core/mm/pgt_cache.c

// SPDX-License-Identifier: BSD-2-Clause
/*
 * Copyright (c) 2016, 2022 Linaro Limited
 */

#include <assert.h>
#include <kernel/mutex.h>
#include <kernel/spinlock.h>
#include <kernel/tee_misc.h>
#include <kernel/user_mode_ctx.h>
#include <mm/core_memprot.h>
#include <mm/core_mmu.h>
#include <mm/pgt_cache.h>
#include <mm/tee_pager.h>
#include <stdlib.h>
#include <trace.h>
#include <util.h>

/*
 * With pager enabled we allocate page table from the pager.
 *
 * For LPAE each page table is a complete page which is allocated and freed
 * using the interface provided by the pager.
 *
 * For compat v7 page tables there's room for four page table in one page
 * so we need to keep track of how much of an allocated page is used. When
 * a page is completely unused it's returned to the pager.
 *
 * With pager disabled we have a static allocation of page tables instead.
 *
 * In all cases we limit the number of active page tables to
 * PGT_CACHE_SIZE.  This pool of page tables are shared between all
 * threads. In case a thread can't allocate the needed number of pager
 * tables it will release all its current tables and wait for some more to
 * be freed. A threads allocated tables are freed each time a TA is
 * unmapped so each thread should be able to allocate the needed tables in
 * turn if needed.
 */

#if defined(CFG_CORE_PREALLOC_EL0_TBLS) || \
	(defined(CFG_WITH_PAGER) && !defined(CFG_WITH_LPAE))
struct pgt_parent {
	size_t num_used;
	struct pgt_cache pgt_cache;
#if defined(CFG_CORE_PREALLOC_EL0_TBLS)
	tee_mm_entry_t *mm;
	SLIST_ENTRY(pgt_parent) link;
#endif
};
#endif

#if defined(CFG_CORE_PREALLOC_EL0_TBLS)

/*
 * Pick something large enough that tee_mm_alloc() doesn't have to be
 * called for each needed translation table.
 */
#define PGT_PARENT_SIZE		(4 * SMALL_PAGE_SIZE)
#define PGT_PARENT_TBL_COUNT	(PGT_PARENT_SIZE / PGT_SIZE)

SLIST_HEAD(pgt_parent_list, pgt_parent);
static struct pgt_parent_list parent_list = SLIST_HEAD_INITIALIZER(parent_list);
static unsigned int parent_spinlock = SPINLOCK_UNLOCK;

static void free_pgt(struct pgt *pgt)
{
	struct pgt_parent *parent = NULL;
	uint32_t exceptions = 0;

	exceptions = cpu_spin_lock_xsave(&parent_spinlock);

	assert(pgt && pgt->parent);
	parent = pgt->parent;
	assert(parent->num_used <= PGT_PARENT_TBL_COUNT &&
	       parent->num_used > 0);
	if (parent->num_used == PGT_PARENT_TBL_COUNT)
		SLIST_INSERT_HEAD(&parent_list, parent, link);
	parent->num_used--;

	if (!parent->num_used && SLIST_NEXT(SLIST_FIRST(&parent_list), link)) {
		/*
		 * If this isn't the last pgt_parent with free entries we
		 * can free this.
		 */
		SLIST_REMOVE(&parent_list, parent, pgt_parent, link);
		tee_mm_free(parent->mm);
		free(parent);
	} else {
		SLIST_INSERT_HEAD(&parent->pgt_cache, pgt, link);
		pgt->vabase = 0;
		pgt->populated = false;
	}

	cpu_spin_unlock_xrestore(&parent_spinlock, exceptions);
}

static struct pgt_parent *alloc_pgt_parent(void)
{
	struct pgt_parent *parent = NULL;
	struct pgt *pgt = NULL;
	uint8_t *tbl = NULL;
	size_t sz = 0;
	size_t n = 0;

	sz = sizeof(*parent) + sizeof(*pgt) * PGT_PARENT_TBL_COUNT;
	parent = calloc(1, sz);
	if (!parent)
		return NULL;
	parent->mm = tee_mm_alloc(&tee_mm_sec_ddr, PGT_PARENT_SIZE);
	if (!parent->mm) {
		free(parent);
		return NULL;
	}
	tbl = phys_to_virt(tee_mm_get_smem(parent->mm), MEM_AREA_TA_RAM,
			   PGT_PARENT_SIZE);
	assert(tbl); /* "can't fail" */

