/*
 * PPC64 (POWER4) Huge TLB Page Support for Kernel.
 *
 * Copyright (C) 2003 David Gibson, IBM Corporation.
 *
 * Based on the IA-32 version:
 * Copyright (C) 2002, Rohit Seth <rohit.seth@intel.com>
 */

#include <linux/init.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/hugetlb.h>
#include <linux/pagemap.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/sysctl.h>
#include <asm/mman.h>
#include <asm/pgalloc.h>
#include <asm/tlb.h>
#include <asm/tlbflush.h>
#include <asm/mmu_context.h>
#include <asm/machdep.h>
#include <asm/cputable.h>
#include <asm/spu.h>

#define NUM_LOW_AREAS   (0x100000000UL >> SID_SHIFT)
#define NUM_HIGH_AREAS  (PGTABLE_RANGE >> HTLB_AREA_SHIFT)

#ifdef CONFIG_PPC_64K_PAGES
#define HUGEPTE_INDEX_SIZE      (PMD_SHIFT-HPAGE_SHIFT)
#else
#define HUGEPTE_INDEX_SIZE      (PUD_SHIFT-HPAGE_SHIFT)
#endif
#define PTRS_PER_HUGEPTE        (1 << HUGEPTE_INDEX_SIZE)
#define HUGEPTE_TABLE_SIZE      (sizeof(pte_t) << HUGEPTE_INDEX_SIZE)

#define HUGEPD_SHIFT            (HPAGE_SHIFT + HUGEPTE_INDEX_SIZE)
#define HUGEPD_SIZE             (1UL << HUGEPD_SHIFT)
#define HUGEPD_MASK             (~(HUGEPD_SIZE-1))

#define huge_pgtable_cache      (pgtable_cache[HUGEPTE_CACHE_NUM])

/* Flag to mark huge PD pointers.  This means pmd_bad() and pud_bad()
 * will choke on pointers to hugepte tables, which is handy for
 * catching screwups early. */
#define HUGEPD_OK       0x1

typedef struct { unsigned long pd; } hugepd_t;

#define hugepd_none(hpd)        ((hpd).pd == 0)

static inline pte_t *hugepd_page(hugepd_t hpd)
{
        BUG_ON(!(hpd.pd & HUGEPD_OK));
        return (pte_t *)(hpd.pd & ~HUGEPD_OK);
}

static inline pte_t *hugepte_offset(hugepd_t *hpdp, unsigned long addr)
{
        unsigned long idx = ((addr >> HPAGE_SHIFT) & (PTRS_PER_HUGEPTE-1));
        pte_t *dir = hugepd_page(*hpdp);

        return dir + idx;
}

static int __hugepte_alloc(struct mm_struct *mm, hugepd_t *hpdp,
                           unsigned long address)
{
        pte_t *new = kmem_cache_alloc(huge_pgtable_cache,
                                      GFP_KERNEL|__GFP_REPEAT);

        if (! new)
                return -ENOMEM;

        spin_lock(&mm->page_table_lock);
        if (!hugepd_none(*hpdp))
                kmem_cache_free(huge_pgtable_cache, new);
        else
                hpdp->pd = (unsigned long)new | HUGEPD_OK;
        spin_unlock(&mm->page_table_lock);
        return 0;
}

/* Modelled after find_linux_pte() */
pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr)
{
        pgd_t *pg;
        pud_t *pu;

        BUG_ON(get_slice_psize(mm, addr) != mmu_huge_psize);

        addr &= HPAGE_MASK;

        pg = pgd_offset(mm, addr);
        if (!pgd_none(*pg)) {
                pu = pud_offset(pg, addr);
                if (!pud_none(*pu)) {
#ifdef CONFIG_PPC_64K_PAGES
                        pmd_t *pm;
                        pm = pmd_offset(pu, addr);
                        if (!pmd_none(*pm))
                                return hugepte_offset((hugepd_t *)pm, addr);
#else
                        return hugepte_offset((hugepd_t *)pu, addr);
#endif
                }
        }

        return NULL;
}

pte_t *huge_pte_alloc(struct mm_struct *mm, unsigned long addr)
{
        pgd_t *pg;
        pud_t *pu;
        hugepd_t *hpdp = NULL;

