/*
 * PPC Huge TLB Page Support for Kernel.
 *
 * Copyright (C) 2003 David Gibson, IBM Corporation.
 * Copyright (C) 2011 Becky Bruce, Freescale Semiconductor
 *
 * Based on the IA-32 version:
 * Copyright (C) 2002, Rohit Seth <rohit.seth@intel.com>
 */

#include <linux/mm.h>
#include <linux/io.h>
#include <linux/slab.h>
#include <linux/hugetlb.h>
#include <linux/export.h>
#include <linux/of_fdt.h>
#include <linux/memblock.h>
#include <linux/moduleparam.h>
#include <linux/swap.h>
#include <linux/swapops.h>
#include <linux/kmemleak.h>
#include <asm/pgalloc.h>
#include <asm/tlb.h>
#include <asm/setup.h>
#include <asm/hugetlb.h>
#include <asm/pte-walk.h>

bool hugetlb_disabled = false;

#define hugepd_none(hpd)        (hpd_val(hpd) == 0)

#define PTE_T_ORDER     (__builtin_ffs(sizeof(pte_basic_t)) - \
                         __builtin_ffs(sizeof(void *)))

pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr, unsigned long sz)
{
        /*
         * Only called for hugetlbfs pages, hence can ignore THP and the
         * irq disabled walk.
         */
        return __find_linux_pte(mm->pgd, addr, NULL, NULL);
}

static int __hugepte_alloc(struct mm_struct *mm, hugepd_t *hpdp,
                           unsigned long address, unsigned int pdshift,
                           unsigned int pshift, spinlock_t *ptl)
{
        struct kmem_cache *cachep;
        pte_t *new;
        int i;
        int num_hugepd;

        if (pshift >= pdshift) {
                cachep = PGT_CACHE(PTE_T_ORDER);
                num_hugepd = 1 << (pshift - pdshift);
        } else {
                cachep = PGT_CACHE(pdshift - pshift);
                num_hugepd = 1;
        }

        if (!cachep) {
                WARN_ONCE(1, "No page table cache created for hugetlb tables");
                return -ENOMEM;
        }

        new = kmem_cache_alloc(cachep, pgtable_gfp_flags(mm, GFP_KERNEL));

        BUG_ON(pshift > HUGEPD_SHIFT_MASK);
        BUG_ON((unsigned long)new & HUGEPD_SHIFT_MASK);

        if (!new)
                return -ENOMEM;

        /*
         * Make sure other cpus find the hugepd set only after a
         * properly initialized page table is visible to them.
         * For more details look for comment in __pte_alloc().
         */
        smp_wmb();

        spin_lock(ptl);
        /*
         * We have multiple higher-level entries that point to the same
         * actual pte location.  Fill in each as we go and backtrack on error.
         * We need all of these so the DTLB pgtable walk code can find the
         * right higher-level entry without knowing if it's a hugepage or not.
         */
        for (i = 0; i < num_hugepd; i++, hpdp++) {
                if (unlikely(!hugepd_none(*hpdp)))
                        break;
                hugepd_populate(hpdp, new, pshift);
        }
        /* If we bailed from the for loop early, an error occurred, clean up */
        if (i < num_hugepd) {
                for (i = i - 1 ; i >= 0; i--, hpdp--)
                        *hpdp = __hugepd(0);
                kmem_cache_free(cachep, new);
        } else {
                kmemleak_ignore(new);
        }
        spin_unlock(ptl);
        return 0;
}

/*
 * At this point we do the placement change only for BOOK3S 64. This would
 * possibly work on other subarchs.
 */
pte_t *huge_pte_alloc(struct mm_struct *mm, struct vm_area_struct *vma,
                      unsigned long addr, unsigned long sz)
{
        pgd_t *pg;
        p4d_t *p4;
        pud_t *pu;
        pmd_t *pm;
        hugepd_t *hpdp = NULL;
        unsigned pshift = __ffs(sz);
        unsigned pdshift = PGDIR_SHIFT;
        spinlock_t *ptl;

        addr &= ~(sz-1);
        pg = pgd_offset(mm, addr);
        p4 = p4d_offset(pg, addr);

