linux/arch/powerpc/mm/hugetlbpage-hash64.c

/*
 * PPC64 Huge TLB Page Support for hash based MMUs (POWER4 and later)
 *
 * Copyright (C) 2003 David Gibson, IBM Corporation.
 *
 * Based on the IA-32 version:
 * Copyright (C) 2002, Rohit Seth <rohit.seth@intel.com>
 */

#include <linux/mm.h>
#include <linux/hugetlb.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
#include <asm/cacheflush.h>
#include <asm/machdep.h>

int __hash_page_huge(unsigned long ea, unsigned long access, unsigned long vsid,
		     pte_t *ptep, unsigned long trap, int local, int ssize,
		     unsigned int shift, unsigned int mmu_psize)
{
	unsigned long old_pte, new_pte;
	unsigned long va, rflags, pa, sz;
	long slot;

	BUG_ON(shift != mmu_psize_defs[mmu_psize].shift);

	/* Search the Linux page table for a match with va */
	va = hpt_va(ea, vsid, ssize);

	/* At this point, we have a pte (old_pte) which can be used to build
	 * or update an HPTE. There are 2 cases:
	 *
	 * 1. There is a valid (present) pte with no associated HPTE (this is
	 *	the most common case)
	 * 2. There is a valid (present) pte with an associated HPTE. The
	 *	current values of the pp bits in the HPTE prevent access
	 *	because we are doing software DIRTY bit management and the
	 *	page is currently not DIRTY.
	 */


	do {
		old_pte = pte_val(*ptep);
		/* If PTE busy, retry the access */
		if (unlikely(old_pte & _PAGE_BUSY))
			return 0;
		/* If PTE permissions don't match, take page fault */
		if (unlikely(access & ~old_pte))
			return 1;
		/* Try to lock the PTE, add ACCESSED and DIRTY if it was
		 * a write access */
		new_pte = old_pte | _PAGE_BUSY | _PAGE_ACCESSED;
		if (access & _PAGE_RW)
			new_pte |= _PAGE_DIRTY;
	} while(old_pte != __cmpxchg_u64((unsigned long *)ptep,
					 old_pte, new_pte));

	rflags = 0x2 | (!(new_pte & _PAGE_RW));
	/* _PAGE_EXEC -> HW_NO_EXEC since it's inverted */
	rflags |= ((new_pte & _PAGE_EXEC) ? 0 : HPTE_R_N);
	sz = ((1UL) << shift);
	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);

	/* Check if pte already has an hpte (case 2) */
	if (unlikely(old_pte & _PAGE_HASHPTE)) {
		/* There MIGHT be an HPTE for this pte */
		unsigned long hash, slot;

		hash = hpt_hash(va, shift, ssize);
		if (old_pte & _PAGE_F_SECOND)
			hash = ~hash;
		slot = (hash & htab_hash_mask) * HPTES_PER_GROUP;
		slot += (old_pte & _PAGE_F_GIX) >> 12;

		if (ppc_md.hpte_updatepp(slot, rflags, va, mmu_psize,
					 ssize, local) == -1)
			old_pte &= ~_PAGE_HPTEFLAGS;
	}

	if (likely(!(old_pte & _PAGE_HASHPTE))) {
		unsigned long hash = hpt_hash(va, shift, ssize);
		unsigned long hpte_group;

		pa = pte_pfn(__pte(old_pte)) << PAGE_SHIFT;

repeat:
		hpte_group = ((hash & htab_hash_mask) *
			      HPTES_PER_GROUP) & ~0x7UL;

		/* clear HPTE slot informations in new PTE */
#ifdef CONFIG_PPC_64K_PAGES
		new_pte = (new_pte & ~_PAGE_HPTEFLAGS) | _PAGE_HPTE_SUB0;
#else
		new_pte = (new_pte & ~_PAGE_HPTEFLAGS) | _PAGE_HASHPTE;
#endif
		/* Add in WIMG bits */
		rflags |= (new_pte & (_PAGE_WRITETHRU | _PAGE_NO_CACHE |
				      _PAGE_COHERENT | _PAGE_GUARDED));

		/* Insert into the hash table, primary slot */
		slot = ppc_md.hpte_insert(hpte_group, va, pa, rflags, 0,
					  mmu_psize, 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, va, pa, rflags,
						  HPTE_V_SECONDARY,
						  mmu_psize, 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 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_psize, old_pte);
			return -1;
		}

		new_pte |= (slot << 12) & (_PAGE_F_SECOND | _PAGE_F_GIX);
	}

	/*
	 * No need to use ldarx/stdcx here
	 */
	*ptep = __pte(new_pte & ~_PAGE_BUSY);
	return 0;
}