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 & _PAGE_BUSY))
 51			return 0;
 52		/* If PTE permissions don't match, take page fault */
 53		if (unlikely(access & ~old_pte))
 54			return 1;
 55		/* Try to lock the PTE, add ACCESSED and DIRTY if it was
 56		 * a write access */
 57		new_pte = old_pte | _PAGE_BUSY | _PAGE_ACCESSED;
 58		if (access & _PAGE_RW)
 59			new_pte |= _PAGE_DIRTY;
 60	} while(old_pte != __cmpxchg_u64((unsigned long *)ptep,
 61					 old_pte, new_pte));
 62	rflags = htab_convert_pte_flags(new_pte);
 63
 64	sz = ((1UL) << shift);
 65	if (!cpu_has_feature(CPU_FTR_COHERENT_ICACHE))
 66		/* No CPU has hugepages but lacks no execute, so we
 67		 * don't need to worry about that case */
 68		rflags = hash_page_do_lazy_icache(rflags, __pte(old_pte), trap);
 69
 70	/* Check if pte already has an hpte (case 2) */
 71	if (unlikely(old_pte & _PAGE_HASHPTE)) {
 72		/* There MIGHT be an HPTE for this pte */
 73		unsigned long hash, slot;
 74
 75		hash = hpt_hash(vpn, shift, ssize);
 76		if (old_pte & _PAGE_F_SECOND)
 77			hash = ~hash;
 78		slot = (hash & htab_hash_mask) * HPTES_PER_GROUP;
 79		slot += (old_pte & _PAGE_F_GIX) >> _PAGE_F_GIX_SHIFT;
 80
 81		if (ppc_md.hpte_updatepp(slot, rflags, vpn, mmu_psize,
 82					 mmu_psize, ssize, flags) == -1)
 83			old_pte &= ~_PAGE_HPTEFLAGS;
 84	}
 85
 86	if (likely(!(old_pte & _PAGE_HASHPTE))) {
 87		unsigned long hash = hpt_hash(vpn, shift, ssize);
 88
 89		pa = pte_pfn(__pte(old_pte)) << PAGE_SHIFT;
 90
 91		/* clear HPTE slot informations in new PTE */
 92		new_pte = (new_pte & ~_PAGE_HPTEFLAGS) | _PAGE_HASHPTE;
 93
 94		slot = hpte_insert_repeating(hash, vpn, pa, rflags, 0,
 95					     mmu_psize, ssize);
 96
 97		/*
 98		 * Hypervisor failure. Restore old pte and return -1
 99		 * similar to __hash_page_*
100		 */
101		if (unlikely(slot == -2)) {
102			*ptep = __pte(old_pte);
103			hash_failure_debug(ea, access, vsid, trap, ssize,
104					   mmu_psize, mmu_psize, old_pte);
105			return -1;
106		}
107
108		new_pte |= (slot << _PAGE_F_GIX_SHIFT) &
109			(_PAGE_F_SECOND | _PAGE_F_GIX);
110	}
111
112	/*
113	 * No need to use ldarx/stdcx here
114	 */
115	*ptep = __pte(new_pte & ~_PAGE_BUSY);
116	return 0;
117}
118
119#if defined(CONFIG_PPC_64K_PAGES) && defined(CONFIG_DEBUG_VM)
120/*
121 * This enables us to catch the wrong page directory format
122 * Moved here so that we can use WARN() in the call.
123 */
124int hugepd_ok(hugepd_t hpd)
125{
126	bool is_hugepd;
127
128	/*
129	 * We should not find this format in page directory, warn otherwise.
130	 */
131	is_hugepd = (((hpd.pd & 0x3) == 0x0) && ((hpd.pd & HUGEPD_SHIFT_MASK) != 0));
132	WARN(is_hugepd, "Found wrong page directory format\n");
133	return 0;
134}
135#endif