// SPDX-License-Identifier: GPL-2.0
/*
 *  Page table allocation functions
 *
 *    Copyright IBM Corp. 2016
 *    Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
 */

#include <linux/sysctl.h>
#include <linux/slab.h>
#include <linux/mm.h>
#include <asm/mmu_context.h>
#include <asm/pgalloc.h>
#include <asm/gmap.h>
#include <asm/tlb.h>
#include <asm/tlbflush.h>

#ifdef CONFIG_PGSTE

static int page_table_allocate_pgste_min = 0;
static int page_table_allocate_pgste_max = 1;
int page_table_allocate_pgste = 0;
EXPORT_SYMBOL(page_table_allocate_pgste);

static struct ctl_table page_table_sysctl[] = {
        {
                .procname       = "allocate_pgste",
                .data           = &page_table_allocate_pgste,
                .maxlen         = sizeof(int),
                .mode           = S_IRUGO | S_IWUSR,
                .proc_handler   = proc_dointvec,
                .extra1         = &page_table_allocate_pgste_min,
                .extra2         = &page_table_allocate_pgste_max,
        },
        { }
};

static struct ctl_table page_table_sysctl_dir[] = {
        {
                .procname       = "vm",
                .maxlen         = 0,
                .mode           = 0555,
                .child          = page_table_sysctl,
        },
        { }
};

static int __init page_table_register_sysctl(void)
{
        return register_sysctl_table(page_table_sysctl_dir) ? 0 : -ENOMEM;
}
__initcall(page_table_register_sysctl);

#endif /* CONFIG_PGSTE */

unsigned long *crst_table_alloc(struct mm_struct *mm)
{
        struct page *page = alloc_pages(GFP_KERNEL, 2);

        if (!page)
                return NULL;
        arch_set_page_dat(page, 2);
        return (unsigned long *) page_to_phys(page);
}

void crst_table_free(struct mm_struct *mm, unsigned long *table)
{
        free_pages((unsigned long) table, 2);
}

static void __crst_table_upgrade(void *arg)
{
        struct mm_struct *mm = arg;

        if (current->active_mm == mm)
                set_user_asce(mm);
        __tlb_flush_local();
}

int crst_table_upgrade(struct mm_struct *mm, unsigned long end)
{
        unsigned long *table, *pgd;
        int rc, notify;

        /* upgrade should only happen from 3 to 4, 3 to 5, or 4 to 5 levels */
        VM_BUG_ON(mm->context.asce_limit < _REGION2_SIZE);
        rc = 0;
        notify = 0;
        while (mm->context.asce_limit < end) {
                table = crst_table_alloc(mm);
                if (!table) {
                        rc = -ENOMEM;
                        break;
                }
                spin_lock_bh(&mm->page_table_lock);
                pgd = (unsigned long *) mm->pgd;
                if (mm->context.asce_limit == _REGION2_SIZE) {
                        crst_table_init(table, _REGION2_ENTRY_EMPTY);
                        p4d_populate(mm, (p4d_t *) table, (pud_t *) pgd);
                        mm->pgd = (pgd_t *) table;
                        mm->context.asce_limit = _REGION1_SIZE;
                        mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH |
                                _ASCE_USER_BITS | _ASCE_TYPE_REGION2;
                } else {
                        crst_table_init(table, _REGION1_ENTRY_EMPTY);
                        pgd_populate(mm, (pgd_t *) table, (p4d_t *) pgd);
                        mm->pgd = (pgd_t *) table;
                        mm->context.asce_limit = -PAGE_SIZE;
                        mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH |
                                _ASCE_USER_BITS | _ASCE_TYPE_REGION1;
                }
                notify = 1;
                spin_unlock_bh(&mm->page_table_lock);
        }
        if (notify)
                on_each_cpu(__crst_table_upgrade, mm, 0);
        return rc;
}

void crst_table_downgrade(struct mm_struct *mm)
{
        pgd_t *pgd;

        /* downgrade should only happen from 3 to 2 levels (compat only) */
        VM_BUG_ON(mm->context.asce_limit != _REGION2_SIZE);

        if (current->active_mm == mm) {
                clear_user_asce();
                __tlb_flush_mm(mm);
        }

        pgd = mm->pgd;
        mm->pgd = (pgd_t *) (pgd_val(*pgd) & _REGION_ENTRY_ORIGIN);
        mm->context.asce_limit = _REGION3_SIZE;
        mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH |
                           _ASCE_USER_BITS | _ASCE_TYPE_SEGMENT;
        crst_table_free(mm, (unsigned long *) pgd);

        if (current->active_mm == mm)
                set_user_asce(mm);
}

static inline unsigned int atomic_xor_bits(atomic_t *v, unsigned int bits)
{
        unsigned int old, new;

        do {
                old = atomic_read(v);
                new = old ^ bits;
        } while (atomic_cmpxchg(v, old, new) != old);
        return new;
}

