[ARM] Support register switch in nommu mode

[linux-2.6/verdex.git] / arch / powerpc / mm / hugetlbpage.c

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

#include <linux/init.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/hugetlb.h>
#include <linux/pagemap.h>
#include <linux/smp_lock.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/sysctl.h>
#include <asm/mman.h>
#include <asm/pgalloc.h>
#include <asm/tlb.h>
#include <asm/tlbflush.h>
#include <asm/mmu_context.h>
#include <asm/machdep.h>
#include <asm/cputable.h>
#include <asm/tlb.h>

#include <linux/sysctl.h>

#define NUM_LOW_AREAS   (0x100000000UL >> SID_SHIFT)
#define NUM_HIGH_AREAS  (PGTABLE_RANGE >> HTLB_AREA_SHIFT)

/* Modelled after find_linux_pte() */
pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr)
{
        pgd_t *pg;
        pud_t *pu;
        pmd_t *pm;
        pte_t *pt;

        BUG_ON(! in_hugepage_area(mm->context, addr));

        addr &= HPAGE_MASK;

        pg = pgd_offset(mm, addr);
        if (!pgd_none(*pg)) {
                pu = pud_offset(pg, addr);
                if (!pud_none(*pu)) {
                        pm = pmd_offset(pu, addr);
#ifdef CONFIG_PPC_64K_PAGES
                        /* Currently, we use the normal PTE offset within full
                         * size PTE pages, thus our huge PTEs are scattered in
                         * the PTE page and we do waste some. We may change
                         * that in the future, but the current mecanism keeps
                         * things much simpler
                         */
                        if (!pmd_none(*pm)) {
                                /* Note: pte_offset_* are all equivalent on
                                 * ppc64 as we don't have HIGHMEM
                                 */
                                pt = pte_offset_kernel(pm, addr);
                                return pt;
                        }
#else /* CONFIG_PPC_64K_PAGES */
                        /* On 4k pages, we put huge PTEs in the PMD page */
                        pt = (pte_t *)pm;
                        return pt;
#endif /* CONFIG_PPC_64K_PAGES */
                }
        }

        return NULL;
}

pte_t *huge_pte_alloc(struct mm_struct *mm, unsigned long addr)
{
        pgd_t *pg;
        pud_t *pu;
        pmd_t *pm;
        pte_t *pt;

        BUG_ON(! in_hugepage_area(mm->context, addr));

        addr &= HPAGE_MASK;

        pg = pgd_offset(mm, addr);
        pu = pud_alloc(mm, pg, addr);

        if (pu) {
                pm = pmd_alloc(mm, pu, addr);
                if (pm) {
#ifdef CONFIG_PPC_64K_PAGES
                        /* See comment in huge_pte_offset. Note that if we ever
                         * want to put the page size in the PMD, we would have
                         * to open code our own pte_alloc* function in order
                         * to populate and set the size atomically
                         */
                        pt = pte_alloc_map(mm, pm, addr);
#else /* CONFIG_PPC_64K_PAGES */
                        pt = (pte_t *)pm;
#endif /* CONFIG_PPC_64K_PAGES */
                        return pt;
                }
        }

        return NULL;
}

void set_huge_pte_at(struct mm_struct *mm, unsigned long addr,
                     pte_t *ptep, pte_t pte)
{
        if (pte_present(*ptep)) {
                /* We open-code pte_clear because we need to pass the right
                 * argument to hpte_update (huge / !huge)
                 */
                unsigned long old = pte_update(ptep, ~0UL);
                if (old & _PAGE_HASHPTE)
                        hpte_update(mm, addr & HPAGE_MASK, ptep, old, 1);
                flush_tlb_pending();
        }
        *ptep = __pte(pte_val(pte) & ~_PAGE_HPTEFLAGS);
}

pte_t huge_ptep_get_and_clear(struct mm_struct *mm, unsigned long addr,
                              pte_t *ptep)
{
        unsigned long old = pte_update(ptep, ~0UL);

        if (old & _PAGE_HASHPTE)
                hpte_update(mm, addr & HPAGE_MASK, ptep, old, 1);
        *ptep = __pte(0);

        return __pte(old);
}

/*
 * This function checks for proper alignment of input addr and len parameters.
 */
int is_aligned_hugepage_range(unsigned long addr, unsigned long len)
{
        if (len & ~HPAGE_MASK)
                return -EINVAL;
        if (addr & ~HPAGE_MASK)
                return -EINVAL;
        if (! (within_hugepage_low_range(addr, len)
               || within_hugepage_high_range(addr, len)) )
                return -EINVAL;
        return 0;
}

struct slb_flush_info {
        struct mm_struct *mm;
        u16 newareas;
};

static void flush_low_segments(void *parm)
{
        struct slb_flush_info *fi = parm;
        unsigned long i;