#ifdef CONFIG_PPC_BOOK3S_64
        if (pshift == PGDIR_SHIFT)
                /* 16GB huge page */
                return (pte_t *) p4;
        else if (pshift > PUD_SHIFT) {
                /*
                 * We need to use hugepd table
                 */
                ptl = &mm->page_table_lock;
                hpdp = (hugepd_t *)p4;
        } else {
                pdshift = PUD_SHIFT;
                pu = pud_alloc(mm, p4, addr);
                if (!pu)
                        return NULL;
                if (pshift == PUD_SHIFT)
                        return (pte_t *)pu;
                else if (pshift > PMD_SHIFT) {
                        ptl = pud_lockptr(mm, pu);
                        hpdp = (hugepd_t *)pu;
                } else {
                        pdshift = PMD_SHIFT;
                        pm = pmd_alloc(mm, pu, addr);
                        if (!pm)
                                return NULL;
                        if (pshift == PMD_SHIFT)
                                /* 16MB hugepage */
                                return (pte_t *)pm;
                        else {
                                ptl = pmd_lockptr(mm, pm);
                                hpdp = (hugepd_t *)pm;
                        }
                }
        }
#else
        if (pshift >= PGDIR_SHIFT) {
                ptl = &mm->page_table_lock;
                hpdp = (hugepd_t *)p4;
        } else {
                pdshift = PUD_SHIFT;
                pu = pud_alloc(mm, p4, addr);
                if (!pu)
                        return NULL;
                if (pshift >= PUD_SHIFT) {
                        ptl = pud_lockptr(mm, pu);
                        hpdp = (hugepd_t *)pu;
                } else {
                        pdshift = PMD_SHIFT;
                        pm = pmd_alloc(mm, pu, addr);
                        if (!pm)
                                return NULL;
                        ptl = pmd_lockptr(mm, pm);
                        hpdp = (hugepd_t *)pm;
                }
        }
#endif
        if (!hpdp)
                return NULL;

        if (IS_ENABLED(CONFIG_PPC_8xx) && pshift < PMD_SHIFT)
                return pte_alloc_map(mm, (pmd_t *)hpdp, addr);

        BUG_ON(!hugepd_none(*hpdp) && !hugepd_ok(*hpdp));

        if (hugepd_none(*hpdp) && __hugepte_alloc(mm, hpdp, addr,
                                                  pdshift, pshift, ptl))
                return NULL;

        return hugepte_offset(*hpdp, addr, pdshift);
}

#ifdef CONFIG_PPC_BOOK3S_64
/*
 * Tracks gpages after the device tree is scanned and before the
 * huge_boot_pages list is ready on pseries.
 */
#define MAX_NUMBER_GPAGES       1024
__initdata static u64 gpage_freearray[MAX_NUMBER_GPAGES];
__initdata static unsigned nr_gpages;

/*
 * Build list of addresses of gigantic pages.  This function is used in early
 * boot before the buddy allocator is setup.
 */
void __init pseries_add_gpage(u64 addr, u64 page_size, unsigned long number_of_pages)
{
        if (!addr)
                return;
        while (number_of_pages > 0) {
                gpage_freearray[nr_gpages] = addr;
                nr_gpages++;
                number_of_pages--;
                addr += page_size;
        }
}

static int __init pseries_alloc_bootmem_huge_page(struct hstate *hstate)
{
        struct huge_bootmem_page *m;
        if (nr_gpages == 0)
                return 0;
        m = phys_to_virt(gpage_freearray[--nr_gpages]);
        gpage_freearray[nr_gpages] = 0;
        list_add(&m->list, &huge_boot_pages);
        m->hstate = hstate;
        return 1;
}

bool __init hugetlb_node_alloc_supported(void)
{
        return false;
}
#endif


int __init alloc_bootmem_huge_page(struct hstate *h, int nid)
{

#ifdef CONFIG_PPC_BOOK3S_64
        if (firmware_has_feature(FW_FEATURE_LPAR) && !radix_enabled())
                return pseries_alloc_bootmem_huge_page(h);
#endif
        return __alloc_bootmem_huge_page(h, nid);
}

