/*
 * Copyright IBM Corporation, 2015
 * Author Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of version 2 of the GNU Lesser General Public License
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it would be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 *
 */

#include <linux/mm.h>
#include <asm/machdep.h>
#include <asm/mmu.h>

/*
 * Return true, if the entry has a slot value which
 * the software considers as invalid.
 */
static inline bool hpte_soft_invalid(unsigned long hidx)
{
        return ((hidx & 0xfUL) == 0xfUL);
}

/*
 * index from 0 - 15
 */
bool __rpte_sub_valid(real_pte_t rpte, unsigned long index)
{
        return !(hpte_soft_invalid(__rpte_to_hidx(rpte, index)));
}

int __hash_page_4K(unsigned long ea, unsigned long access, unsigned long vsid,
                   pte_t *ptep, unsigned long trap, unsigned long flags,
                   int ssize, int subpg_prot)
{
        real_pte_t rpte;
        unsigned long hpte_group;
        unsigned int subpg_index;
        unsigned long rflags, pa;
        unsigned long old_pte, new_pte, subpg_pte;
        unsigned long vpn, hash, slot, gslot;
        unsigned long shift = mmu_psize_defs[MMU_PAGE_4K].shift;

        /*
         * atomically mark the linux large page PTE busy and dirty
         */
        do {
                pte_t pte = READ_ONCE(*ptep);

                old_pte = pte_val(pte);
                /* If PTE busy, retry the access */
                if (unlikely(old_pte & H_PAGE_BUSY))
                        return 0;
                /* If PTE permissions don't match, take page fault */
                if (unlikely(!check_pte_access(access, old_pte)))
                        return 1;
                /*
                 * Try to lock the PTE, add ACCESSED and DIRTY if it was
                 * a write access. Since this is 4K insert of 64K page size
                 * also add H_PAGE_COMBO
                 */
                new_pte = old_pte | H_PAGE_BUSY | _PAGE_ACCESSED | H_PAGE_COMBO;
                if (access & _PAGE_WRITE)
                        new_pte |= _PAGE_DIRTY;
        } while (!pte_xchg(ptep, __pte(old_pte), __pte(new_pte)));

        /*
         * Handle the subpage protection bits
         */
        subpg_pte = new_pte & ~subpg_prot;
        rflags = htab_convert_pte_flags(subpg_pte, flags);

        if (cpu_has_feature(CPU_FTR_NOEXECUTE) &&
            !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_page_do_lazy_icache(rflags, __pte(old_pte), trap);
        }

        subpg_index = (ea & (PAGE_SIZE - 1)) >> shift;
        vpn  = hpt_vpn(ea, vsid, ssize);
        rpte = __real_pte(__pte(old_pte), ptep, PTRS_PER_PTE);
        /*
         *None of the sub 4k page is hashed
         */
        if (!(old_pte & H_PAGE_HASHPTE))
                goto htab_insert_hpte;
        /*
         * Check if the pte was already inserted into the hash table
         * as a 64k HW page, and invalidate the 64k HPTE if so.
         */
        if (!(old_pte & H_PAGE_COMBO)) {
                flush_hash_page(vpn, rpte, MMU_PAGE_64K, ssize, flags);
                /*
                 * clear the old slot details from the old and new pte.
                 * On hash insert failure we use old pte value and we don't
                 * want slot information there if we have a insert failure.
                 */
                old_pte &= ~H_PAGE_HASHPTE;
                new_pte &= ~H_PAGE_HASHPTE;
                goto htab_insert_hpte;
        }
        /*
         * Check for sub page valid and update
         */
        if (__rpte_sub_valid(rpte, subpg_index)) {
                int ret;

                gslot = pte_get_hash_gslot(vpn, shift, ssize, rpte,
                                           subpg_index);
                ret = mmu_hash_ops.hpte_updatepp(gslot, rflags, vpn,
                                                 MMU_PAGE_4K, MMU_PAGE_4K,
                                                 ssize, flags);

                /*
                 * If we failed because typically the HPTE wasn't really here
                 * we try an insertion.
                 */
                if (ret == -1)
                        goto htab_insert_hpte;