        BUILD_BUG_ON((sizeof(fi->newareas)*8) != NUM_LOW_AREAS);

        if (current->active_mm != fi->mm)
                return;

        /* Only need to do anything if this CPU is working in the same
         * mm as the one which has changed */

        /* update the paca copy of the context struct */
        get_paca()->context = current->active_mm->context;

        asm volatile("isync" : : : "memory");
        for (i = 0; i < NUM_LOW_AREAS; i++) {
                if (! (fi->newareas & (1U << i)))
                        continue;
                asm volatile("slbie %0"
                             : : "r" ((i << SID_SHIFT) | SLBIE_C));
        }
        asm volatile("isync" : : : "memory");
}

static void flush_high_segments(void *parm)
{
        struct slb_flush_info *fi = parm;
        unsigned long i, j;


        BUILD_BUG_ON((sizeof(fi->newareas)*8) != NUM_HIGH_AREAS);

        if (current->active_mm != fi->mm)
                return;

        /* Only need to do anything if this CPU is working in the same
         * mm as the one which has changed */

        /* update the paca copy of the context struct */
        get_paca()->context = current->active_mm->context;

        asm volatile("isync" : : : "memory");
        for (i = 0; i < NUM_HIGH_AREAS; i++) {
                if (! (fi->newareas & (1U << i)))
                        continue;
                for (j = 0; j < (1UL << (HTLB_AREA_SHIFT-SID_SHIFT)); j++)
                        asm volatile("slbie %0"
                                     :: "r" (((i << HTLB_AREA_SHIFT)
                                              + (j << SID_SHIFT)) | SLBIE_C));
        }
        asm volatile("isync" : : : "memory");
}

static int prepare_low_area_for_htlb(struct mm_struct *mm, unsigned long area)
{
        unsigned long start = area << SID_SHIFT;
        unsigned long end = (area+1) << SID_SHIFT;
        struct vm_area_struct *vma;

        BUG_ON(area >= NUM_LOW_AREAS);

        /* Check no VMAs are in the region */
        vma = find_vma(mm, start);
        if (vma && (vma->vm_start < end))
                return -EBUSY;

        return 0;
}

static int prepare_high_area_for_htlb(struct mm_struct *mm, unsigned long area)
{
        unsigned long start = area << HTLB_AREA_SHIFT;
        unsigned long end = (area+1) << HTLB_AREA_SHIFT;
        struct vm_area_struct *vma;

        BUG_ON(area >= NUM_HIGH_AREAS);

        /* Hack, so that each addresses is controlled by exactly one
         * of the high or low area bitmaps, the first high area starts
         * at 4GB, not 0 */
        if (start == 0)
                start = 0x100000000UL;

        /* Check no VMAs are in the region */
        vma = find_vma(mm, start);
        if (vma && (vma->vm_start < end))
                return -EBUSY;

        return 0;
}

static int open_low_hpage_areas(struct mm_struct *mm, u16 newareas)
{
        unsigned long i;
        struct slb_flush_info fi;

        BUILD_BUG_ON((sizeof(newareas)*8) != NUM_LOW_AREAS);
        BUILD_BUG_ON((sizeof(mm->context.low_htlb_areas)*8) != NUM_LOW_AREAS);

        newareas &= ~(mm->context.low_htlb_areas);
        if (! newareas)
                return 0; /* The segments we want are already open */

        for (i = 0; i < NUM_LOW_AREAS; i++)
                if ((1 << i) & newareas)
                        if (prepare_low_area_for_htlb(mm, i) != 0)
                                return -EBUSY;

        mm->context.low_htlb_areas |= newareas;

        /* the context change must make it to memory before the flush,
         * so that further SLB misses do the right thing. */
        mb();

        fi.mm = mm;
        fi.newareas = newareas;
        on_each_cpu(flush_low_segments, &fi, 0, 1);

        return 0;
}

static int open_high_hpage_areas(struct mm_struct *mm, u16 newareas)
{
        struct slb_flush_info fi;
        unsigned long i;