#ifdef CONFIG_PGSTE

struct page *page_table_alloc_pgste(struct mm_struct *mm)
{
        struct page *page;
        u64 *table;

        page = alloc_page(GFP_KERNEL);
        if (page) {
                table = (u64 *)page_to_phys(page);
                memset64(table, _PAGE_INVALID, PTRS_PER_PTE);
                memset64(table + PTRS_PER_PTE, 0, PTRS_PER_PTE);
        }
        return page;
}

void page_table_free_pgste(struct page *page)
{
        __free_page(page);
}

#endif /* CONFIG_PGSTE */

/*
 * page table entry allocation/free routines.
 */
unsigned long *page_table_alloc(struct mm_struct *mm)
{
        unsigned long *table;
        struct page *page;
        unsigned int mask, bit;

        /* Try to get a fragment of a 4K page as a 2K page table */
        if (!mm_alloc_pgste(mm)) {
                table = NULL;
                spin_lock_bh(&mm->context.lock);
                if (!list_empty(&mm->context.pgtable_list)) {
                        page = list_first_entry(&mm->context.pgtable_list,
                                                struct page, lru);
                        mask = atomic_read(&page->_refcount) >> 24;
                        mask = (mask | (mask >> 4)) & 3;
                        if (mask != 3) {
                                table = (unsigned long *) page_to_phys(page);
                                bit = mask & 1;         /* =1 -> second 2K */
                                if (bit)
                                        table += PTRS_PER_PTE;
                                atomic_xor_bits(&page->_refcount,
                                                        1U << (bit + 24));
                                list_del(&page->lru);
                        }
                }
                spin_unlock_bh(&mm->context.lock);
                if (table)
                        return table;
        }
        /* Allocate a fresh page */
        page = alloc_page(GFP_KERNEL);
        if (!page)
                return NULL;
        if (!pgtable_page_ctor(page)) {
                __free_page(page);
                return NULL;
        }
        arch_set_page_dat(page, 0);
        /* Initialize page table */
        table = (unsigned long *) page_to_phys(page);
        if (mm_alloc_pgste(mm)) {
                /* Return 4K page table with PGSTEs */
                atomic_xor_bits(&page->_refcount, 3 << 24);
                memset64((u64 *)table, _PAGE_INVALID, PTRS_PER_PTE);
                memset64((u64 *)table + PTRS_PER_PTE, 0, PTRS_PER_PTE);
        } else {
                /* Return the first 2K fragment of the page */
                atomic_xor_bits(&page->_refcount, 1 << 24);
                memset64((u64 *)table, _PAGE_INVALID, 2 * PTRS_PER_PTE);
                spin_lock_bh(&mm->context.lock);
                list_add(&page->lru, &mm->context.pgtable_list);
                spin_unlock_bh(&mm->context.lock);
        }
        return table;
}

void page_table_free(struct mm_struct *mm, unsigned long *table)
{
        struct page *page;
        unsigned int bit, mask;

        page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
        if (!mm_alloc_pgste(mm)) {
                /* Free 2K page table fragment of a 4K page */
                bit = (__pa(table) & ~PAGE_MASK)/(PTRS_PER_PTE*sizeof(pte_t));
                spin_lock_bh(&mm->context.lock);
                mask = atomic_xor_bits(&page->_refcount, 1U << (bit + 24));
                mask >>= 24;
                if (mask & 3)
                        list_add(&page->lru, &mm->context.pgtable_list);
                else
                        list_del(&page->lru);
                spin_unlock_bh(&mm->context.lock);
                if (mask != 0)
                        return;
        } else {
                atomic_xor_bits(&page->_refcount, 3U << 24);
        }

        pgtable_page_dtor(page);
        __free_page(page);
}

void page_table_free_rcu(struct mmu_gather *tlb, unsigned long *table,
                         unsigned long vmaddr)
{
        struct mm_struct *mm;
        struct page *page;
        unsigned int bit, mask;