        BUG_ON(get_slice_psize(mm, addr) != mmu_huge_psize);

        addr &= HPAGE_MASK;

        pg = pgd_offset(mm, addr);
        pu = pud_alloc(mm, pg, addr);

        if (pu) {
#ifdef CONFIG_PPC_64K_PAGES
                pmd_t *pm;
                pm = pmd_alloc(mm, pu, addr);
                if (pm)
                        hpdp = (hugepd_t *)pm;
#else
                hpdp = (hugepd_t *)pu;
#endif
        }

        if (! hpdp)
                return NULL;

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

        return hugepte_offset(hpdp, addr);
}

int huge_pmd_unshare(struct mm_struct *mm, unsigned long *addr, pte_t *ptep)
{
        return 0;
}

static void free_hugepte_range(struct mmu_gather *tlb, hugepd_t *hpdp)
{
        pte_t *hugepte = hugepd_page(*hpdp);

        hpdp->pd = 0;
        tlb->need_flush = 1;
        pgtable_free_tlb(tlb, pgtable_free_cache(hugepte, HUGEPTE_CACHE_NUM,
                                                 PGF_CACHENUM_MASK));
}

#ifdef CONFIG_PPC_64K_PAGES
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;
        pmd = pmd_offset(pud, addr);
        do {
                next = pmd_addr_end(addr, end);
                if (pmd_none(*pmd))
                        continue;
                free_hugepte_range(tlb, (hugepd_t *)pmd);
        } while (pmd++, addr = next, addr != end);

        start &= PUD_MASK;
        if (start < floor)
                return;
        if (ceiling) {
                ceiling &= PUD_MASK;
                if (!ceiling)
                        return;
        }
        if (end - 1 > ceiling - 1)
                return;

        pmd = pmd_offset(pud, start);
        pud_clear(pud);
        pmd_free_tlb(tlb, pmd);
}
#endif

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

        start = addr;
        pud = pud_offset(pgd, addr);
        do {
                next = pud_addr_end(addr, end);
#ifdef CONFIG_PPC_64K_PAGES
                if (pud_none_or_clear_bad(pud))
                        continue;
                hugetlb_free_pmd_range(tlb, pud, addr, next, floor, ceiling);
#else
                if (pud_none(*pud))
                        continue;
                free_hugepte_range(tlb, (hugepd_t *)pud);
#endif
        } while (pud++, addr = next, addr != end);

        start &= PGDIR_MASK;
        if (start < floor)
                return;
        if (ceiling) {
                ceiling &= PGDIR_MASK;
                if (!ceiling)
                        return;
        }
        if (end - 1 > ceiling - 1)
                return;

        pud = pud_offset(pgd, start);
        pgd_clear(pgd);
        pud_free_tlb(tlb, pud);
}

/*
 * This function frees user-level page tables of a process.
 *
 * Must be called with pagetable lock held.
 */
void hugetlb_free_pgd_range(struct mmu_gather **tlb,
                            unsigned long addr, unsigned long end,
                            unsigned long floor, unsigned long ceiling)
{
        pgd_t *pgd;
        unsigned long next;
        unsigned long start;

        /*
         * Comments below take from the normal free_pgd_range().  They
         * apply here too.  The tests against HUGEPD_MASK below are
         * essential, because we *don't* test for this at the bottom
         * level.  Without them we'll attempt to free a hugepte table
         * when we unmap just part of it, even if there are other
         * active mappings using it.
         *
         * The next few lines have given us lots of grief...
         *
         * Why are we testing HUGEPD* at this top level?  Because
         * often there will be no work to do at all, and we'd prefer
         * not to go all the way down to the bottom just to discover
         * that.
         *
         * Why all these "- 1"s?  Because 0 represents both the bottom
         * of the address space and the top of it (using -1 for the
         * top wouldn't help much: the masks would do the wrong thing).
         * The rule is that addr 0 and floor 0 refer to the bottom of
         * the address space, but end 0 and ceiling 0 refer to the top
         * Comparisons need to use "end - 1" and "ceiling - 1" (though
         * that end 0 case should be mythical).
         *
         * Wherever addr is brought up or ceiling brought down, we
         * must be careful to reject "the opposite 0" before it
         * confuses the subsequent tests.  But what about where end is
         * brought down by HUGEPD_SIZE below? no, end can't go down to
         * 0 there.
         *
         * Whereas we round start (addr) and ceiling down, by different
         * masks at different levels, in order to test whether a table
         * now has no other vmas using it, so can be freed, we don't
         * bother to round floor or end up - the tests don't need that.
         */