	SLIST_INIT(&parent->pgt_cache);
	pgt = (struct pgt *)(parent + 1);
	for (n = 0; n < PGT_PARENT_TBL_COUNT; n++) {
		pgt[n].parent = parent;
		pgt[n].tbl = tbl + n * PGT_SIZE;
		SLIST_INSERT_HEAD(&parent->pgt_cache, pgt + n, link);
	}

	return parent;
}

static struct pgt *alloc_pgt(vaddr_t vabase)
{
	struct pgt_parent *parent = NULL;
	uint32_t exceptions = 0;
	struct pgt *pgt = NULL;

	exceptions = cpu_spin_lock_xsave(&parent_spinlock);

	parent = SLIST_FIRST(&parent_list);
	if (!parent) {
		parent = alloc_pgt_parent();
		if (!parent)
			goto out;

		SLIST_INSERT_HEAD(&parent_list, parent, link);
	}

	pgt = SLIST_FIRST(&parent->pgt_cache);
	SLIST_REMOVE_HEAD(&parent->pgt_cache, link);
	parent->num_used++;
	assert(pgt && parent->num_used <= PGT_PARENT_TBL_COUNT);
	if (parent->num_used == PGT_PARENT_TBL_COUNT)
		SLIST_REMOVE_HEAD(&parent_list, link);

	pgt->vabase = vabase;
out:
	cpu_spin_unlock_xrestore(&parent_spinlock, exceptions);
	return pgt;
}

static bool pgt_entry_matches(struct pgt *p, vaddr_t begin, vaddr_t last)
{
	if (!p)
		return false;
	if (last <= begin)
		return false;
	return core_is_buffer_inside(p->vabase, CORE_MMU_PGDIR_SIZE, begin,
				     last - begin);
}

void pgt_flush_range(struct user_mode_ctx *uctx, vaddr_t begin, vaddr_t last)
{
	struct pgt_cache *pgt_cache = &uctx->pgt_cache;
	struct pgt *next_p = NULL;
	struct pgt *p = NULL;

	/*
	 * Do the special case where the first element in the list is
	 * removed first.
	 */
	p = SLIST_FIRST(pgt_cache);
	while (pgt_entry_matches(p, begin, last)) {
		SLIST_REMOVE_HEAD(pgt_cache, link);
		free_pgt(p);
		p = SLIST_FIRST(pgt_cache);
	}

	/*
	 * p either points to the first element in the list or it's NULL,
	 * if NULL the list is empty and we're done.
	 */
	if (!p)
		return;

	/*
	 * Do the common case where the next element in the list is
	 * removed.
	 */
	while (true) {
		next_p = SLIST_NEXT(p, link);
		if (!next_p)
			break;
		if (pgt_entry_matches(next_p, begin, last)) {
			SLIST_REMOVE_AFTER(p, link);
			free_pgt(next_p);
			continue;
		}

		p = SLIST_NEXT(p, link);
	}
}

void pgt_flush(struct user_mode_ctx *uctx)
{
	struct pgt_cache *pgt_cache = &uctx->pgt_cache;
	struct pgt *p = NULL;

	while (true) {
		p = SLIST_FIRST(pgt_cache);
		if (!p)
			break;
		SLIST_REMOVE_HEAD(pgt_cache, link);
		free_pgt(p);
	}
}

void pgt_clear_range(struct user_mode_ctx *uctx, vaddr_t begin, vaddr_t end)
{
	struct pgt_cache *pgt_cache = &uctx->pgt_cache;
	struct pgt *p = NULL;
#ifdef CFG_WITH_LPAE
	uint64_t *tbl = NULL;
#else
	uint32_t *tbl = NULL;
#endif
	unsigned int idx = 0;
	unsigned int n = 0;