        mm = tlb->mm;
        page = pfn_to_page(__pa(table) >> PAGE_SHIFT);
        if (mm_alloc_pgste(mm)) {
                gmap_unlink(mm, table, vmaddr);
                table = (unsigned long *) (__pa(table) | 3);
                tlb_remove_table(tlb, table);
                return;
        }
        bit = (__pa(table) & ~PAGE_MASK) / (PTRS_PER_PTE*sizeof(pte_t));
        spin_lock_bh(&mm->context.lock);
        mask = atomic_xor_bits(&page->_refcount, 0x11U << (bit + 24));
        mask >>= 24;
        if (mask & 3)
                list_add_tail(&page->lru, &mm->context.pgtable_list);
        else
                list_del(&page->lru);
        spin_unlock_bh(&mm->context.lock);
        table = (unsigned long *) (__pa(table) | (1U << bit));
        tlb_remove_table(tlb, table);
}

static void __tlb_remove_table(void *_table)
{
        unsigned int mask = (unsigned long) _table & 3;
        void *table = (void *)((unsigned long) _table ^ mask);
        struct page *page = pfn_to_page(__pa(table) >> PAGE_SHIFT);

        switch (mask) {
        case 0:         /* pmd, pud, or p4d */
                free_pages((unsigned long) table, 2);
                break;
        case 1:         /* lower 2K of a 4K page table */
        case 2:         /* higher 2K of a 4K page table */
                mask = atomic_xor_bits(&page->_refcount, mask << (4 + 24));
                mask >>= 24;
                if (mask != 0)
                        break;
                /* fallthrough */
        case 3:         /* 4K page table with pgstes */
                if (mask & 3)
                        atomic_xor_bits(&page->_refcount, 3 << 24);
                pgtable_page_dtor(page);
                __free_page(page);
                break;
        }
}

static void tlb_remove_table_smp_sync(void *arg)
{
        /* Simply deliver the interrupt */
}

static void tlb_remove_table_one(void *table)
{
        /*
         * This isn't an RCU grace period and hence the page-tables cannot be
         * assumed to be actually RCU-freed.
         *
         * It is however sufficient for software page-table walkers that rely
         * on IRQ disabling. See the comment near struct mmu_table_batch.
         */
        smp_call_function(tlb_remove_table_smp_sync, NULL, 1);
        __tlb_remove_table(table);
}

static void tlb_remove_table_rcu(struct rcu_head *head)
{
        struct mmu_table_batch *batch;
        int i;

        batch = container_of(head, struct mmu_table_batch, rcu);

        for (i = 0; i < batch->nr; i++)
                __tlb_remove_table(batch->tables[i]);

        free_page((unsigned long)batch);
}

void tlb_table_flush(struct mmu_gather *tlb)
{
        struct mmu_table_batch **batch = &tlb->batch;

        if (*batch) {
                call_rcu_sched(&(*batch)->rcu, tlb_remove_table_rcu);
                *batch = NULL;
        }
}

void tlb_remove_table(struct mmu_gather *tlb, void *table)
{
        struct mmu_table_batch **batch = &tlb->batch;

        tlb->mm->context.flush_mm = 1;
        if (*batch == NULL) {
                *batch = (struct mmu_table_batch *)
                        __get_free_page(GFP_NOWAIT | __GFP_NOWARN);
                if (*batch == NULL) {
                        __tlb_flush_mm_lazy(tlb->mm);
                        tlb_remove_table_one(table);
                        return;
                }
                (*batch)->nr = 0;
        }
        (*batch)->tables[(*batch)->nr++] = table;
        if ((*batch)->nr == MAX_TABLE_BATCH)
                tlb_flush_mmu(tlb);
}

/*
 * Base infrastructure required to generate basic asces, region, segment,
 * and page tables that do not make use of enhanced features like EDAT1.
 */

static struct kmem_cache *base_pgt_cache;

static unsigned long base_pgt_alloc(void)
{
        u64 *table;

        table = kmem_cache_alloc(base_pgt_cache, GFP_KERNEL);
        if (table)
                memset64(table, _PAGE_INVALID, PTRS_PER_PTE);
        return (unsigned long) table;
}

static void base_pgt_free(unsigned long table)
{
        kmem_cache_free(base_pgt_cache, (void *) table);
}

static unsigned long base_crst_alloc(unsigned long val)
{
        unsigned long table;

        table =  __get_free_pages(GFP_KERNEL, CRST_ALLOC_ORDER);
        if (table)
                crst_table_init((unsigned long *)table, val);
        return table;
}

static void base_crst_free(unsigned long table)
{
        free_pages(table, CRST_ALLOC_ORDER);
}

