_attrs(*pte, level) != *attrs) {
				return false;
			}
		}

		begin = mm_start_of_next_block(begin, entry_size);
		pte++;
	}

	/* The entry is a valid block. */
	return got_attrs;
}

/**
 * Gets the attributes applies to the given range of addresses in the stage-2
 * table.
 *
 * The value returned in `attrs` is only valid if the function returns true.
 *
 * Returns true if the whole range has the same attributes and false otherwise.
 */
static bool mm_vm_get_attrs(struct mm_ptable *t, ptable_addr_t begin,
			    ptable_addr_t end, uint64_t *attrs)
{
	int flags = 0;
	uint8_t max_level = mm_max_level(flags);
	uint8_t root_level = max_level + 1;
	size_t root_table_size = mm_entry_size(root_level);
	ptable_addr_t ptable_end =
		mm_root_table_count(flags) * mm_entry_size(root_level);
	struct mm_page_table *table;
	bool got_attrs = false;

	begin = mm_round_down_to_page(begin);
	end = mm_round_up_to_page(end);

	/* Fail if the addresses are out of range. */
	if (end > ptable_end) {
		return false;
	}

	table = &mm_page_table_from_pa(t->root)[mm_index(begin, root_level)];
	while (begin < end) {
		if (!mm_ptable_get_attrs_level(table, begin, end, max_level,
					       got_attrs, attrs)) {
			return false;
		}

		got_attrs = true;
		begin = mm_start_of_next_block(begin, root_table_size);
		table++;
	}

	return got_attrs;
}

bool mm_vm_init(struct mm_ptable *t, struct mpool *ppool)
{
	return mm_ptable_init(t, 0, ppool);
}

void mm_vm_fini(struct mm_ptable *t, struct mpool *ppool)
{
	mm_ptable_fini(t, 0, ppool);
}

/**
 * Selects flags to pass to the page table manipulation operation based on the
 * mapping mode.
 */
static int mm_mode_to_flags(uint32_t mode)
{
	if ((mode & MM_MODE_UNMAPPED_MASK) == MM_MODE_UNMAPPED_MASK) {
		return MM_FLAG_UNMAP;
	}

	return 0;
}

/**
 * See `mm_ptable_identity_prepare`.
 *
 * This must be called before `mm_vm_identity_commit` for the same mapping.
 *
 * Returns true on success, or false if the update would fail.
 */
bool mm_vm_identity_prepare(struct mm_ptable *t, paddr_t begin, paddr_t end,
			    uint32_t mode, struct mpool *ppool)
{
	int flags = mm_mode_to_flags(mode);

	return mm_ptable_identity_prepare(t, begin, end,
					  arch_mm_mode_to_stage2_attrs(mode),
					  flags, ppool);
}

/**
 * See `mm_ptable_identity_commit`.
 *
 * `mm_vm_identity_prepare` must be called before this for the same mapping.
 */
void mm_vm_identity_commit(struct mm_ptable *t, paddr_t begin, paddr_t end,
			   uint32_t mode, struct mpool *ppool, ipaddr_t *ipa)
{
	int flags = mm_mode_to_flags(mode);

	mm_ptable_identity_commit(t, begin, end,
				  arch_mm_mode_to_stage2_attrs(mode), flags,
				  ppool);

	if (ipa != NULL) {
		*ipa = ipa_from_pa(begin);
	}
}

/**
 * Updates a VM's page table such that the given physical address range is
 * mapped in the address space at the corresponding address range in the
 * architecture-agnostic mode provided.
 *
 * mm_vm_defrag should always be called after a series of page table updates,
 * whether they succeed or fail. This is because on failure extra page table
 * entries may have been allocated and then not used, while on success it may be
 * possible to compact the page table by merging several entries into a block.
 *
 * Returns true on success, or false if the update failed and no changes were
 * made.
 */
bool mm_vm_identity_map(struct mm_ptable *t, paddr_t begin, paddr_t end,
			uint32_t mode, struct mpool *ppool, ipaddr_t *ipa)
{
	int flags = mm_mode_to_flags(mode);
	bool success = mm_ptable_identity_update(
		t, begin, end, arch_mm_mode_to_stage2_attrs(mode), flags,
		ppool);

	if (success && ipa != NULL) {
		*ipa = ipa_from_pa(begin);
	}

	return success;
}

/**
 * Updates the VM's table such that the given physical address range has no
 * connection to the VM.
 */
bool mm_vm_unmap(struct mm_ptable *t, paddr_t begin, paddr_t end,
		 struct mpool *ppool)
{
	uint32_t mode = MM_MODE_UNMAPPED_MASK;

	return mm_vm_identity_map(t, begin, end, mode, ppool, NULL);
}

/**
 * Write the given page table of a VM to the debug log.
 */
void mm_vm_dump(struct mm_ptable *t)
{
	mm_ptable_dump(t, 0);
}