	SLIST_FOREACH(p, pgt_cache, link) {
		vaddr_t b = MAX(p->vabase, begin);
		vaddr_t e = MIN(p->vabase + CORE_MMU_PGDIR_SIZE, end);

		if (b >= e)
			continue;

		tbl = p->tbl;
		idx = (b - p->vabase) / SMALL_PAGE_SIZE;
		n = (e - b) / SMALL_PAGE_SIZE;
		memset(tbl + idx, 0, n * sizeof(*tbl));
	}
}

static struct pgt *prune_before_va(struct pgt_cache *pgt_cache, struct pgt *p,
				   struct pgt *pp, vaddr_t va)
{
	while (p && p->vabase < va) {
		if (pp) {
			assert(p == SLIST_NEXT(pp, link));
			SLIST_REMOVE_AFTER(pp, link);
			free_pgt(p);
			p = SLIST_NEXT(pp, link);
		} else {
			assert(p == SLIST_FIRST(pgt_cache));
			SLIST_REMOVE_HEAD(pgt_cache, link);
			free_pgt(p);
			p = SLIST_FIRST(pgt_cache);
		}
	}

	return p;
}

bool pgt_check_avail(struct user_mode_ctx *uctx)
{
	struct pgt_cache *pgt_cache = &uctx->pgt_cache;
	struct vm_info *vm_info = &uctx->vm_info;
	struct pgt *p = SLIST_FIRST(pgt_cache);
	struct vm_region *r = NULL;
	struct pgt *pp = NULL;
	vaddr_t va = 0;
	bool p_used = false;

	/*
	 * Prune unused tables. This is normally not needed since
	 * pgt_flush_range() does this too, but in the error path of for
	 * instance vm_remap() such calls may not be done. So for increased
	 * robustness remove all unused translation tables before we may
	 * allocate new ones.
	 */
	TAILQ_FOREACH(r, &vm_info->regions, link) {
		for (va = ROUNDDOWN(r->va, CORE_MMU_PGDIR_SIZE);
		     va < r->va + r->size; va += CORE_MMU_PGDIR_SIZE) {
			if (!p_used)
				p = prune_before_va(pgt_cache, p, pp, va);
			if (!p)
				goto prune_done;

			if (p->vabase < va) {
				pp = p;
				p = SLIST_NEXT(pp, link);
				if (!p)
					goto prune_done;
				p_used = false;
			}

			if (p->vabase == va)
				p_used = true;
		}
	}
prune_done:

	p = SLIST_FIRST(pgt_cache);
	pp = NULL;
	TAILQ_FOREACH(r, &vm_info->regions, link) {
		for (va = ROUNDDOWN(r->va, CORE_MMU_PGDIR_SIZE);
		     va < r->va + r->size; va += CORE_MMU_PGDIR_SIZE) {
			if (p && p->vabase < va) {
				pp = p;
				p = SLIST_NEXT(pp, link);
			}

			if (p) {
				if (p->vabase == va)
					continue;
				assert(p->vabase > va);
			}

			p = alloc_pgt(va);
			if (!p)
				return false;

			if (pp)
				SLIST_INSERT_AFTER(pp, p, link);
			else
				SLIST_INSERT_HEAD(pgt_cache, p, link);
		}
	}

	return true;
}
#else /* !CFG_CORE_PREALLOC_EL0_TBLS */

#if defined(CFG_WITH_PAGER) && !defined(CFG_WITH_LPAE)
static struct pgt_parent pgt_parents[PGT_CACHE_SIZE / PGT_NUM_PGT_PER_PAGE];
#else

static struct pgt_cache pgt_free_list = SLIST_HEAD_INITIALIZER(pgt_free_list);
#endif

/*
 * When a user TA context is temporarily unmapped the used struct pgt's of
 * the context (page tables holding valid physical pages) are saved in this
 * cache in the hope that it will remain in the cache when the context is
 * mapped again.
 */
static struct pgt_cache pgt_cache_list = SLIST_HEAD_INITIALIZER(pgt_cache_list);

static struct pgt pgt_entries[PGT_CACHE_SIZE];

static struct mutex pgt_mu = MUTEX_INITIALIZER;
static struct condvar pgt_cv = CONDVAR_INITIALIZER;