        BUILD_BUG_ON((sizeof(newareas)*8) != NUM_HIGH_AREAS);
        BUILD_BUG_ON((sizeof(mm->context.high_htlb_areas)*8)
                     != NUM_HIGH_AREAS);

        newareas &= ~(mm->context.high_htlb_areas);
        if (! newareas)
                return 0; /* The areas we want are already open */

        for (i = 0; i < NUM_HIGH_AREAS; i++)
                if ((1 << i) & newareas)
                        if (prepare_high_area_for_htlb(mm, i) != 0)
                                return -EBUSY;

        mm->context.high_htlb_areas |= newareas;

        /* update the paca copy of the context struct */
        get_paca()->context = mm->context;

        /* the context change must make it to memory before the flush,
         * so that further SLB misses do the right thing. */
        mb();

        fi.mm = mm;
        fi.newareas = newareas;
        on_each_cpu(flush_high_segments, &fi, 0, 1);

        return 0;
}

int prepare_hugepage_range(unsigned long addr, unsigned long len)
{
        int err = 0;

        if ( (addr+len) < addr )
                return -EINVAL;

        if (addr < 0x100000000UL)
                err = open_low_hpage_areas(current->mm,
                                          LOW_ESID_MASK(addr, len));
        if ((addr + len) > 0x100000000UL)
                err = open_high_hpage_areas(current->mm,
                                            HTLB_AREA_MASK(addr, len));
        if (err) {
                printk(KERN_DEBUG "prepare_hugepage_range(%lx, %lx)"
                       " failed (lowmask: 0x%04hx, highmask: 0x%04hx)\n",
                       addr, len,
                       LOW_ESID_MASK(addr, len), HTLB_AREA_MASK(addr, len));
                return err;
        }

        return 0;
}

struct page *
follow_huge_addr(struct mm_struct *mm, unsigned long address, int write)
{
        pte_t *ptep;
        struct page *page;

        if (! in_hugepage_area(mm->context, address))
                return ERR_PTR(-EINVAL);

        ptep = huge_pte_offset(mm, address);
        page = pte_page(*ptep);
        if (page)
                page += (address % HPAGE_SIZE) / PAGE_SIZE;

        return page;
}

int pmd_huge(pmd_t pmd)
{
        return 0;
}

struct page *
follow_huge_pmd(struct mm_struct *mm, unsigned long address,
                pmd_t *pmd, int write)
{
        BUG();
        return NULL;
}

/* Because we have an exclusive hugepage region which lies within the
 * normal user address space, we have to take special measures to make
 * non-huge mmap()s evade the hugepage reserved regions. */
unsigned long arch_get_unmapped_area(struct file *filp, unsigned long addr,
                                     unsigned long len, unsigned long pgoff,
                                     unsigned long flags)
{
        struct mm_struct *mm = current->mm;
        struct vm_area_struct *vma;
        unsigned long start_addr;

        if (len > TASK_SIZE)
                return -ENOMEM;

        if (addr) {
                addr = PAGE_ALIGN(addr);
                vma = find_vma(mm, addr);
                if (((TASK_SIZE - len) >= addr)
                    && (!vma || (addr+len) <= vma->vm_start)
                    && !is_hugepage_only_range(mm, addr,len))
                        return addr;
        }
        if (len > mm->cached_hole_size) {
                start_addr = addr = mm->free_area_cache;
        } else {
                start_addr = addr = TASK_UNMAPPED_BASE;
                mm->cached_hole_size = 0;
        }

full_search:
        vma = find_vma(mm, addr);
        while (TASK_SIZE - len >= addr) {
                BUG_ON(vma && (addr >= vma->vm_end));

                if (touches_hugepage_low_range(mm, addr, len)) {
                        addr = ALIGN(addr+1, 1<<SID_SHIFT);
                        vma = find_vma(mm, addr);
                        continue;
                }
                if (touches_hugepage_high_range(mm, addr, len)) {
                        addr = ALIGN(addr+1, 1UL<<HTLB_AREA_SHIFT);
                        vma = find_vma(mm, addr);
                        continue;
                }
                if (!vma || addr + len <= vma->vm_start) {
                        /*
                         * Remember the place where we stopped the search:
                         */
                        mm->free_area_cache = addr + len;
                        return addr;
                }
                if (addr + mm->cached_hole_size < vma->vm_start)
                        mm->cached_hole_size = vma->vm_start - addr;
                addr = vma->vm_end;
                vma = vma->vm_next;
        }

