// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *  IOMMU helpers in MMU context.
 *
 *  Copyright (C) 2015 IBM Corp. <aik@ozlabs.ru>
 */

#include <linux/sched/signal.h>
#include <linux/slab.h>
#include <linux/rculist.h>
#include <linux/vmalloc.h>
#include <linux/mutex.h>
#include <linux/migrate.h>
#include <linux/hugetlb.h>
#include <linux/swap.h>
#include <linux/sizes.h>
#include <linux/mm.h>
#include <asm/mmu_context.h>
#include <asm/pte-walk.h>
#include <linux/mm_inline.h>

static DEFINE_MUTEX(mem_list_mutex);

#define MM_IOMMU_TABLE_GROUP_PAGE_DIRTY 0x1
#define MM_IOMMU_TABLE_GROUP_PAGE_MASK  ~(SZ_4K - 1)

struct mm_iommu_table_group_mem_t {
        struct list_head next;
        struct rcu_head rcu;
        unsigned long used;
        atomic64_t mapped;
        unsigned int pageshift;
        u64 ua;                 /* userspace address */
        u64 entries;            /* number of entries in hpas/hpages[] */
        /*
         * in mm_iommu_get we temporarily use this to store
         * struct page address.
         *
         * We need to convert ua to hpa in real mode. Make it
         * simpler by storing physical address.
         */
        union {
                struct page **hpages;   /* vmalloc'ed */
                phys_addr_t *hpas;
        };
#define MM_IOMMU_TABLE_INVALID_HPA      ((uint64_t)-1)
        u64 dev_hpa;            /* Device memory base address */
};

bool mm_iommu_preregistered(struct mm_struct *mm)
{
        return !list_empty(&mm->context.iommu_group_mem_list);
}
EXPORT_SYMBOL_GPL(mm_iommu_preregistered);

static long mm_iommu_do_alloc(struct mm_struct *mm, unsigned long ua,
                              unsigned long entries, unsigned long dev_hpa,
                              struct mm_iommu_table_group_mem_t **pmem)
{
        struct mm_iommu_table_group_mem_t *mem, *mem2;
        long i, ret, locked_entries = 0, pinned = 0;
        unsigned int pageshift;
        unsigned long entry, chunk;

        if (dev_hpa == MM_IOMMU_TABLE_INVALID_HPA) {
                ret = account_locked_vm(mm, entries, true);
                if (ret)
                        return ret;

                locked_entries = entries;
        }

        mem = kzalloc_obj(*mem);
        if (!mem) {
                ret = -ENOMEM;
                goto unlock_exit;
        }

        if (dev_hpa != MM_IOMMU_TABLE_INVALID_HPA) {
                mem->pageshift = __ffs(dev_hpa | (entries << PAGE_SHIFT));
                mem->dev_hpa = dev_hpa;
                goto good_exit;
        }
        mem->dev_hpa = MM_IOMMU_TABLE_INVALID_HPA;

        /*
         * For a starting point for a maximum page size calculation
         * we use @ua and @entries natural alignment to allow IOMMU pages
         * smaller than huge pages but still bigger than PAGE_SIZE.
         */
        mem->pageshift = __ffs(ua | (entries << PAGE_SHIFT));
        mem->hpas = vzalloc(array_size(entries, sizeof(mem->hpas[0])));
        if (!mem->hpas) {
                kfree(mem);
                ret = -ENOMEM;
                goto unlock_exit;
        }

        mmap_read_lock(mm);
        chunk = (1UL << (PAGE_SHIFT + MAX_PAGE_ORDER)) /
                        sizeof(struct vm_area_struct *);
        chunk = min(chunk, entries);
        for (entry = 0; entry < entries; entry += chunk) {
                unsigned long n = min(entries - entry, chunk);

                ret = pin_user_pages(ua + (entry << PAGE_SHIFT), n,
                                FOLL_WRITE | FOLL_LONGTERM,
                                mem->hpages + entry);
                if (ret == n) {
                        pinned += n;
                        continue;
                }
                if (ret > 0)
                        pinned += ret;
                break;
        }
        mmap_read_unlock(mm);
        if (pinned != entries) {
                if (!ret)
                        ret = -EFAULT;
                goto free_exit;
        }

good_exit:
        atomic64_set(&mem->mapped, 1);
        mem->used = 1;
        mem->ua = ua;
        mem->entries = entries;

        mutex_lock(&mem_list_mutex);