#define BASE_ADDR_END_FUNC(NAME, SIZE)                                  \
static inline unsigned long base_##NAME##_addr_end(unsigned long addr,  \
                                                   unsigned long end)   \
{                                                                       \
        unsigned long next = (addr + (SIZE)) & ~((SIZE) - 1);           \
                                                                        \
        return (next - 1) < (end - 1) ? next : end;                     \
}

BASE_ADDR_END_FUNC(page,    _PAGE_SIZE)
BASE_ADDR_END_FUNC(segment, _SEGMENT_SIZE)
BASE_ADDR_END_FUNC(region3, _REGION3_SIZE)
BASE_ADDR_END_FUNC(region2, _REGION2_SIZE)
BASE_ADDR_END_FUNC(region1, _REGION1_SIZE)

static inline unsigned long base_lra(unsigned long address)
{
        unsigned long real;

        asm volatile(
                "       lra     %0,0(%1)\n"
                : "=d" (real) : "a" (address) : "cc");
        return real;
}

static int base_page_walk(unsigned long origin, unsigned long addr,
                          unsigned long end, int alloc)
{
        unsigned long *pte, next;

        if (!alloc)
                return 0;
        pte = (unsigned long *) origin;
        pte += (addr & _PAGE_INDEX) >> _PAGE_SHIFT;
        do {
                next = base_page_addr_end(addr, end);
                *pte = base_lra(addr);
        } while (pte++, addr = next, addr < end);
        return 0;
}

static int base_segment_walk(unsigned long origin, unsigned long addr,
                             unsigned long end, int alloc)
{
        unsigned long *ste, next, table;
        int rc;

        ste = (unsigned long *) origin;
        ste += (addr & _SEGMENT_INDEX) >> _SEGMENT_SHIFT;
        do {
                next = base_segment_addr_end(addr, end);
                if (*ste & _SEGMENT_ENTRY_INVALID) {
                        if (!alloc)
                                continue;
                        table = base_pgt_alloc();
                        if (!table)
                                return -ENOMEM;
                        *ste = table | _SEGMENT_ENTRY;
                }
                table = *ste & _SEGMENT_ENTRY_ORIGIN;
                rc = base_page_walk(table, addr, next, alloc);
                if (rc)
                        return rc;
                if (!alloc)
                        base_pgt_free(table);
                cond_resched();
        } while (ste++, addr = next, addr < end);
        return 0;
}

static int base_region3_walk(unsigned long origin, unsigned long addr,
                             unsigned long end, int alloc)
{
        unsigned long *rtte, next, table;
        int rc;

        rtte = (unsigned long *) origin;
        rtte += (addr & _REGION3_INDEX) >> _REGION3_SHIFT;
        do {
                next = base_region3_addr_end(addr, end);
                if (*rtte & _REGION_ENTRY_INVALID) {
                        if (!alloc)
                                continue;
                        table = base_crst_alloc(_SEGMENT_ENTRY_EMPTY);
                        if (!table)
                                return -ENOMEM;
                        *rtte = table | _REGION3_ENTRY;
                }
                table = *rtte & _REGION_ENTRY_ORIGIN;
                rc = base_segment_walk(table, addr, next, alloc);
                if (rc)
                        return rc;
                if (!alloc)
                        base_crst_free(table);
        } while (rtte++, addr = next, addr < end);
        return 0;
}

static int base_region2_walk(unsigned long origin, unsigned long addr,
                             unsigned long end, int alloc)
{
        unsigned long *rste, next, table;
        int rc;

        rste = (unsigned long *) origin;
        rste += (addr & _REGION2_INDEX) >> _REGION2_SHIFT;
        do {
                next = base_region2_addr_end(addr, end);
                if (*rste & _REGION_ENTRY_INVALID) {
                        if (!alloc)
                                continue;
                        table = base_crst_alloc(_REGION3_ENTRY_EMPTY);
                        if (!table)
                                return -ENOMEM;
                        *rste = table | _REGION2_ENTRY;
                }
                table = *rste & _REGION_ENTRY_ORIGIN;
                rc = base_region3_walk(table, addr, next, alloc);
                if (rc)
                        return rc;
                if (!alloc)
                        base_crst_free(table);
        } while (rste++, addr = next, addr < end);
        return 0;
}

static int base_region1_walk(unsigned long origin, unsigned long addr,
                             unsigned long end, int alloc)
{
        unsigned long *rfte, next, table;
        int rc;