                *ptep = __pte(new_pte & ~H_PAGE_BUSY);
                return 0;
        }

htab_insert_hpte:

        /*
         * Initialize all hidx entries to invalid value, the first time
         * the PTE is about to allocate a 4K HPTE.
         */
        if (!(old_pte & H_PAGE_COMBO))
                rpte.hidx = INVALID_RPTE_HIDX;

        /*
         * handle H_PAGE_4K_PFN case
         */
        if (old_pte & H_PAGE_4K_PFN) {
                /*
                 * All the sub 4k page have the same
                 * physical address.
                 */
                pa = pte_pfn(__pte(old_pte)) << HW_PAGE_SHIFT;
        } else {
                pa = pte_pfn(__pte(old_pte)) << PAGE_SHIFT;
                pa += (subpg_index << shift);
        }
        hash = hpt_hash(vpn, shift, ssize);
repeat:
        hpte_group = (hash & htab_hash_mask) * HPTES_PER_GROUP;

        /* Insert into the hash table, primary slot */
        slot = mmu_hash_ops.hpte_insert(hpte_group, vpn, pa, rflags, 0,
                                        MMU_PAGE_4K, MMU_PAGE_4K, ssize);
        /*
         * Primary is full, try the secondary
         */
        if (unlikely(slot == -1)) {
                bool soft_invalid;

                hpte_group = (~hash & htab_hash_mask) * HPTES_PER_GROUP;
                slot = mmu_hash_ops.hpte_insert(hpte_group, vpn, pa,
                                                rflags, HPTE_V_SECONDARY,
                                                MMU_PAGE_4K, MMU_PAGE_4K,
                                                ssize);

                soft_invalid = hpte_soft_invalid(slot);
                if (unlikely(soft_invalid)) {
                        /*
                         * We got a valid slot from a hardware point of view.
                         * but we cannot use it, because we use this special
                         * value; as defined by hpte_soft_invalid(), to track
                         * invalid slots. We cannot use it. So invalidate it.
                         */
                        gslot = slot & _PTEIDX_GROUP_IX;
                        mmu_hash_ops.hpte_invalidate(hpte_group + gslot, vpn,
                                                     MMU_PAGE_4K, MMU_PAGE_4K,
                                                     ssize, 0);
                }

                if (unlikely(slot == -1 || soft_invalid)) {
                        /*
                         * For soft invalid slot, let's ensure that we release a
                         * slot from the primary, with the hope that we will
                         * acquire that slot next time we try. This will ensure
                         * that we do not get the same soft-invalid slot.
                         */
                        if (soft_invalid || (mftb() & 0x1))
                                hpte_group = (hash & htab_hash_mask) * HPTES_PER_GROUP;

                        mmu_hash_ops.hpte_remove(hpte_group);
                        /*
                         * FIXME!! Should be try the group from which we removed ?
                         */
                        goto repeat;
                }
        }
        /*
         * Hypervisor failure. Restore old pte and return -1
         * similar to __hash_page_*
         */
        if (unlikely(slot == -2)) {
                *ptep = __pte(old_pte);
                hash_failure_debug(ea, access, vsid, trap, ssize,
                                   MMU_PAGE_4K, MMU_PAGE_4K, old_pte);
                return -1;
        }

        new_pte |= pte_set_hidx(ptep, rpte, subpg_index, slot, PTRS_PER_PTE);
        new_pte |= H_PAGE_HASHPTE;

        *ptep = __pte(new_pte & ~H_PAGE_BUSY);
        return 0;
}

int __hash_page_64K(unsigned long ea, unsigned long access,
                    unsigned long vsid, pte_t *ptep, unsigned long trap,
                    unsigned long flags, int ssize)
{
        real_pte_t rpte;
        unsigned long hpte_group;
        unsigned long rflags, pa;
        unsigned long old_pte, new_pte;
        unsigned long vpn, hash, slot;
        unsigned long shift = mmu_psize_defs[MMU_PAGE_64K].shift;

