// 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/page-states.h>
#include <asm/pgalloc.h>
#include <asm/tlbflush.h>

unsigned long *crst_table_alloc_noprof(struct mm_struct *mm)
{
        gfp_t gfp = GFP_KERNEL_ACCOUNT;
        struct ptdesc *ptdesc;
        unsigned long *table;

        if (mm == &init_mm)
                gfp &= ~__GFP_ACCOUNT;
        ptdesc = pagetable_alloc_noprof(gfp, CRST_ALLOC_ORDER);
        if (!ptdesc)
                return NULL;
        table = ptdesc_address(ptdesc);
        __arch_set_page_dat(table, 1UL << CRST_ALLOC_ORDER);
        return table;
}

void crst_table_free(struct mm_struct *mm, unsigned long *table)
{
        if (!table)
                return;
        pagetable_free(virt_to_ptdesc(table));
}

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

        /* change all active ASCEs to avoid the creation of new TLBs */
        if (current->active_mm == mm) {
                asce.val = mm->context.asce;
                get_lowcore()->user_asce = asce;
                local_ctl_load(7, &asce);
                if (!test_thread_flag(TIF_ASCE_PRIMARY))
                        local_ctl_load(1, &asce);
        }
        __tlb_flush_local();
}

int crst_table_upgrade(struct mm_struct *mm, unsigned long end)
{
        unsigned long *pgd = NULL, *p4d = NULL, *__pgd;
        unsigned long asce_limit = mm->context.asce_limit;

        mmap_assert_write_locked(mm);

        /* upgrade should only happen from 3 to 4, 3 to 5, or 4 to 5 levels */
        VM_BUG_ON(asce_limit < _REGION2_SIZE);

        if (end <= asce_limit)
                return 0;

        if (asce_limit == _REGION2_SIZE) {
                p4d = crst_table_alloc(mm);
                if (unlikely(!p4d))
                        goto err_p4d;
                crst_table_init(p4d, _REGION2_ENTRY_EMPTY);
                pagetable_p4d_ctor(virt_to_ptdesc(p4d));
        }
        if (end > _REGION1_SIZE) {
                pgd = crst_table_alloc(mm);
                if (unlikely(!pgd))
                        goto err_pgd;
                crst_table_init(pgd, _REGION1_ENTRY_EMPTY);
                pagetable_pgd_ctor(virt_to_ptdesc(pgd));
        }

        spin_lock_bh(&mm->page_table_lock);

        if (p4d) {
                __pgd = (unsigned long *) mm->pgd;
                p4d_populate(mm, (p4d_t *) p4d, (pud_t *) __pgd);
                mm->pgd = (pgd_t *) p4d;
                mm->context.asce_limit = _REGION1_SIZE;
                mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH |
                        _ASCE_USER_BITS | _ASCE_TYPE_REGION2;
                mm_inc_nr_puds(mm);
        }
        if (pgd) {
                __pgd = (unsigned long *) mm->pgd;
                pgd_populate(mm, (pgd_t *) pgd, (p4d_t *) __pgd);
                mm->pgd = (pgd_t *) pgd;
                mm->context.asce_limit = TASK_SIZE_MAX;
                mm->context.asce = __pa(mm->pgd) | _ASCE_TABLE_LENGTH |
                        _ASCE_USER_BITS | _ASCE_TYPE_REGION1;
        }

        spin_unlock_bh(&mm->page_table_lock);

        on_each_cpu(__crst_table_upgrade, mm, 0);

        return 0;

err_pgd:
        pagetable_dtor(virt_to_ptdesc(p4d));
        crst_table_free(mm, p4d);
err_p4d:
        return -ENOMEM;
}

unsigned long *page_table_alloc_noprof(struct mm_struct *mm)
{
        gfp_t gfp = GFP_KERNEL_ACCOUNT;
        struct ptdesc *ptdesc;
        unsigned long *table;

        if (mm == &init_mm)
                gfp &= ~__GFP_ACCOUNT;
        ptdesc = pagetable_alloc_noprof(gfp, 0);
        if (!ptdesc)
                return NULL;
        if (!pagetable_pte_ctor(mm, ptdesc)) {
                pagetable_free(ptdesc);
                return NULL;
        }
        table = ptdesc_address(ptdesc);
        __arch_set_page_dat(table, 1);
        memset64((u64 *)table, _PAGE_INVALID, PTRS_PER_PTE);
        memset64((u64 *)table + PTRS_PER_PTE, 0, PTRS_PER_PTE);
        return table;
}

void page_table_free(struct mm_struct *mm, unsigned long *table)
{
        struct ptdesc *ptdesc = virt_to_ptdesc(table);

        if (pagetable_is_reserved(ptdesc))
                return free_reserved_ptdesc(ptdesc);
        pagetable_dtor_free(ptdesc);
}

#ifdef CONFIG_TRANSPARENT_HUGEPAGE
static void pte_free_now(struct rcu_head *head)
{
        struct ptdesc *ptdesc = container_of(head, struct ptdesc, pt_rcu_head);

        pagetable_dtor_free(ptdesc);
}

void pte_free_defer(struct mm_struct *mm, pgtable_t pgtable)
{
        struct ptdesc *ptdesc = virt_to_ptdesc(pgtable);

        call_rcu(&ptdesc->pt_rcu_head, pte_free_now);
}
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */

/*
 * 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)
{
        unsigned long *table;

        table = kmem_cache_alloc(base_pgt_cache, GFP_KERNEL);
        if (table)
                memset64((u64 *)table, _PAGE_INVALID, PTRS_PER_PTE);
        return table;
}

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

static unsigned long *base_crst_alloc(unsigned long val)
{
        unsigned long *table;
        struct ptdesc *ptdesc;

        ptdesc = pagetable_alloc(GFP_KERNEL, CRST_ALLOC_ORDER);
        if (!ptdesc)
                return NULL;
        table = ptdesc_address(ptdesc);
        crst_table_init(table, val);
        return table;
}

static void base_crst_free(unsigned long *table)
{
        if (!table)
                return;
        pagetable_free(virt_to_ptdesc(table));
}

#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)"
                : "=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 = 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 = 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 = __pa(table) | _SEGMENT_ENTRY;
                }
                table = __va(*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 = 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 = __pa(table) | _REGION3_ENTRY;
                }
                table = __va(*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 = 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 = __pa(table) | _REGION2_ENTRY;
                }
                table = __va(*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 = 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 = __pa(table) | _REGION1_ENTRY;
                }
                table = __va(*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 = __va(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, TASK_SIZE_MAX, 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 = __pa(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 = __pa(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 = __pa(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 = __pa(table) | _ASCE_TYPE_REGION1 | _ASCE_TABLE_LENGTH;
        }
        if (rc) {
                base_asce_free(asce);
                asce = 0;
        }
        return asce;
}