#if defined(CFG_WITH_PAGER) && defined(CFG_WITH_LPAE)
/*
 * Simple allocation of translation tables from pager, one translation
 * table is one page.
 */
void pgt_init(void)
{
	size_t n;

	for (n = 0; n < PGT_CACHE_SIZE; n++) {
		struct pgt *p = pgt_entries + n;

		p->tbl = tee_pager_alloc(PGT_SIZE);
		SLIST_INSERT_HEAD(&pgt_free_list, p, link);
	}
}
#elif defined(CFG_WITH_PAGER) && !defined(CFG_WITH_LPAE)
/*
 * Four translation tables per page -> need to keep track of the page
 * allocated from the pager.
 */
void pgt_init(void)
{
	size_t n;
	size_t m;

	COMPILE_TIME_ASSERT(PGT_CACHE_SIZE % PGT_NUM_PGT_PER_PAGE == 0);
	COMPILE_TIME_ASSERT(PGT_SIZE * PGT_NUM_PGT_PER_PAGE == SMALL_PAGE_SIZE);

	for (n = 0; n < ARRAY_SIZE(pgt_parents); n++) {
		uint8_t *tbl = tee_pager_alloc(SMALL_PAGE_SIZE);

		SLIST_INIT(&pgt_parents[n].pgt_cache);
		for (m = 0; m < PGT_NUM_PGT_PER_PAGE; m++) {
			struct pgt *p = pgt_entries +
					n * PGT_NUM_PGT_PER_PAGE + m;

			p->tbl = tbl + m * PGT_SIZE;
			p->parent = &pgt_parents[n];
			SLIST_INSERT_HEAD(&pgt_parents[n].pgt_cache, p, link);
		}
	}
}
#else
/* Static allocation of translation tables */
void pgt_init(void)
{
	/*
	 * We're putting this in .nozi.* instead of .bss because .nozi.* already
	 * has a large alignment, while .bss has a small alignment. The current
	 * link script is optimized for small alignment in .bss
	 */
	static uint8_t pgt_tables[PGT_CACHE_SIZE][PGT_SIZE]
			__aligned(PGT_SIZE) __section(".nozi.pgt_cache");
	size_t n;

	for (n = 0; n < ARRAY_SIZE(pgt_tables); n++) {
		struct pgt *p = pgt_entries + n;

		p->tbl = pgt_tables[n];
		SLIST_INSERT_HEAD(&pgt_free_list, p, link);
	}
}
#endif

#if defined(CFG_WITH_LPAE) || !defined(CFG_WITH_PAGER)
/* Simple allocation of translation tables from pager or static allocation */
static struct pgt *pop_from_free_list(void)
{
	struct pgt *p = SLIST_FIRST(&pgt_free_list);

	if (p) {
		SLIST_REMOVE_HEAD(&pgt_free_list, link);
		memset(p->tbl, 0, PGT_SIZE);
		p->populated = false;
	}
	return p;
}

static void push_to_free_list(struct pgt *p)
{
	SLIST_INSERT_HEAD(&pgt_free_list, p, link);
#if defined(CFG_WITH_PAGER)
	tee_pager_release_phys(p->tbl, PGT_SIZE);
#endif
}
#else
/*
 * Four translation tables per page -> need to keep track of the page
 * allocated from the pager.
 */
static struct pgt *pop_from_free_list(void)
{
	size_t n;

	for (n = 0; n < ARRAY_SIZE(pgt_parents); n++) {
		struct pgt *p = SLIST_FIRST(&pgt_parents[n].pgt_cache);

		if (p) {
			SLIST_REMOVE_HEAD(&pgt_parents[n].pgt_cache, link);
			pgt_parents[n].num_used++;
			memset(p->tbl, 0, PGT_SIZE);
			p->populated = false;
			return p;
		}
	}
	return NULL;
}