#ifndef CONFIG_PPC_BOOK3S_64
#define HUGEPD_FREELIST_SIZE \
        ((PAGE_SIZE - sizeof(struct hugepd_freelist)) / sizeof(pte_t))

struct hugepd_freelist {
        struct rcu_head rcu;
        unsigned int index;
        void *ptes[];
};

static DEFINE_PER_CPU(struct hugepd_freelist *, hugepd_freelist_cur);

static void hugepd_free_rcu_callback(struct rcu_head *head)
{
        struct hugepd_freelist *batch =
                container_of(head, struct hugepd_freelist, rcu);
        unsigned int i;

        for (i = 0; i < batch->index; i++)
                kmem_cache_free(PGT_CACHE(PTE_T_ORDER), batch->ptes[i]);

        free_page((unsigned long)batch);
}

static void hugepd_free(struct mmu_gather *tlb, void *hugepte)
{
        struct hugepd_freelist **batchp;

        batchp = &get_cpu_var(hugepd_freelist_cur);

        if (atomic_read(&tlb->mm->mm_users) < 2 ||
            mm_is_thread_local(tlb->mm)) {
                kmem_cache_free(PGT_CACHE(PTE_T_ORDER), hugepte);
                put_cpu_var(hugepd_freelist_cur);
                return;
        }

        if (*batchp == NULL) {
                *batchp = (struct hugepd_freelist *)__get_free_page(GFP_ATOMIC);
                (*batchp)->index = 0;
        }

        (*batchp)->ptes[(*batchp)->index++] = hugepte;
        if ((*batchp)->index == HUGEPD_FREELIST_SIZE) {
                call_rcu(&(*batchp)->rcu, hugepd_free_rcu_callback);
                *batchp = NULL;
        }
        put_cpu_var(hugepd_freelist_cur);
}
#else
static inline void hugepd_free(struct mmu_gather *tlb, void *hugepte) {}
#endif

/* Return true when the entry to be freed maps more than the area being freed */
static bool range_is_outside_limits(unsigned long start, unsigned long end,
                                    unsigned long floor, unsigned long ceiling,
                                    unsigned long mask)
{
        if ((start & mask) < floor)
                return true;
        if (ceiling) {
                ceiling &= mask;
                if (!ceiling)
                        return true;
        }
        return end - 1 > ceiling - 1;
}

static void free_hugepd_range(struct mmu_gather *tlb, hugepd_t *hpdp, int pdshift,
                              unsigned long start, unsigned long end,
                              unsigned long floor, unsigned long ceiling)
{
        pte_t *hugepte = hugepd_page(*hpdp);
        int i;

        unsigned long pdmask = ~((1UL << pdshift) - 1);
        unsigned int num_hugepd = 1;
        unsigned int shift = hugepd_shift(*hpdp);

        /* Note: On fsl the hpdp may be the first of several */
        if (shift > pdshift)
                num_hugepd = 1 << (shift - pdshift);

        if (range_is_outside_limits(start, end, floor, ceiling, pdmask))
                return;

        for (i = 0; i < num_hugepd; i++, hpdp++)
                *hpdp = __hugepd(0);

        if (shift >= pdshift)
                hugepd_free(tlb, hugepte);
        else
                pgtable_free_tlb(tlb, hugepte,
                                 get_hugepd_cache_index(pdshift - shift));
}

static void hugetlb_free_pte_range(struct mmu_gather *tlb, pmd_t *pmd,
                                   unsigned long addr, unsigned long end,
                                   unsigned long floor, unsigned long ceiling)
{
        pgtable_t token = pmd_pgtable(*pmd);

        if (range_is_outside_limits(addr, end, floor, ceiling, PMD_MASK))
                return;

        pmd_clear(pmd);
        pte_free_tlb(tlb, token, addr);
        mm_dec_nr_ptes(tlb->mm);
}

static void hugetlb_free_pmd_range(struct mmu_gather *tlb, pud_t *pud,
                                   unsigned long addr, unsigned long end,
                                   unsigned long floor, unsigned long ceiling)
{
        pmd_t *pmd;
        unsigned long next;
        unsigned long start;

        start = addr;
        do {
                unsigned long more;

                pmd = pmd_offset(pud, addr);
                next = pmd_addr_end(addr, end);
                if (!is_hugepd(__hugepd(pmd_val(*pmd)))) {
                        if (pmd_none_or_clear_bad(pmd))
                                continue;

                        /*
                         * if it is not hugepd pointer, we should already find
                         * it cleared.
                         */
                        WARN_ON(!IS_ENABLED(CONFIG_PPC_8xx));

                        hugetlb_free_pte_range(tlb, pmd, addr, end, floor, ceiling);