        list_for_each_entry_rcu(mem2, &mm->context.iommu_group_mem_list, next,
                                lockdep_is_held(&mem_list_mutex)) {
                /* Overlap? */
                if ((mem2->ua < (ua + (entries << PAGE_SHIFT))) &&
                                (ua < (mem2->ua +
                                       (mem2->entries << PAGE_SHIFT)))) {
                        ret = -EINVAL;
                        mutex_unlock(&mem_list_mutex);
                        goto free_exit;
                }
        }

        if (mem->dev_hpa == MM_IOMMU_TABLE_INVALID_HPA) {
                /*
                 * Allow to use larger than 64k IOMMU pages. Only do that
                 * if we are backed by hugetlb. Skip device memory as it is not
                 * backed with page structs.
                 */
                pageshift = PAGE_SHIFT;
                for (i = 0; i < entries; ++i) {
                        struct page *page = mem->hpages[i];

                        if ((mem->pageshift > PAGE_SHIFT) && PageHuge(page))
                                pageshift = page_shift(compound_head(page));
                        mem->pageshift = min(mem->pageshift, pageshift);
                        /*
                         * We don't need struct page reference any more, switch
                         * to physical address.
                         */
                        mem->hpas[i] = page_to_pfn(page) << PAGE_SHIFT;
                }
        }

        list_add_rcu(&mem->next, &mm->context.iommu_group_mem_list);

        mutex_unlock(&mem_list_mutex);

        *pmem = mem;

        return 0;

free_exit:
        /* free the references taken */
        unpin_user_pages(mem->hpages, pinned);

        vfree(mem->hpas);
        kfree(mem);

unlock_exit:
        account_locked_vm(mm, locked_entries, false);

        return ret;
}

long mm_iommu_new(struct mm_struct *mm, unsigned long ua, unsigned long entries,
                struct mm_iommu_table_group_mem_t **pmem)
{
        return mm_iommu_do_alloc(mm, ua, entries, MM_IOMMU_TABLE_INVALID_HPA,
                        pmem);
}
EXPORT_SYMBOL_GPL(mm_iommu_new);

long mm_iommu_newdev(struct mm_struct *mm, unsigned long ua,
                unsigned long entries, unsigned long dev_hpa,
                struct mm_iommu_table_group_mem_t **pmem)
{
        return mm_iommu_do_alloc(mm, ua, entries, dev_hpa, pmem);
}
EXPORT_SYMBOL_GPL(mm_iommu_newdev);

static void mm_iommu_unpin(struct mm_iommu_table_group_mem_t *mem)
{
        long i;
        struct page *page = NULL;

        if (!mem->hpas)
                return;

        for (i = 0; i < mem->entries; ++i) {
                if (!mem->hpas[i])
                        continue;

                page = pfn_to_page(mem->hpas[i] >> PAGE_SHIFT);
                if (!page)
                        continue;

                if (mem->hpas[i] & MM_IOMMU_TABLE_GROUP_PAGE_DIRTY)
                        SetPageDirty(page);

                unpin_user_page(page);

                mem->hpas[i] = 0;
        }
}

static void mm_iommu_do_free(struct mm_iommu_table_group_mem_t *mem)
{

        mm_iommu_unpin(mem);
        vfree(mem->hpas);
        kfree(mem);
}

static void mm_iommu_free(struct rcu_head *head)
{
        struct mm_iommu_table_group_mem_t *mem = container_of(head,
                        struct mm_iommu_table_group_mem_t, rcu);

        mm_iommu_do_free(mem);
}

static void mm_iommu_release(struct mm_iommu_table_group_mem_t *mem)
{
        list_del_rcu(&mem->next);
        call_rcu(&mem->rcu, mm_iommu_free);
}

long mm_iommu_put(struct mm_struct *mm, struct mm_iommu_table_group_mem_t *mem)
{
        long ret = 0;
        unsigned long unlock_entries = 0;

        mutex_lock(&mem_list_mutex);

        if (mem->used == 0) {
                ret = -ENOENT;
                goto unlock_exit;
        }

        --mem->used;
        /* There are still users, exit */
        if (mem->used)
                goto unlock_exit;

        /* Are there still mappings? */
        if (atomic64_cmpxchg(&mem->mapped, 1, 0) != 1) {
                ++mem->used;
                ret = -EBUSY;
                goto unlock_exit;
        }

        if (mem->dev_hpa == MM_IOMMU_TABLE_INVALID_HPA)
                unlock_entries = mem->entries;