        /*
         * atomically mark the linux large page PTE busy and dirty
         */
        do {
                pte_t pte = READ_ONCE(*ptep);

                old_pte = pte_val(pte);
                /* If PTE busy, retry the access */
                if (unlikely(old_pte & H_PAGE_BUSY))
                        return 0;
                /* If PTE permissions don't match, take page fault */
                if (unlikely(!check_pte_access(access, old_pte)))
                        return 1;
                /*
                 * Check if PTE has the cache-inhibit bit set
                 * If so, bail out and refault as a 4k page
                 */
                if (!mmu_has_feature(MMU_FTR_CI_LARGE_PAGE) &&
                    unlikely(pte_ci(pte)))
                        return 0;
                /*
                 * Try to lock the PTE, add ACCESSED and DIRTY if it was
                 * a write access.
                 */
                new_pte = old_pte | H_PAGE_BUSY | _PAGE_ACCESSED;
                if (access & _PAGE_WRITE)
                        new_pte |= _PAGE_DIRTY;
        } while (!pte_xchg(ptep, __pte(old_pte), __pte(new_pte)));

        rflags = htab_convert_pte_flags(new_pte, flags);
        rpte = __real_pte(__pte(old_pte), ptep, PTRS_PER_PTE);

        if (cpu_has_feature(CPU_FTR_NOEXECUTE) &&
            !cpu_has_feature(CPU_FTR_COHERENT_ICACHE))
                rflags = hash_page_do_lazy_icache(rflags, __pte(old_pte), trap);

        vpn  = hpt_vpn(ea, vsid, ssize);
        if (unlikely(old_pte & H_PAGE_HASHPTE)) {
                unsigned long gslot;

                /*
                 * There MIGHT be an HPTE for this pte
                 */
                gslot = pte_get_hash_gslot(vpn, shift, ssize, rpte, 0);
                if (mmu_hash_ops.hpte_updatepp(gslot, rflags, vpn, MMU_PAGE_64K,
                                               MMU_PAGE_64K, ssize,
                                               flags) == -1)
                        old_pte &= ~_PAGE_HPTEFLAGS;
        }

        if (likely(!(old_pte & H_PAGE_HASHPTE))) {

                pa = pte_pfn(__pte(old_pte)) << PAGE_SHIFT;
                hash = hpt_hash(vpn, shift, ssize);

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

                /* Insert into the hash table, primary slot */
                slot = mmu_hash_ops.hpte_insert(hpte_group, vpn, pa, rflags, 0,
                                                MMU_PAGE_64K, MMU_PAGE_64K,
                                                ssize);
                /*
                 * Primary is full, try the secondary
                 */
                if (unlikely(slot == -1)) {
                        hpte_group = (~hash & htab_hash_mask) * HPTES_PER_GROUP;
                        slot = mmu_hash_ops.hpte_insert(hpte_group, vpn, pa,
                                                        rflags,
                                                        HPTE_V_SECONDARY,
                                                        MMU_PAGE_64K,
                                                        MMU_PAGE_64K, ssize);
                        if (slot == -1) {
                                if (mftb() & 0x1)
                                        hpte_group = (hash & htab_hash_mask) *
                                                        HPTES_PER_GROUP;
                                mmu_hash_ops.hpte_remove(hpte_group);
                                /*
                                 * FIXME!! Should be try the group from which we removed ?
                                 */
                                goto repeat;
                        }
                }
                /*
                 * Hypervisor failure. Restore old pte and return -1
                 * similar to __hash_page_*
                 */
                if (unlikely(slot == -2)) {
                        *ptep = __pte(old_pte);
                        hash_failure_debug(ea, access, vsid, trap, ssize,
                                           MMU_PAGE_64K, MMU_PAGE_64K, old_pte);
                        return -1;
                }

                new_pte = (new_pte & ~_PAGE_HPTEFLAGS) | H_PAGE_HASHPTE;
                new_pte |= pte_set_hidx(ptep, rpte, 0, slot, PTRS_PER_PTE);
        }
        *ptep = __pte(new_pte & ~H_PAGE_BUSY);
        return 0;
}