                        continue;
                }
                /*
                 * Increment next by the size of the huge mapping since
                 * there may be more than one entry at this level for a
                 * single hugepage, but all of them point to
                 * the same kmem cache that holds the hugepte.
                 */
                more = addr + (1 << hugepd_shift(*(hugepd_t *)pmd));
                if (more > next)
                        next = more;

                free_hugepd_range(tlb, (hugepd_t *)pmd, PMD_SHIFT,
                                  addr, next, floor, ceiling);
        } while (addr = next, addr != end);

        if (range_is_outside_limits(start, end, floor, ceiling, PUD_MASK))
                return;

        pmd = pmd_offset(pud, start & PUD_MASK);
        pud_clear(pud);
        pmd_free_tlb(tlb, pmd, start & PUD_MASK);
        mm_dec_nr_pmds(tlb->mm);
}

static void hugetlb_free_pud_range(struct mmu_gather *tlb, p4d_t *p4d,
                                   unsigned long addr, unsigned long end,
                                   unsigned long floor, unsigned long ceiling)
{
        pud_t *pud;
        unsigned long next;
        unsigned long start;

        start = addr;
        do {
                pud = pud_offset(p4d, addr);
                next = pud_addr_end(addr, end);
                if (!is_hugepd(__hugepd(pud_val(*pud)))) {
                        if (pud_none_or_clear_bad(pud))
                                continue;
                        hugetlb_free_pmd_range(tlb, pud, addr, next, floor,
                                               ceiling);
                } else {
                        unsigned long more;
                        /*
                         * Increment next by the size of the huge mapping since
                         * there may be more than one entry at this level for a
                         * single hugepage, but all of them point to
                         * the same kmem cache that holds the hugepte.
                         */
                        more = addr + (1 << hugepd_shift(*(hugepd_t *)pud));
                        if (more > next)
                                next = more;

                        free_hugepd_range(tlb, (hugepd_t *)pud, PUD_SHIFT,
                                          addr, next, floor, ceiling);
                }
        } while (addr = next, addr != end);

        if (range_is_outside_limits(start, end, floor, ceiling, PGDIR_MASK))
                return;

        pud = pud_offset(p4d, start & PGDIR_MASK);
        p4d_clear(p4d);
        pud_free_tlb(tlb, pud, start & PGDIR_MASK);
        mm_dec_nr_puds(tlb->mm);
}

/*
 * This function frees user-level page tables of a process.
 */
void hugetlb_free_pgd_range(struct mmu_gather *tlb,
                            unsigned long addr, unsigned long end,
                            unsigned long floor, unsigned long ceiling)
{
        pgd_t *pgd;
        p4d_t *p4d;
        unsigned long next;

        /*
         * Because there are a number of different possible pagetable
         * layouts for hugepage ranges, we limit knowledge of how
         * things should be laid out to the allocation path
         * (huge_pte_alloc(), above).  Everything else works out the
         * structure as it goes from information in the hugepd
         * pointers.  That means that we can't here use the
         * optimization used in the normal page free_pgd_range(), of
         * checking whether we're actually covering a large enough
         * range to have to do anything at the top level of the walk
         * instead of at the bottom.
         *
         * To make sense of this, you should probably go read the big
         * block comment at the top of the normal free_pgd_range(),
         * too.
         */

        do {
                next = pgd_addr_end(addr, end);
                pgd = pgd_offset(tlb->mm, addr);
                p4d = p4d_offset(pgd, addr);
                if (!is_hugepd(__hugepd(pgd_val(*pgd)))) {
                        if (p4d_none_or_clear_bad(p4d))
                                continue;
                        hugetlb_free_pud_range(tlb, p4d, addr, next, floor, ceiling);
                } else {
                        unsigned long more;
                        /*
                         * Increment next by the size of the huge mapping since
                         * there may be more than one entry at the pgd level
                         * for a single hugepage, but all of them point to the
                         * same kmem cache that holds the hugepte.
                         */
                        more = addr + (1 << hugepd_shift(*(hugepd_t *)pgd));
                        if (more > next)
                                next = more;