        addr &= HUGEPD_MASK;
        if (addr < floor) {
                addr += HUGEPD_SIZE;
                if (!addr)
                        return;
        }
        if (ceiling) {
                ceiling &= HUGEPD_MASK;
                if (!ceiling)
                        return;
        }
        if (end - 1 > ceiling - 1)
                end -= HUGEPD_SIZE;
        if (addr > end - 1)
                return;

        start = addr;
        pgd = pgd_offset((*tlb)->mm, addr);
        do {
                BUG_ON(get_slice_psize((*tlb)->mm, addr) != mmu_huge_psize);
                next = pgd_addr_end(addr, end);
                if (pgd_none_or_clear_bad(pgd))
                        continue;
                hugetlb_free_pud_range(*tlb, pgd, addr, next, floor, ceiling);
        } while (pgd++, addr = next, addr != end);
}

void set_huge_pte_at(struct mm_struct *mm, unsigned long addr,
                     pte_t *ptep, pte_t pte)
{
        if (pte_present(*ptep)) {
                /* We open-code pte_clear because we need to pass the right
                 * argument to hpte_need_flush (huge / !huge). Might not be
                 * necessary anymore if we make hpte_need_flush() get the
                 * page size from the slices
                 */
                pte_update(mm, addr & HPAGE_MASK, ptep, ~0UL, 1);
        }
        *ptep = __pte(pte_val(pte) & ~_PAGE_HPTEFLAGS);
}

pte_t huge_ptep_get_and_clear(struct mm_struct *mm, unsigned long addr,
                              pte_t *ptep)
{
        unsigned long old = pte_update(mm, addr, ptep, ~0UL, 1);
        return __pte(old);
}

struct page *
follow_huge_addr(struct mm_struct *mm, unsigned long address, int write)
{
        pte_t *ptep;
        struct page *page;

        if (get_slice_psize(mm, address) != mmu_huge_psize)
                return ERR_PTR(-EINVAL);

        ptep = huge_pte_offset(mm, address);
        page = pte_page(*ptep);
        if (page)
                page += (address % HPAGE_SIZE) / PAGE_SIZE;

        return page;
}

int pmd_huge(pmd_t pmd)
{
        return 0;
}

struct page *
follow_huge_pmd(struct mm_struct *mm, unsigned long address,
                pmd_t *pmd, int write)
{
        BUG();
        return NULL;
}


unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
                                        unsigned long len, unsigned long pgoff,
                                        unsigned long flags)
{
        return slice_get_unmapped_area(addr, len, flags,
                                       mmu_huge_psize, 1, 0);
}

/*
 * Called by asm hashtable.S for doing lazy icache flush
 */
static unsigned int hash_huge_page_do_lazy_icache(unsigned long rflags,
                                                  pte_t pte, int trap)
{
        struct page *page;
        int i;

        if (!pfn_valid(pte_pfn(pte)))
                return rflags;

        page = pte_page(pte);

        /* page is dirty */
        if (!test_bit(PG_arch_1, &page->flags) && !PageReserved(page)) {
                if (trap == 0x400) {
                        for (i = 0; i < (HPAGE_SIZE / PAGE_SIZE); i++)
                                __flush_dcache_icache(page_address(page+i));
                        set_bit(PG_arch_1, &page->flags);
                } else {
                        rflags |= HPTE_R_N;
                }
        }
        return rflags;
}

int hash_huge_page(struct mm_struct *mm, unsigned long access,
                   unsigned long ea, unsigned long vsid, int local,
                   unsigned long trap)
{
        pte_t *ptep;
        unsigned long old_pte, new_pte;
        unsigned long va, rflags, pa;
        long slot;
        int err = 1;
        int ssize = user_segment_size(ea);

        ptep = huge_pte_offset(mm, ea);

        /* Search the Linux page table for a match with va */
        va = hpt_va(ea, vsid, ssize);

        /*
         * If no pte found or not present, send the problem up to
         * do_page_fault
         */
        if (unlikely(!ptep || pte_none(*ptep)))
                goto out;