        /* Make sure we didn't miss any holes */
        if (start_addr != TASK_UNMAPPED_BASE) {
                start_addr = addr = TASK_UNMAPPED_BASE;
                mm->cached_hole_size = 0;
                goto full_search;
        }
        return -ENOMEM;
}

/*
 * This mmap-allocator allocates new areas top-down from below the
 * stack's low limit (the base):
 *
 * Because we have an exclusive hugepage region which lies within the
 * normal user address space, we have to take special measures to make
 * non-huge mmap()s evade the hugepage reserved regions.
 */
unsigned long
arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
                          const unsigned long len, const unsigned long pgoff,
                          const unsigned long flags)
{
        struct vm_area_struct *vma, *prev_vma;
        struct mm_struct *mm = current->mm;
        unsigned long base = mm->mmap_base, addr = addr0;
        unsigned long largest_hole = mm->cached_hole_size;
        int first_time = 1;

        /* requested length too big for entire address space */
        if (len > TASK_SIZE)
                return -ENOMEM;

        /* dont allow allocations above current base */
        if (mm->free_area_cache > base)
                mm->free_area_cache = base;

        /* requesting a specific address */
        if (addr) {
                addr = PAGE_ALIGN(addr);
                vma = find_vma(mm, addr);
                if (TASK_SIZE - len >= addr &&
                                (!vma || addr + len <= vma->vm_start)
                                && !is_hugepage_only_range(mm, addr,len))
                        return addr;
        }

        if (len <= largest_hole) {
                largest_hole = 0;
                mm->free_area_cache = base;
        }
try_again:
        /* make sure it can fit in the remaining address space */
        if (mm->free_area_cache < len)
                goto fail;

        /* either no address requested or cant fit in requested address hole */
        addr = (mm->free_area_cache - len) & PAGE_MASK;
        do {
hugepage_recheck:
                if (touches_hugepage_low_range(mm, addr, len)) {
                        addr = (addr & ((~0) << SID_SHIFT)) - len;
                        goto hugepage_recheck;
                } else if (touches_hugepage_high_range(mm, addr, len)) {
                        addr = (addr & ((~0UL) << HTLB_AREA_SHIFT)) - len;
                        goto hugepage_recheck;
                }

                /*
                 * Lookup failure means no vma is above this address,
                 * i.e. return with success:
                 */
                if (!(vma = find_vma_prev(mm, addr, &prev_vma)))
                        return addr;

                /*
                 * new region fits between prev_vma->vm_end and
                 * vma->vm_start, use it:
                 */
                if (addr+len <= vma->vm_start &&
                          (!prev_vma || (addr >= prev_vma->vm_end))) {
                        /* remember the address as a hint for next time */
                        mm->cached_hole_size = largest_hole;
                        return (mm->free_area_cache = addr);
                } else {
                        /* pull free_area_cache down to the first hole */
                        if (mm->free_area_cache == vma->vm_end) {
                                mm->free_area_cache = vma->vm_start;
                                mm->cached_hole_size = largest_hole;
                        }
                }

                /* remember the largest hole we saw so far */
                if (addr + largest_hole < vma->vm_start)
                        largest_hole = vma->vm_start - addr;

                /* try just below the current vma->vm_start */
                addr = vma->vm_start-len;
        } while (len <= vma->vm_start);

fail:
        /*
         * if hint left us with no space for the requested
         * mapping then try again:
         */
        if (first_time) {
                mm->free_area_cache = base;
                largest_hole = 0;
                first_time = 0;
                goto try_again;
        }
        /*
         * A failed mmap() very likely causes application failure,
         * so fall back to the bottom-up function here. This scenario
         * can happen with large stack limits and large mmap()
         * allocations.
         */
        mm->free_area_cache = TASK_UNMAPPED_BASE;
        mm->cached_hole_size = ~0UL;
        addr = arch_get_unmapped_area(filp, addr0, len, pgoff, flags);
        /*
         * Restore the topdown base:
         */
        mm->free_area_cache = base;
        mm->cached_hole_size = ~0UL;