        rfte = (unsigned long *) origin;
        rfte += (addr & _REGION1_INDEX) >> _REGION1_SHIFT;
        do {
                next = base_region1_addr_end(addr, end);
                if (*rfte & _REGION_ENTRY_INVALID) {
                        if (!alloc)
                                continue;
                        table = base_crst_alloc(_REGION2_ENTRY_EMPTY);
                        if (!table)
                                return -ENOMEM;
                        *rfte = table | _REGION1_ENTRY;
                }
                table = *rfte & _REGION_ENTRY_ORIGIN;
                rc = base_region2_walk(table, addr, next, alloc);
                if (rc)
                        return rc;
                if (!alloc)
                        base_crst_free(table);
        } while (rfte++, addr = next, addr < end);
        return 0;
}

/**
 * base_asce_free - free asce and tables returned from base_asce_alloc()
 * @asce: asce to be freed
 *
 * Frees all region, segment, and page tables that were allocated with a
 * corresponding base_asce_alloc() call.
 */
void base_asce_free(unsigned long asce)
{
        unsigned long table = asce & _ASCE_ORIGIN;

        if (!asce)
                return;
        switch (asce & _ASCE_TYPE_MASK) {
        case _ASCE_TYPE_SEGMENT:
                base_segment_walk(table, 0, _REGION3_SIZE, 0);
                break;
        case _ASCE_TYPE_REGION3:
                base_region3_walk(table, 0, _REGION2_SIZE, 0);
                break;
        case _ASCE_TYPE_REGION2:
                base_region2_walk(table, 0, _REGION1_SIZE, 0);
                break;
        case _ASCE_TYPE_REGION1:
                base_region1_walk(table, 0, -_PAGE_SIZE, 0);
                break;
        }
        base_crst_free(table);
}

static int base_pgt_cache_init(void)
{
        static DEFINE_MUTEX(base_pgt_cache_mutex);
        unsigned long sz = _PAGE_TABLE_SIZE;

        if (base_pgt_cache)
                return 0;
        mutex_lock(&base_pgt_cache_mutex);
        if (!base_pgt_cache)
                base_pgt_cache = kmem_cache_create("base_pgt", sz, sz, 0, NULL);
        mutex_unlock(&base_pgt_cache_mutex);
        return base_pgt_cache ? 0 : -ENOMEM;
}

/**
 * base_asce_alloc - create kernel mapping without enhanced DAT features
 * @addr: virtual start address of kernel mapping
 * @num_pages: number of consecutive pages
 *
 * Generate an asce, including all required region, segment and page tables,
 * that can be used to access the virtual kernel mapping. The difference is
 * that the returned asce does not make use of any enhanced DAT features like
 * e.g. large pages. This is required for some I/O functions that pass an
 * asce, like e.g. some service call requests.
 *
 * Note: the returned asce may NEVER be attached to any cpu. It may only be
 *       used for I/O requests. tlb entries that might result because the
 *       asce was attached to a cpu won't be cleared.
 */
unsigned long base_asce_alloc(unsigned long addr, unsigned long num_pages)
{
        unsigned long asce, table, end;
        int rc;

        if (base_pgt_cache_init())
                return 0;
        end = addr + num_pages * PAGE_SIZE;
        if (end <= _REGION3_SIZE) {
                table = base_crst_alloc(_SEGMENT_ENTRY_EMPTY);
                if (!table)
                        return 0;
                rc = base_segment_walk(table, addr, end, 1);
                asce = table | _ASCE_TYPE_SEGMENT | _ASCE_TABLE_LENGTH;
        } else if (end <= _REGION2_SIZE) {
                table = base_crst_alloc(_REGION3_ENTRY_EMPTY);
                if (!table)
                        return 0;
                rc = base_region3_walk(table, addr, end, 1);
                asce = table | _ASCE_TYPE_REGION3 | _ASCE_TABLE_LENGTH;
        } else if (end <= _REGION1_SIZE) {
                table = base_crst_alloc(_REGION2_ENTRY_EMPTY);
                if (!table)
                        return 0;
                rc = base_region2_walk(table, addr, end, 1);
                asce = table | _ASCE_TYPE_REGION2 | _ASCE_TABLE_LENGTH;
        } else {
                table = base_crst_alloc(_REGION1_ENTRY_EMPTY);
                if (!table)
                        return 0;
                rc = base_region1_walk(table, addr, end, 1);
                asce = table | _ASCE_TYPE_REGION1 | _ASCE_TABLE_LENGTH;
        }
        if (rc) {
                base_asce_free(asce);
                asce = 0;
        }
        return asce;
}