        /* @mapped became 0 so now mappings are disabled, release the region */
        mm_iommu_release(mem);

unlock_exit:
        mutex_unlock(&mem_list_mutex);

        account_locked_vm(mm, unlock_entries, false);

        return ret;
}
EXPORT_SYMBOL_GPL(mm_iommu_put);

struct mm_iommu_table_group_mem_t *mm_iommu_lookup(struct mm_struct *mm,
                unsigned long ua, unsigned long size)
{
        struct mm_iommu_table_group_mem_t *mem, *ret = NULL;

        rcu_read_lock();
        list_for_each_entry_rcu(mem, &mm->context.iommu_group_mem_list, next) {
                if ((mem->ua <= ua) &&
                                (ua + size <= mem->ua +
                                 (mem->entries << PAGE_SHIFT))) {
                        ret = mem;
                        break;
                }
        }
        rcu_read_unlock();

        return ret;
}
EXPORT_SYMBOL_GPL(mm_iommu_lookup);

struct mm_iommu_table_group_mem_t *mm_iommu_get(struct mm_struct *mm,
                unsigned long ua, unsigned long entries)
{
        struct mm_iommu_table_group_mem_t *mem, *ret = NULL;

        mutex_lock(&mem_list_mutex);

        list_for_each_entry_rcu(mem, &mm->context.iommu_group_mem_list, next,
                                lockdep_is_held(&mem_list_mutex)) {
                if ((mem->ua == ua) && (mem->entries == entries)) {
                        ret = mem;
                        ++mem->used;
                        break;
                }
        }

        mutex_unlock(&mem_list_mutex);

        return ret;
}
EXPORT_SYMBOL_GPL(mm_iommu_get);

long mm_iommu_ua_to_hpa(struct mm_iommu_table_group_mem_t *mem,
                unsigned long ua, unsigned int pageshift, unsigned long *hpa)
{
        const long entry = (ua - mem->ua) >> PAGE_SHIFT;
        u64 *va;

        if (entry >= mem->entries)
                return -EFAULT;

        if (pageshift > mem->pageshift)
                return -EFAULT;

        if (!mem->hpas) {
                *hpa = mem->dev_hpa + (ua - mem->ua);
                return 0;
        }

        va = &mem->hpas[entry];
        *hpa = (*va & MM_IOMMU_TABLE_GROUP_PAGE_MASK) | (ua & ~PAGE_MASK);

        return 0;
}
EXPORT_SYMBOL_GPL(mm_iommu_ua_to_hpa);

bool mm_iommu_is_devmem(struct mm_struct *mm, unsigned long hpa,
                unsigned int pageshift, unsigned long *size)
{
        struct mm_iommu_table_group_mem_t *mem;
        unsigned long end;

        rcu_read_lock();
        list_for_each_entry_rcu(mem, &mm->context.iommu_group_mem_list, next) {
                if (mem->dev_hpa == MM_IOMMU_TABLE_INVALID_HPA)
                        continue;

                end = mem->dev_hpa + (mem->entries << PAGE_SHIFT);
                if ((mem->dev_hpa <= hpa) && (hpa < end)) {
                        /*
                         * Since the IOMMU page size might be bigger than
                         * PAGE_SIZE, the amount of preregistered memory
                         * starting from @hpa might be smaller than 1<<pageshift
                         * and the caller needs to distinguish this situation.
                         */
                        *size = min(1UL << pageshift, end - hpa);
                        return true;
                }
        }
        rcu_read_unlock();

        return false;
}
EXPORT_SYMBOL_GPL(mm_iommu_is_devmem);

long mm_iommu_mapped_inc(struct mm_iommu_table_group_mem_t *mem)
{
        if (atomic64_inc_not_zero(&mem->mapped))
                return 0;

        /* Last mm_iommu_put() has been called, no more mappings allowed() */
        return -ENXIO;
}
EXPORT_SYMBOL_GPL(mm_iommu_mapped_inc);

void mm_iommu_mapped_dec(struct mm_iommu_table_group_mem_t *mem)
{
        atomic64_add_unless(&mem->mapped, -1, 1);
}
EXPORT_SYMBOL_GPL(mm_iommu_mapped_dec);

void mm_iommu_init(struct mm_struct *mm)
{
        INIT_LIST_HEAD_RCU(&mm->context.iommu_group_mem_list);
}