        /* 
         * Check the user's access rights to the page.  If access should be
         * prevented then send the problem up to do_page_fault.
         */
        if (unlikely(access & ~pte_val(*ptep)))
                goto out;
        /*
         * At this point, we have a pte (old_pte) which can be used to build
         * or update an HPTE. There are 2 cases:
         *
         * 1. There is a valid (present) pte with no associated HPTE (this is 
         *      the most common case)
         * 2. There is a valid (present) pte with an associated HPTE. The
         *      current values of the pp bits in the HPTE prevent access
         *      because we are doing software DIRTY bit management and the
         *      page is currently not DIRTY. 
         */


        do {
                old_pte = pte_val(*ptep);
                if (old_pte & _PAGE_BUSY)
                        goto out;
                new_pte = old_pte | _PAGE_BUSY |
                        _PAGE_ACCESSED | _PAGE_HASHPTE;
        } while(old_pte != __cmpxchg_u64((unsigned long *)ptep,
                                         old_pte, new_pte));

        rflags = 0x2 | (!(new_pte & _PAGE_RW));
        /* _PAGE_EXEC -> HW_NO_EXEC since it's inverted */
        rflags |= ((new_pte & _PAGE_EXEC) ? 0 : HPTE_R_N);
        if (!cpu_has_feature(CPU_FTR_COHERENT_ICACHE))
                /* No CPU has hugepages but lacks no execute, so we
                 * don't need to worry about that case */
                rflags = hash_huge_page_do_lazy_icache(rflags, __pte(old_pte),
                                                       trap);

        /* Check if pte already has an hpte (case 2) */
        if (unlikely(old_pte & _PAGE_HASHPTE)) {
                /* There MIGHT be an HPTE for this pte */
                unsigned long hash, slot;

                hash = hpt_hash(va, HPAGE_SHIFT, ssize);
                if (old_pte & _PAGE_F_SECOND)
                        hash = ~hash;
                slot = (hash & htab_hash_mask) * HPTES_PER_GROUP;
                slot += (old_pte & _PAGE_F_GIX) >> 12;

                if (ppc_md.hpte_updatepp(slot, rflags, va, mmu_huge_psize,
                                         ssize, local) == -1)
                        old_pte &= ~_PAGE_HPTEFLAGS;
        }

        if (likely(!(old_pte & _PAGE_HASHPTE))) {
                unsigned long hash = hpt_hash(va, HPAGE_SHIFT, ssize);
                unsigned long hpte_group;

                pa = pte_pfn(__pte(old_pte)) << PAGE_SHIFT;

repeat:
                hpte_group = ((hash & htab_hash_mask) *
                              HPTES_PER_GROUP) & ~0x7UL;

                /* clear HPTE slot informations in new PTE */
                new_pte = (new_pte & ~_PAGE_HPTEFLAGS) | _PAGE_HASHPTE;

                /* Add in WIMG bits */
                /* XXX We should store these in the pte */
                /* --BenH: I think they are ... */
                rflags |= _PAGE_COHERENT;

                /* Insert into the hash table, primary slot */
                slot = ppc_md.hpte_insert(hpte_group, va, pa, rflags, 0,
                                          mmu_huge_psize, ssize);

                /* Primary is full, try the secondary */
                if (unlikely(slot == -1)) {
                        hpte_group = ((~hash & htab_hash_mask) *
                                      HPTES_PER_GROUP) & ~0x7UL; 
                        slot = ppc_md.hpte_insert(hpte_group, va, pa, rflags,
                                                  HPTE_V_SECONDARY,
                                                  mmu_huge_psize, ssize);
                        if (slot == -1) {
                                if (mftb() & 0x1)
                                        hpte_group = ((hash & htab_hash_mask) *
                                                      HPTES_PER_GROUP)&~0x7UL;

                                ppc_md.hpte_remove(hpte_group);
                                goto repeat;
                        }
                }

                if (unlikely(slot == -2))
                        panic("hash_huge_page: pte_insert failed\n");

                new_pte |= (slot << 12) & (_PAGE_F_SECOND | _PAGE_F_GIX);
        }

        /*
         * No need to use ldarx/stdcx here
         */
        *ptep = __pte(new_pte & ~_PAGE_BUSY);

        err = 0;

 out:
        return err;
}

static void zero_ctor(struct kmem_cache *cache, void *addr)
{
        memset(addr, 0, kmem_cache_size(cache));
}

static int __init hugetlbpage_init(void)
{
        if (!cpu_has_feature(CPU_FTR_16M_PAGE))
                return -ENODEV;

        huge_pgtable_cache = kmem_cache_create("hugepte_cache",
                                               HUGEPTE_TABLE_SIZE,
                                               HUGEPTE_TABLE_SIZE,
                                               0,
                                               zero_ctor);
        if (! huge_pgtable_cache)
                panic("hugetlbpage_init(): could not create hugepte cache\n");

        return 0;
}

module_init(hugetlbpage_init);