/*
 * Copyright IBM Corporation, 2013
 * 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 2.1 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.
 *
 */

/*
 * PPC64 THP Support for hash based MMUs
 */
#include <linux/mm.h>
#include <asm/machdep.h>

int __hash_page_thp(unsigned long ea, unsigned long access, unsigned long vsid,
                    pmd_t *pmdp, unsigned long trap, unsigned long flags,
                    int ssize, unsigned int psize)
{
        unsigned int index, valid;
        unsigned char *hpte_slot_array;
        unsigned long rflags, pa, hidx;
        unsigned long old_pmd, new_pmd;
        int ret, lpsize = MMU_PAGE_16M;
        unsigned long vpn, hash, shift, slot;

        /*
         * atomically mark the linux large page PMD busy and dirty
         */
        do {
                pmd_t pmd = READ_ONCE(*pmdp);

                old_pmd = pmd_val(pmd);
                /* If PMD busy, retry the access */
                if (unlikely(old_pmd & H_PAGE_BUSY))
                        return 0;
                /* If PMD permissions don't match, take page fault */
                if (unlikely(!check_pte_access(access, old_pmd)))
                        return 1;
                /*
                 * Try to lock the PTE, add ACCESSED and DIRTY if it was
                 * a write access
                 */
                new_pmd = old_pmd | H_PAGE_BUSY | _PAGE_ACCESSED;
                if (access & _PAGE_WRITE)
                        new_pmd |= _PAGE_DIRTY;
        } while (!pmd_xchg(pmdp, __pmd(old_pmd), __pmd(new_pmd)));

        /*
         * Make sure this is thp or devmap entry
         */
        if (!(old_pmd & H_PAGE_THP_HUGE))
                return 0;

        rflags = htab_convert_pte_flags(new_pmd, flags);

        /*
         * THPs are only supported on platforms that can do mixed page size
         * segments (MPSS) and all such platforms have coherent icache. Hence we
         * don't need to do lazy icache flush (hash_page_do_lazy_icache()) on
         * noexecute fault.
         */

        /*
         * Find the slot index details for this ea, using base page size.
         */
        shift = mmu_psize_defs[psize].shift;
        index = (ea & ~HPAGE_PMD_MASK) >> shift;
        BUG_ON(index >= PTE_FRAG_SIZE);

        vpn = hpt_vpn(ea, vsid, ssize);
        hpte_slot_array = get_hpte_slot_array(pmdp);
        if (psize == MMU_PAGE_4K) {
                /*
                 * invalidate the old hpte entry if we have that mapped via 64K
                 * base page size. This is because demote_segment won't flush
                 * hash page table entries.
                 */
                if ((old_pmd & H_PAGE_HASHPTE) && !(old_pmd & H_PAGE_COMBO)) {
                        flush_hash_hugepage(vsid, ea, pmdp, MMU_PAGE_64K,
                                            ssize, flags);
                        /*
                         * With THP, we also clear the slot information with
                         * respect to all the 64K hash pte mapping the 16MB
                         * page. They are all invalid now. This make sure we
                         * don't find the slot valid when we fault with 4k
                         * base page size.
                         *
                         */
                        memset(hpte_slot_array, 0, PTE_FRAG_SIZE);
                }
        }

        valid = hpte_valid(hpte_slot_array, index);
        if (valid) {
                /* update the hpte bits */
                hash = hpt_hash(vpn, shift, ssize);
                hidx =  hpte_hash_index(hpte_slot_array, index);
                if (hidx & _PTEIDX_SECONDARY)
                        hash = ~hash;
                slot = (hash & htab_hash_mask) * HPTES_PER_GROUP;
                slot += hidx & _PTEIDX_GROUP_IX;

                ret = mmu_hash_ops.hpte_updatepp(slot, rflags, vpn,
                                                 psize, lpsize, ssize, flags);
                /*
                 * We failed to update, try to insert a new entry.
                 */
                if (ret == -1) {
                        /*
                         * large pte is marked busy, so we can be sure
                         * nobody is looking at hpte_slot_array. hence we can
                         * safely update this here.
                         */
                        valid = 0;
                        hpte_slot_array[index] = 0;
                }
        }

        if (!valid) {
                unsigned long hpte_group;

                hash = hpt_hash(vpn, shift, ssize);
                /* insert new entry */
                pa = pmd_pfn(__pmd(old_pmd)) << PAGE_SHIFT;
                new_pmd |= H_PAGE_HASHPTE;

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,
                                                psize, lpsize, 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,
                                                        psize, lpsize, ssize);
                        if (slot == -1) {
                                if (mftb() & 0x1)
                                        hpte_group = (hash & htab_hash_mask) *
                                                        HPTES_PER_GROUP;

                                mmu_hash_ops.hpte_remove(hpte_group);
                                goto repeat;
                        }
                }
                /*
                 * Hypervisor failure. Restore old pmd and return -1
                 * similar to __hash_page_*
                 */
                if (unlikely(slot == -2)) {
                        *pmdp = __pmd(old_pmd);
                        hash_failure_debug(ea, access, vsid, trap, ssize,
                                           psize, lpsize, old_pmd);
                        return -1;
                }
                /*
                 * large pte is marked busy, so we can be sure
                 * nobody is looking at hpte_slot_array. hence we can
                 * safely update this here.
                 */
                mark_hpte_slot_valid(hpte_slot_array, index, slot);
        }
        /*
         * Mark the pte with H_PAGE_COMBO, if we are trying to hash it with
         * base page size 4k.
         */
        if (psize == MMU_PAGE_4K)
                new_pmd |= H_PAGE_COMBO;
        /*
         * The hpte valid is stored in the pgtable whose address is in the
         * second half of the PMD. Order this against clearing of the busy bit in
         * huge pmd.
         */
        smp_wmb();
        *pmdp = __pmd(new_pmd & ~H_PAGE_BUSY);
        return 0;
}