        return addr;
}

static int htlb_check_hinted_area(unsigned long addr, unsigned long len)
{
        struct vm_area_struct *vma;

        vma = find_vma(current->mm, addr);
        if (!vma || ((addr + len) <= vma->vm_start))
                return 0;

        return -ENOMEM;
}

static unsigned long htlb_get_low_area(unsigned long len, u16 segmask)
{
        unsigned long addr = 0;
        struct vm_area_struct *vma;

        vma = find_vma(current->mm, addr);
        while (addr + len <= 0x100000000UL) {
                BUG_ON(vma && (addr >= vma->vm_end)); /* invariant */

                if (! __within_hugepage_low_range(addr, len, segmask)) {
                        addr = ALIGN(addr+1, 1<<SID_SHIFT);
                        vma = find_vma(current->mm, addr);
                        continue;
                }

                if (!vma || (addr + len) <= vma->vm_start)
                        return addr;
                addr = ALIGN(vma->vm_end, HPAGE_SIZE);
                /* Depending on segmask this might not be a confirmed
                 * hugepage region, so the ALIGN could have skipped
                 * some VMAs */
                vma = find_vma(current->mm, addr);
        }

        return -ENOMEM;
}

static unsigned long htlb_get_high_area(unsigned long len, u16 areamask)
{
        unsigned long addr = 0x100000000UL;
        struct vm_area_struct *vma;

        vma = find_vma(current->mm, addr);
        while (addr + len <= TASK_SIZE_USER64) {
                BUG_ON(vma && (addr >= vma->vm_end)); /* invariant */

                if (! __within_hugepage_high_range(addr, len, areamask)) {
                        addr = ALIGN(addr+1, 1UL<<HTLB_AREA_SHIFT);
                        vma = find_vma(current->mm, addr);
                        continue;
                }

                if (!vma || (addr + len) <= vma->vm_start)
                        return addr;
                addr = ALIGN(vma->vm_end, HPAGE_SIZE);
                /* Depending on segmask this might not be a confirmed
                 * hugepage region, so the ALIGN could have skipped
                 * some VMAs */
                vma = find_vma(current->mm, addr);
        }

        return -ENOMEM;
}

unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
                                        unsigned long len, unsigned long pgoff,
                                        unsigned long flags)
{
        int lastshift;
        u16 areamask, curareas;

        if (HPAGE_SHIFT == 0)
                return -EINVAL;
        if (len & ~HPAGE_MASK)
                return -EINVAL;

        if (!cpu_has_feature(CPU_FTR_16M_PAGE))
                return -EINVAL;

        /* Paranoia, caller should have dealt with this */
        BUG_ON((addr + len)  < addr);

        if (test_thread_flag(TIF_32BIT)) {
                /* Paranoia, caller should have dealt with this */
                BUG_ON((addr + len) > 0x100000000UL);

                curareas = current->mm->context.low_htlb_areas;

                /* First see if we can use the hint address */
                if (addr && (htlb_check_hinted_area(addr, len) == 0)) {
                        areamask = LOW_ESID_MASK(addr, len);
                        if (open_low_hpage_areas(current->mm, areamask) == 0)
                                return addr;
                }

                /* Next see if we can map in the existing low areas */
                addr = htlb_get_low_area(len, curareas);
                if (addr != -ENOMEM)
                        return addr;

                /* Finally go looking for areas to open */
                lastshift = 0;
                for (areamask = LOW_ESID_MASK(0x100000000UL-len, len);
                     ! lastshift; areamask >>=1) {
                        if (areamask & 1)
                                lastshift = 1;

                        addr = htlb_get_low_area(len, curareas | areamask);
                        if ((addr != -ENOMEM)
                            && open_low_hpage_areas(current->mm, areamask) == 0)
                                return addr;
                }
        } else {
                curareas = current->mm->context.high_htlb_areas;

                /* First see if we can use the hint address */
                /* We discourage 64-bit processes from doing hugepage
                 * mappings below 4GB (must use MAP_FIXED) */
                if ((addr >= 0x100000000UL)
                    && (htlb_check_hinted_area(addr, len) == 0)) {
                        areamask = HTLB_AREA_MASK(addr, len);
                        if (open_high_hpage_areas(current->mm, areamask) == 0)
                                return addr;
                }