                        free_hugepd_range(tlb, (hugepd_t *)p4d, PGDIR_SHIFT,
                                          addr, next, floor, ceiling);
                }
        } while (addr = next, addr != end);
}

struct page *follow_huge_pd(struct vm_area_struct *vma,
                            unsigned long address, hugepd_t hpd,
                            int flags, int pdshift)
{
        pte_t *ptep;
        spinlock_t *ptl;
        struct page *page = NULL;
        unsigned long mask;
        int shift = hugepd_shift(hpd);
        struct mm_struct *mm = vma->vm_mm;

retry:
        /*
         * hugepage directory entries are protected by mm->page_table_lock
         * Use this instead of huge_pte_lockptr
         */
        ptl = &mm->page_table_lock;
        spin_lock(ptl);

        ptep = hugepte_offset(hpd, address, pdshift);
        if (pte_present(*ptep)) {
                mask = (1UL << shift) - 1;
                page = pte_page(*ptep);
                page += ((address & mask) >> PAGE_SHIFT);
                if (flags & FOLL_GET)
                        get_page(page);
        } else {
                if (is_hugetlb_entry_migration(*ptep)) {
                        spin_unlock(ptl);
                        __migration_entry_wait(mm, ptep, ptl);
                        goto retry;
                }
        }
        spin_unlock(ptl);
        return page;
}

bool __init arch_hugetlb_valid_size(unsigned long size)
{
        int shift = __ffs(size);
        int mmu_psize;

        /* Check that it is a page size supported by the hardware and
         * that it fits within pagetable and slice limits. */
        if (size <= PAGE_SIZE || !is_power_of_2(size))
                return false;

        mmu_psize = check_and_get_huge_psize(shift);
        if (mmu_psize < 0)
                return false;

        BUG_ON(mmu_psize_defs[mmu_psize].shift != shift);

        return true;
}

static int __init add_huge_page_size(unsigned long long size)
{
        int shift = __ffs(size);

        if (!arch_hugetlb_valid_size((unsigned long)size))
                return -EINVAL;

        hugetlb_add_hstate(shift - PAGE_SHIFT);
        return 0;
}

static int __init hugetlbpage_init(void)
{
        bool configured = false;
        int psize;

        if (hugetlb_disabled) {
                pr_info("HugeTLB support is disabled!\n");
                return 0;
        }

        if (IS_ENABLED(CONFIG_PPC_BOOK3S_64) && !radix_enabled() &&
            !mmu_has_feature(MMU_FTR_16M_PAGE))
                return -ENODEV;

        for (psize = 0; psize < MMU_PAGE_COUNT; ++psize) {
                unsigned shift;
                unsigned pdshift;

                if (!mmu_psize_defs[psize].shift)
                        continue;

                shift = mmu_psize_to_shift(psize);

#ifdef CONFIG_PPC_BOOK3S_64
                if (shift > PGDIR_SHIFT)
                        continue;
                else if (shift > PUD_SHIFT)
                        pdshift = PGDIR_SHIFT;
                else if (shift > PMD_SHIFT)
                        pdshift = PUD_SHIFT;
                else
                        pdshift = PMD_SHIFT;
#else
                if (shift < PUD_SHIFT)
                        pdshift = PMD_SHIFT;
                else if (shift < PGDIR_SHIFT)
                        pdshift = PUD_SHIFT;
                else
                        pdshift = PGDIR_SHIFT;
#endif

                if (add_huge_page_size(1ULL << shift) < 0)
                        continue;
                /*
                 * if we have pdshift and shift value same, we don't
                 * use pgt cache for hugepd.
                 */
                if (pdshift > shift) {
                        if (!IS_ENABLED(CONFIG_PPC_8xx))
                                pgtable_cache_add(pdshift - shift);
                } else if (IS_ENABLED(CONFIG_PPC_FSL_BOOK3E) ||
                           IS_ENABLED(CONFIG_PPC_8xx)) {
                        pgtable_cache_add(PTE_T_ORDER);
                }

                configured = true;
        }

        if (!configured)
                pr_info("Failed to initialize. Disabling HugeTLB");

        return 0;
}

arch_initcall(hugetlbpage_init);

void __init gigantic_hugetlb_cma_reserve(void)
{
        unsigned long order = 0;

        if (radix_enabled())
                order = PUD_SHIFT - PAGE_SHIFT;
        else if (!firmware_has_feature(FW_FEATURE_LPAR) && mmu_psize_defs[MMU_PAGE_16G].shift)
                /*
                 * For pseries we do use ibm,expected#pages for reserving 16G pages.
                 */
                order = mmu_psize_to_shift(MMU_PAGE_16G) - PAGE_SHIFT;

        if (order) {
                VM_WARN_ON(order < MAX_ORDER);
                hugetlb_cma_reserve(order);
        }
}