/**
 * Defragments the VM page table.
 */
void mm_vm_defrag(struct mm_ptable *t, struct mpool *ppool)
{
	mm_ptable_defrag(t, 0, ppool);
}

/**
 * Gets the mode of the given range of intermediate physical addresses if they
 * are mapped with the same mode.
 *
 * Returns true if the range is mapped with the same mode and false otherwise.
 */
bool mm_vm_get_mode(struct mm_ptable *t, ipaddr_t begin, ipaddr_t end,
		    uint32_t *mode)
{
	uint64_t attrs;
	bool ret;

	ret = mm_vm_get_attrs(t, ipa_addr(begin), ipa_addr(end), &attrs);
	if (ret) {
		*mode = arch_mm_stage2_attrs_to_mode(attrs);
	}

	return ret;
}

static struct mm_stage1_locked mm_stage1_lock_unsafe(void)
{
	return (struct mm_stage1_locked){.ptable = &ptable};
}

struct mm_stage1_locked mm_lock_stage1(void)
{
	sl_lock(&ptable_lock);
	return mm_stage1_lock_unsafe();
}

void mm_unlock_stage1(struct mm_stage1_locked *lock)
{
	CHECK(lock->ptable == &ptable);
	sl_unlock(&ptable_lock);
	lock->ptable = NULL;
}

/**
 * Updates the hypervisor page table such that the given physical address range
 * is mapped into the address space at the corresponding address range in the
 * architecture-agnostic mode provided.
 */
void *mm_identity_map(struct mm_stage1_locked stage1_locked, paddr_t begin,
		      paddr_t end, uint32_t mode, struct mpool *ppool)
{
	int flags = MM_FLAG_STAGE1 | mm_mode_to_flags(mode);

	if (mm_ptable_identity_update(stage1_locked.ptable, begin, end,
				      arch_mm_mode_to_stage1_attrs(mode), flags,
				      ppool)) {
		return ptr_from_va(va_from_pa(begin));
	}

	return NULL;
}

/**
 * Updates the hypervisor table such that the given physical address range is
 * not mapped in the address space.
 */
bool mm_unmap(struct mm_stage1_locked stage1_locked, paddr_t begin, paddr_t end,
	      struct mpool *ppool)
{
	uint32_t mode = MM_MODE_UNMAPPED_MASK;

	return mm_identity_map(stage1_locked, begin, end, mode, ppool);
}

/**
 * Defragments the hypervisor page table.
 */
void mm_defrag(struct mm_stage1_locked stage1_locked, struct mpool *ppool)
{
	mm_ptable_defrag(stage1_locked.ptable, MM_FLAG_STAGE1, ppool);
}

/**
 * Initialises memory management for the hypervisor itself.
 */
bool mm_init(struct mpool *ppool)
{
	/* Locking is not enabled yet so fake it, */
	struct mm_stage1_locked stage1_locked = mm_stage1_lock_unsafe();

	dlog_info("text: %#x - %#x\n", pa_addr(layout_text_begin()),
		  pa_addr(layout_text_end()));
	dlog_info("rodata: %#x - %#x\n", pa_addr(layout_rodata_begin()),
		  pa_addr(layout_rodata_end()));
	dlog_info("data: %#x - %#x\n", pa_addr(layout_data_begin()),
		  pa_addr(layout_data_end()));

	if (!mm_ptable_init(&ptable, MM_FLAG_STAGE1, ppool)) {
		dlog_error("Unable to allocate memory for page table.\n");
		return false;
	}

	/* Let console driver map pages for itself. */
	plat_console_mm_init(stage1_locked, ppool);

	/* Map each section. */
	mm_identity_map(stage1_locked, layout_text_begin(), layout_text_end(),
			MM_MODE_X, ppool);

	mm_identity_map(stage1_locked, layout_rodata_begin(),
			layout_rodata_end(), MM_MODE_R, ppool);

	mm_identity_map(stage1_locked, layout_data_begin(), layout_data_end(),
			MM_MODE_R | MM_MODE_W, ppool);

	return arch_mm_init(ptable.root);
}