static void push_to_free_list(struct pgt *p)
{
	SLIST_INSERT_HEAD(&p->parent->pgt_cache, p, link);
	assert(p->parent->num_used > 0);
	p->parent->num_used--;
	if (!p->parent->num_used) {
		vaddr_t va = (vaddr_t)p->tbl & ~SMALL_PAGE_MASK;

		tee_pager_release_phys((void *)va, SMALL_PAGE_SIZE);
	}
}
#endif

static void push_to_cache_list(struct pgt *pgt)
{
	SLIST_INSERT_HEAD(&pgt_cache_list, pgt, link);
}

static bool match_pgt(struct pgt *pgt, vaddr_t vabase, void *ctx)
{
	return pgt->ctx == ctx && pgt->vabase == vabase;
}

static struct pgt *pop_from_cache_list(vaddr_t vabase, void *ctx)
{
	struct pgt *pgt;
	struct pgt *p;

	pgt = SLIST_FIRST(&pgt_cache_list);
	if (!pgt)
		return NULL;
	if (match_pgt(pgt, vabase, ctx)) {
		SLIST_REMOVE_HEAD(&pgt_cache_list, link);
		return pgt;
	}

	while (true) {
		p = SLIST_NEXT(pgt, link);
		if (!p)
			break;
		if (match_pgt(p, vabase, ctx)) {
			SLIST_REMOVE_AFTER(pgt, link);
			break;
		}
		pgt = p;
	}
	return p;
}

static uint16_t get_num_used_entries(struct pgt *pgt __maybe_unused)
{
#ifdef CFG_PAGED_USER_TA
	return pgt->num_used_entries;
#else
	return 0;
#endif
}

static struct pgt *pop_least_used_from_cache_list(void)
{
	struct pgt *pgt = NULL;
	struct pgt *p_prev = NULL;
	size_t least_used = 0;
	size_t next_used = 0;

	pgt = SLIST_FIRST(&pgt_cache_list);
	if (!pgt)
		return NULL;
	least_used = get_num_used_entries(pgt);

	while (true) {
		if (!SLIST_NEXT(pgt, link))
			break;
		next_used = get_num_used_entries(SLIST_NEXT(pgt, link));
		if (next_used <= least_used) {
			p_prev = pgt;
			least_used = next_used;
		}
		pgt = SLIST_NEXT(pgt, link);
	}

	if (p_prev) {
		pgt = SLIST_NEXT(p_prev, link);
		SLIST_REMOVE_AFTER(p_prev, link);
	} else {
		pgt = SLIST_FIRST(&pgt_cache_list);
		SLIST_REMOVE_HEAD(&pgt_cache_list, link);
	}
	return pgt;
}

static void pgt_free_unlocked(struct pgt_cache *pgt_cache)
{
	while (!SLIST_EMPTY(pgt_cache)) {
		struct pgt *p = SLIST_FIRST(pgt_cache);

		SLIST_REMOVE_HEAD(pgt_cache, link);

		/*
		 * With paging enabled we free all tables which doesn't
		 * refer to any paged pages any longer. This reduces the
		 * pressure the pool of physical pages.
		 */
		if (IS_ENABLED(CFG_PAGED_USER_TA) && !get_num_used_entries(p)) {
			tee_pager_pgt_save_and_release_entries(p);
			p->ctx = NULL;
			p->vabase = 0;

			push_to_free_list(p);
			continue;
		}

		push_to_cache_list(p);
	}
}

static struct pgt *pop_from_some_list(vaddr_t vabase, void *ctx)
{
	struct pgt *p = pop_from_cache_list(vabase, ctx);

	if (p)
		return p;
	p = pop_from_free_list();
	if (!p) {
		p = pop_least_used_from_cache_list();
		if (!p)
			return NULL;
		tee_pager_pgt_save_and_release_entries(p);
		memset(p->tbl, 0, PGT_SIZE);
		p->populated = false;
	}
	p->ctx = ctx;
	p->vabase = vabase;
	return p;
}

void pgt_flush(struct user_mode_ctx *uctx)
{
	struct ts_ctx *ctx = uctx->ts_ctx;
	struct pgt *pp = NULL;
	struct pgt *p = NULL;