                /* Next see if we can map in the existing high areas */
                addr = htlb_get_high_area(len, curareas);
                if (addr != -ENOMEM)
                        return addr;

                /* Finally go looking for areas to open */
                lastshift = 0;
                for (areamask = HTLB_AREA_MASK(TASK_SIZE_USER64-len, len);
                     ! lastshift; areamask >>=1) {
                        if (areamask & 1)
                                lastshift = 1;

                        addr = htlb_get_high_area(len, curareas | areamask);
                        if ((addr != -ENOMEM)
                            && open_high_hpage_areas(current->mm, areamask) == 0)
                                return addr;
                }
        }
        printk(KERN_DEBUG "hugetlb_get_unmapped_area() unable to open"
               " enough areas\n");
        return -ENOMEM;
}

/*
 * Called by asm hashtable.S for doing lazy icache flush
 */
static unsigned int hash_huge_page_do_lazy_icache(unsigned long rflags,
                                                  pte_t pte, int trap)
{
        struct page *page;
        int i;

        if (!pfn_valid(pte_pfn(pte)))
                return rflags;

        page = pte_page(pte);

        /* page is dirty */
        if (!test_bit(PG_arch_1, &page->flags) && !PageReserved(page)) {
                if (trap == 0x400) {
                        for (i = 0; i < (HPAGE_SIZE / PAGE_SIZE); i++)
                                __flush_dcache_icache(page_address(page+i));
                        set_bit(PG_arch_1, &page->flags);
                } else {
                        rflags |= HPTE_R_N;
                }
        }
        return rflags;
}

int hash_huge_page(struct mm_struct *mm, unsigned long access,
                   unsigned long ea, unsigned long vsid, int local,
                   unsigned long trap)
{
        pte_t *ptep;
        unsigned long old_pte, new_pte;
        unsigned long va, rflags, pa;
        long slot;
        int err = 1;

        ptep = huge_pte_offset(mm, ea);

        /* Search the Linux page table for a match with va */
        va = (vsid << 28) | (ea & 0x0fffffff);

        /*
         * If no pte found or not present, send the problem up to
         * do_page_fault
         */
        if (unlikely(!ptep || pte_none(*ptep)))
                goto out;

        /* 
         * Check the user's access rights to the page.  If access should be
         * prevented then send the problem up to do_page_fault.
         */
        if (unlikely(access & ~pte_val(*ptep)))
                goto out;
        /*
         * 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 (old_pte & _PAGE_BUSY)
                        goto out;
                new_pte = old_pte | _PAGE_BUSY |
                        _PAGE_ACCESSED | _PAGE_HASHPTE;
        } 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);
        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_huge_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, HPAGE_SHIFT);
                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_huge_psize,
                                         local) == -1)
                        old_pte &= ~_PAGE_HPTEFLAGS;
        }

        if (likely(!(old_pte & _PAGE_HASHPTE))) {
                unsigned long hash = hpt_hash(va, HPAGE_SHIFT);
                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 */
                new_pte = (new_pte & ~_PAGE_HPTEFLAGS) | _PAGE_HASHPTE;

                /* Add in WIMG bits */
                /* XXX We should store these in the pte */
                /* --BenH: I think they are ... */
                rflags |= _PAGE_COHERENT;

                /* Insert into the hash table, primary slot */
                slot = ppc_md.hpte_insert(hpte_group, va, pa, rflags, 0,
                                          mmu_huge_psize);

                /* Primary is full, try the secondary */
                if (unlikely(slot == -1)) {
                        new_pte |= _PAGE_F_SECOND;
                        hpte_group = ((~hash & htab_hash_mask) *
                                      HPTES_PER_GROUP) & ~0x7UL; 
                        slot = ppc_md.hpte_insert(hpte_group, va, pa, rflags,
                                                  HPTE_V_SECONDARY,
                                                  mmu_huge_psize);
                        if (slot == -1) {
                                if (mftb() & 0x1)
                                        hpte_group = ((hash & htab_hash_mask) *
                                                      HPTES_PER_GROUP)&~0x7UL;

                                ppc_md.hpte_remove(hpte_group);
                                goto repeat;
                        }
                }

                if (unlikely(slot == -2))
                        panic("hash_huge_page: pte_insert failed\n");

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

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

        err = 0;

 out:
        return err;
}