/*
   * Copyright IBM Corporation, 2013
   * Author Aneesh Kumar K.V <aneesh.kumar@linux.vnet.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>
  
  static void invalidate_old_hpte(unsigned long vsid, unsigned long addr,
  				pmd_t *pmdp, unsigned int psize, int ssize)
  {
  	int i, max_hpte_count, valid;
  	unsigned long s_addr;
  	unsigned char *hpte_slot_array;
  	unsigned long hidx, shift, vpn, hash, slot;
  
  	s_addr = addr & HPAGE_PMD_MASK;
  	hpte_slot_array = get_hpte_slot_array(pmdp);
  	/*
  	 * IF we try to do a HUGE PTE update after a withdraw is done.
  	 * we will find the below NULL. This happens when we do
  	 * split_huge_page_pmd
  	 */
  	if (!hpte_slot_array)
  		return;
  
  	if (ppc_md.hugepage_invalidate)
  		return ppc_md.hugepage_invalidate(vsid, s_addr, hpte_slot_array,
  						  psize, ssize);
  	/*
  	 * No bluk hpte removal support, invalidate each entry
  	 */
  	shift = mmu_psize_defs[psize].shift;
  	max_hpte_count = HPAGE_PMD_SIZE >> shift;
  	for (i = 0; i < max_hpte_count; i++) {
  		/*
  		 * 8 bits per each hpte entries
  		 * 000| [ secondary group (one bit) | hidx (3 bits) | valid bit]
  		 */
  		valid = hpte_valid(hpte_slot_array, i);
  		if (!valid)
  			continue;
  		hidx =  hpte_hash_index(hpte_slot_array, i);
  
  		/* get the vpn */
  		addr = s_addr + (i * (1ul << shift));
  		vpn = hpt_vpn(addr, vsid, ssize);
  		hash = hpt_hash(vpn, shift, ssize);
  		if (hidx & _PTEIDX_SECONDARY)
  			hash = ~hash;
  
  		slot = (hash & htab_hash_mask) * HPTES_PER_GROUP;
  		slot += hidx & _PTEIDX_GROUP_IX;
  		ppc_md.hpte_invalidate(slot, vpn, psize,
  				       MMU_PAGE_16M, ssize, 0);
  	}
  }
  
  
  int __hash_page_thp(unsigned long ea, unsigned long access, unsigned long vsid,
  		    pmd_t *pmdp, unsigned long trap, int local, 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 = ACCESS_ONCE(*pmdp);
  
  		old_pmd = pmd_val(pmd);
  		/* If PMD busy, retry the access */
  		if (unlikely(old_pmd & _PAGE_BUSY))
  			return 0;
  		/* If PMD is trans splitting retry the access */
  		if (unlikely(old_pmd & _PAGE_SPLITTING))
  			return 0;
  		/* If PMD permissions don't match, take page fault */
  		if (unlikely(access & ~old_pmd))
  			return 1;
  		/*
  		 * Try to lock the PTE, add ACCESSED and DIRTY if it was
  		 * a write access
  		 */
  		new_pmd = old_pmd | _PAGE_BUSY | _PAGE_ACCESSED;
  		if (access & _PAGE_RW)
  			new_pmd |= _PAGE_DIRTY;
  	} while (old_pmd != __cmpxchg_u64((unsigned long *)pmdp,
  					  old_pmd, new_pmd));
  	/*
  	 * 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 = new_pmd & _PAGE_USER;
  	if ((new_pmd & _PAGE_USER) && !((new_pmd & _PAGE_RW) &&
  					   (new_pmd & _PAGE_DIRTY)))
  		rflags |= 0x1;
  	/*
  	 * _PAGE_EXEC -> HW_NO_EXEC since it's inverted
  	 */
  	rflags |= ((new_pmd & _PAGE_EXEC) ? 0 : HPTE_R_N);
  
  #if 0
  	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_page_do_lazy_icache(rflags, __pte(old_pte), trap);
  	}
  #endif
  	/*
  	 * 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 >= 4096);
  
  	vpn = hpt_vpn(ea, vsid, ssize);
  	hash = hpt_hash(vpn, shift, 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 & _PAGE_HASHPTE) && !(old_pmd & _PAGE_COMBO))
  			invalidate_old_hpte(vsid, ea, pmdp, MMU_PAGE_64K, ssize);
  	}
  
  	valid = hpte_valid(hpte_slot_array, index);
  	if (valid) {
  		/* update the hpte bits */
  		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 = ppc_md.hpte_updatepp(slot, rflags, vpn,
  					   psize, lpsize, ssize, local);
  		/*
  		 * 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;
  
  		/* insert new entry */
  		pa = pmd_pfn(__pmd(old_pmd)) << PAGE_SHIFT;
  		new_pmd |= _PAGE_HASHPTE;
  
  		/* Add in WIMG bits */
  		rflags |= (new_pmd & (_PAGE_WRITETHRU | _PAGE_NO_CACHE |
  				      _PAGE_GUARDED));
  		/*
  		 * enable the memory coherence always
  		 */
  		rflags |= HPTE_R_M;
  repeat:
  		hpte_group = ((hash & htab_hash_mask) * HPTES_PER_GROUP) & ~0x7UL;
  
  		/* Insert into the hash table, primary slot */
  		slot = ppc_md.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) & ~0x7UL;
  			slot = ppc_md.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) & ~0x7UL;
  
  				ppc_md.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 _PAGE_COMBO, if we are trying to hash it with
  	 * base page size 4k.
  	 */
  	if (psize == MMU_PAGE_4K)
  		new_pmd |= _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 & ~_PAGE_BUSY);
  	return 0;
  }