/*
 * 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>

#include "internal.h"

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 long rflags, pa;
        unsigned long old_pte, new_pte;
        unsigned long vpn, hash, slot;
        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;
                if (access & _PAGE_WRITE)
                        new_pte |= _PAGE_DIRTY;
        } while (!pte_xchg(ptep, __pte(old_pte), __pte(new_pte)));

        /*
         * PP bits. _PAGE_USER is already PP bit 0x2, so we only
         * need to add in 0x1 if it's a read-only user page
         */
        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)) {
                /*
                 * There MIGHT be an HPTE for this pte
                 */
                unsigned long gslot = pte_get_hash_gslot(vpn, shift, ssize,
                                                         rpte, 0);

                if (mmu_hash_ops.hpte_updatepp(gslot, rflags, vpn, MMU_PAGE_4K,
                                               MMU_PAGE_4K, 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_4K, MMU_PAGE_4K, 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_4K,
                                                        MMU_PAGE_4K, 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_4K, MMU_PAGE_4K, 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);

                if (stress_hpt())
                        hpt_do_stress(ea, hpte_group);
        }
        *ptep = __pte(new_pte & ~H_PAGE_BUSY);
        return 0;
}