1/*
  2 * PPC64 Huge TLB Page Support for hash based MMUs (POWER4 and later)
  3 *
  4 * Copyright (C) 2003 David Gibson, IBM Corporation.
  5 *
  6 * Based on the IA-32 version:
  7 * Copyright (C) 2002, Rohit Seth <rohit.seth@intel.com>
  8 */
  9
 10#include <linux/mm.h>
 11#include <linux/hugetlb.h>
 12#include <asm/pgtable.h>
 13#include <asm/pgalloc.h>
 14#include <asm/cacheflush.h>
 15#include <asm/machdep.h>
 16
 17extern long hpte_insert_repeating(unsigned long hash, unsigned long vpn,
 18				  unsigned long pa, unsigned long rlags,
 19				  unsigned long vflags, int psize, int ssize);
 20
 21int __hash_page_huge(unsigned long ea, unsigned long access, unsigned long vsid,
 22		     pte_t *ptep, unsigned long trap, unsigned long flags,
 23		     int ssize, unsigned int shift, unsigned int mmu_psize)
 24{
 25	unsigned long vpn;
 26	unsigned long old_pte, new_pte;
 27	unsigned long rflags, pa, sz;
 28	long slot;
 29
 30	BUG_ON(shift != mmu_psize_defs[mmu_psize].shift);
 31
 32	/* Search the Linux page table for a match with va */
 33	vpn = hpt_vpn(ea, vsid, ssize);
 34
 35	/* At this point, we have a pte (old_pte) which can be used to build
 36	 * or update an HPTE. There are 2 cases:
 37	 *
 38	 * 1. There is a valid (present) pte with no associated HPTE (this is
 39	 *	the most common case)
 40	 * 2. There is a valid (present) pte with an associated HPTE. The
 41	 *	current values of the pp bits in the HPTE prevent access
 42	 *	because we are doing software DIRTY bit management and the
 43	 *	page is currently not DIRTY.
 44	 */
 45
 46
 47	do {
 48		old_pte = pte_val(*ptep);
 49		/* If PTE busy, retry the access */
 50		if (unlikely(old_pte & H_PAGE_BUSY))
 51			return 0;
 52		/* If PTE permissions don't match, take page fault */
 53		if (unlikely(!check_pte_access(access, old_pte)))
 54			return 1;
 55
 56		/* Try to lock the PTE, add ACCESSED and DIRTY if it was
 57		 * a write access */
 58		new_pte = old_pte | H_PAGE_BUSY | _PAGE_ACCESSED;
 59		if (access & _PAGE_WRITE)
 60			new_pte |= _PAGE_DIRTY;
 61	} while(!pte_xchg(ptep, __pte(old_pte), __pte(new_pte)));
 62
 63	rflags = htab_convert_pte_flags(new_pte);
 64
 65	sz = ((1UL) << shift);
 66	if (!cpu_has_feature(CPU_FTR_COHERENT_ICACHE))
 67		/* No CPU has hugepages but lacks no execute, so we
 68		 * don't need to worry about that case */
 69		rflags = hash_page_do_lazy_icache(rflags, __pte(old_pte), trap);
 70
 71	/* Check if pte already has an hpte (case 2) */
 72	if (unlikely(old_pte & H_PAGE_HASHPTE)) {
 73		/* There MIGHT be an HPTE for this pte */
 74		unsigned long hash, slot;
 75
 76		hash = hpt_hash(vpn, shift, ssize);
 77		if (old_pte & H_PAGE_F_SECOND)
 78			hash = ~hash;
 79		slot = (hash & htab_hash_mask) * HPTES_PER_GROUP;
 80		slot += (old_pte & H_PAGE_F_GIX) >> H_PAGE_F_GIX_SHIFT;
 81
 82		if (mmu_hash_ops.hpte_updatepp(slot, rflags, vpn, mmu_psize,
 83					       mmu_psize, ssize, flags) == -1)
 84			old_pte &= ~_PAGE_HPTEFLAGS;
 85	}
 86
 87	if (likely(!(old_pte & H_PAGE_HASHPTE))) {
 88		unsigned long hash = hpt_hash(vpn, shift, ssize);
 89
 90		pa = pte_pfn(__pte(old_pte)) << PAGE_SHIFT;
 91
 92		/* clear HPTE slot informations in new PTE */
 93		new_pte = (new_pte & ~_PAGE_HPTEFLAGS) | H_PAGE_HASHPTE;
 94
 95		slot = hpte_insert_repeating(hash, vpn, pa, rflags, 0,
 96					     mmu_psize, ssize);
 97
 98		/*
 99		 * Hypervisor failure. Restore old pte and return -1
100		 * similar to __hash_page_*
101		 */
102		if (unlikely(slot == -2)) {
103			*ptep = __pte(old_pte);
104			hash_failure_debug(ea, access, vsid, trap, ssize,
105					   mmu_psize, mmu_psize, old_pte);
106			return -1;
107		}
108
109		new_pte |= (slot << H_PAGE_F_GIX_SHIFT) &
110			(H_PAGE_F_SECOND | H_PAGE_F_GIX);
111	}
112
113	/*
114	 * No need to use ldarx/stdcx here
115	 */
116	*ptep = __pte(new_pte & ~H_PAGE_BUSY);
117	return 0;
118}
119
120#if defined(CONFIG_PPC_64K_PAGES) && defined(CONFIG_DEBUG_VM)
121/*
122 * This enables us to catch the wrong page directory format
123 * Moved here so that we can use WARN() in the call.
124 */
125int hugepd_ok(hugepd_t hpd)
126{
127	bool is_hugepd;
128	unsigned long hpdval;
129
130	hpdval = hpd_val(hpd);
131
132	/*
133	 * We should not find this format in page directory, warn otherwise.
134	 */
135	is_hugepd = (((hpdval & 0x3) == 0x0) && ((hpdval & HUGEPD_SHIFT_MASK) != 0));
136	WARN(is_hugepd, "Found wrong page directory format\n");
137	return 0;
138}
139#endif