	mutex_lock(&pgt_mu);

	while (true) {
		p = SLIST_FIRST(&pgt_cache_list);
		if (!p)
			goto out;
		if (p->ctx != ctx)
			break;
		SLIST_REMOVE_HEAD(&pgt_cache_list, link);
		tee_pager_pgt_save_and_release_entries(p);
		p->ctx = NULL;
		p->vabase = 0;
		push_to_free_list(p);
	}

	pp = p;
	while (true) {
		p = SLIST_NEXT(pp, link);
		if (!p)
			break;
		if (p->ctx == ctx) {
			SLIST_REMOVE_AFTER(pp, link);
			tee_pager_pgt_save_and_release_entries(p);
			p->ctx = NULL;
			p->vabase = 0;
			push_to_free_list(p);
		} else {
			pp = p;
		}
	}

out:
	mutex_unlock(&pgt_mu);
}

static void flush_pgt_entry(struct pgt *p)
{
	tee_pager_pgt_save_and_release_entries(p);
	p->ctx = NULL;
	p->vabase = 0;
}

static bool pgt_entry_matches(struct pgt *p, void *ctx, vaddr_t begin,
			      vaddr_t last)
{
	if (!p)
		return false;
	if (p->ctx != ctx)
		return false;
	if (last <= begin)
		return false;
	if (!core_is_buffer_inside(p->vabase, CORE_MMU_PGDIR_SIZE, begin,
				   last - begin))
		return false;

	return true;
}

static void flush_ctx_range_from_list(struct pgt_cache *pgt_cache, void *ctx,
				      vaddr_t begin, vaddr_t last)
{
	struct pgt *p;
	struct pgt *next_p;

	/*
	 * Do the special case where the first element in the list is
	 * removed first.
	 */
	p = SLIST_FIRST(pgt_cache);
	while (pgt_entry_matches(p, ctx, begin, last)) {
		flush_pgt_entry(p);
		SLIST_REMOVE_HEAD(pgt_cache, link);
		push_to_free_list(p);
		p = SLIST_FIRST(pgt_cache);
	}

	/*
	 * p either points to the first element in the list or it's NULL,
	 * if NULL the list is empty and we're done.
	 */
	if (!p)
		return;

	/*
	 * Do the common case where the next element in the list is
	 * removed.
	 */
	while (true) {
		next_p = SLIST_NEXT(p, link);
		if (!next_p)
			break;
		if (pgt_entry_matches(next_p, ctx, begin, last)) {
			flush_pgt_entry(next_p);
			SLIST_REMOVE_AFTER(p, link);
			push_to_free_list(next_p);
			continue;
		}

		p = SLIST_NEXT(p, link);
	}
}

void pgt_flush_range(struct user_mode_ctx *uctx, vaddr_t begin, vaddr_t last)
{
	struct pgt_cache *pgt_cache = &uctx->pgt_cache;
	struct ts_ctx *ctx = uctx->ts_ctx;

	mutex_lock(&pgt_mu);

	flush_ctx_range_from_list(pgt_cache, ctx, begin, last);
	flush_ctx_range_from_list(&pgt_cache_list, ctx, begin, last);

	condvar_broadcast(&pgt_cv);
	mutex_unlock(&pgt_mu);
}

static void clear_ctx_range_from_list(struct pgt_cache *pgt_cache,
				      void *ctx, vaddr_t begin, vaddr_t end)
{
	struct pgt *p = NULL;
#ifdef CFG_WITH_LPAE
	uint64_t *tbl = NULL;
#else
	uint32_t *tbl = NULL;
#endif
	unsigned int idx = 0;
	unsigned int n = 0;

	SLIST_FOREACH(p, pgt_cache, link) {
		vaddr_t b = MAX(p->vabase, begin);
		vaddr_t e = MIN(p->vabase + CORE_MMU_PGDIR_SIZE, end);

		if (p->ctx != ctx)
			continue;
		if (b >= e)
			continue;

		tbl = p->tbl;
		idx = (b - p->vabase) / SMALL_PAGE_SIZE;
		n = (e - b) / SMALL_PAGE_SIZE;
		memset(tbl + idx, 0, n * sizeof(*tbl));
	}
}

void pgt_clear_range(struct user_mode_ctx *uctx, vaddr_t begin, vaddr_t end)
{
	struct pgt_cache *pgt_cache = &uctx->pgt_cache;
	struct ts_ctx *ctx = uctx->ts_ctx;

	mutex_lock(&pgt_mu);

	clear_ctx_range_from_list(pgt_cache, ctx, begin, end);
	clear_ctx_range_from_list(&pgt_cache_list, ctx, begin, end);

	mutex_unlock(&pgt_mu);
}

static bool pgt_alloc_unlocked(struct pgt_cache *pgt_cache, struct ts_ctx *ctx,
			       struct vm_info *vm_info)
{
	struct vm_region *r = NULL;
	struct pgt *pp = NULL;
	struct pgt *p = NULL;
	vaddr_t va = 0;

	TAILQ_FOREACH(r, &vm_info->regions, link) {
		for (va = ROUNDDOWN(r->va, CORE_MMU_PGDIR_SIZE);
		     va < r->va + r->size; va += CORE_MMU_PGDIR_SIZE) {
			if (p && p->vabase == va)
				continue;
			p = pop_from_some_list(va, ctx);
			if (!p) {
				pgt_free_unlocked(pgt_cache);
				return false;
			}
			if (pp)
				SLIST_INSERT_AFTER(pp, p, link);
			else
				SLIST_INSERT_HEAD(pgt_cache, p, link);
			pp = p;
		}
	}

	return true;
}

bool pgt_check_avail(struct user_mode_ctx *uctx)
{
	struct vm_info *vm_info = &uctx->vm_info;
	struct vm_region *r = NULL;
	size_t tbl_count = 0;
	vaddr_t last_va = 0;
	vaddr_t va = 0;

	TAILQ_FOREACH(r, &vm_info->regions, link) {
		for (va = ROUNDDOWN(r->va, CORE_MMU_PGDIR_SIZE);
		     va < r->va + r->size; va += CORE_MMU_PGDIR_SIZE) {
			if (va == last_va)
				continue;
			tbl_count++;
			last_va = va;
		}
	}

	return tbl_count <= PGT_CACHE_SIZE;
}

void pgt_get_all(struct user_mode_ctx *uctx)
{
	struct pgt_cache *pgt_cache = &uctx->pgt_cache;
	struct vm_info *vm_info = &uctx->vm_info;

	if (TAILQ_EMPTY(&vm_info->regions))
		return;

	mutex_lock(&pgt_mu);

	pgt_free_unlocked(pgt_cache);
	while (!pgt_alloc_unlocked(pgt_cache, uctx->ts_ctx, vm_info)) {
		assert(pgt_check_avail(uctx));
		DMSG("Waiting for page tables");
		condvar_broadcast(&pgt_cv);
		condvar_wait(&pgt_cv, &pgt_mu);
	}

	mutex_unlock(&pgt_mu);
}

void pgt_put_all(struct user_mode_ctx *uctx)
{
	struct pgt_cache *pgt_cache = &uctx->pgt_cache;

	if (SLIST_EMPTY(pgt_cache))
		return;

	mutex_lock(&pgt_mu);

	pgt_free_unlocked(pgt_cache);

	condvar_broadcast(&pgt_cv);
	mutex_unlock(&pgt_mu);
}

struct pgt *pgt_pop_from_cache_list(vaddr_t vabase, struct ts_ctx *ctx)
{
	struct pgt *pgt = NULL;

	mutex_lock(&pgt_mu);
	pgt = pop_from_cache_list(vabase, ctx);
	mutex_unlock(&pgt_mu);

	return pgt;
}

void pgt_push_to_cache_list(struct pgt *pgt)
{
	mutex_lock(&pgt_mu);
	push_to_cache_list(pgt);
	mutex_unlock(&pgt_mu);
}

#endif /* !CFG_CORE_PREALLOC_EL0_TBLS */