slice.c

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/*
 * address space "slices" (meta-segments) support
 *
 * Copyright (C) 2007 Benjamin Herrenschmidt, IBM Corporation.
 *
 * Based on hugetlb implementation
 *
 * Copyright (C) 2003 David Gibson, IBM Corporation.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#undef DEBUG

#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/pagemap.h>
#include <linux/err.h>
#include <linux/spinlock.h>
#include <linux/export.h>
#include <asm/mman.h>
#include <asm/mmu.h>
#include <asm/spu.h>

/* some sanity checks */
#if (PGTABLE_RANGE >> 43) > SLICE_MASK_SIZE
#error PGTABLE_RANGE exceeds slice_mask high_slices size
#endif

static DEFINE_SPINLOCK(slice_convert_lock);


#ifdef DEBUG
int _slice_debug = 1;

static void slice_print_mask(const char *label, struct slice_mask mask)
{
    char    *p, buf[16 + 3 + 64 + 1];
    int i;

    if (!_slice_debug)
        return;
    p = buf;
    for (i = 0; i < SLICE_NUM_LOW; i++)
        *(p++) = (mask.low_slices & (1 << i)) ? '1' : '0';
    *(p++) = ' ';
    *(p++) = '-';
    *(p++) = ' ';
    for (i = 0; i < SLICE_NUM_HIGH; i++)
        *(p++) = (mask.high_slices & (1ul << i)) ? '1' : '0';
    *(p++) = 0;

    printk(KERN_DEBUG "%s:%s\n", label, buf);
}

#define slice_dbg(fmt...) do { if (_slice_debug) pr_debug(fmt); } while(0)

#else

static void slice_print_mask(const char *label, struct slice_mask mask) {}
#define slice_dbg(fmt...)

#endif

static struct slice_mask slice_range_to_mask(unsigned long start,
                         unsigned long len)
{
    unsigned long end = start + len - 1;
    struct slice_mask ret = { 0, 0 };

    if (start < SLICE_LOW_TOP) {
        unsigned long mend = min(end, SLICE_LOW_TOP);
        unsigned long mstart = min(start, SLICE_LOW_TOP);

        ret.low_slices = (1u << (GET_LOW_SLICE_INDEX(mend) + 1))
            - (1u << GET_LOW_SLICE_INDEX(mstart));
    }

    if ((start + len) > SLICE_LOW_TOP)
        ret.high_slices = (1ul << (GET_HIGH_SLICE_INDEX(end) + 1))
            - (1ul << GET_HIGH_SLICE_INDEX(start));

    return ret;
}

static int slice_area_is_free(struct mm_struct *mm, unsigned long addr,
                  unsigned long len)
{
    struct vm_area_struct *vma;

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

static int slice_low_has_vma(struct mm_struct *mm, unsigned long slice)
{
    return !slice_area_is_free(mm, slice << SLICE_LOW_SHIFT,
                   1ul << SLICE_LOW_SHIFT);
}

static int slice_high_has_vma(struct mm_struct *mm, unsigned long slice)
{
    unsigned long start = slice << SLICE_HIGH_SHIFT;
    unsigned long end = start + (1ul << SLICE_HIGH_SHIFT);

    /* 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 = SLICE_LOW_TOP;

    return !slice_area_is_free(mm, start, end - start);
}

static struct slice_mask slice_mask_for_free(struct mm_struct *mm)
{
    struct slice_mask ret = { 0, 0 };
    unsigned long i;

    for (i = 0; i < SLICE_NUM_LOW; i++)
        if (!slice_low_has_vma(mm, i))
            ret.low_slices |= 1u << i;

    if (mm->task_size <= SLICE_LOW_TOP)
        return ret;

    for (i = 0; i < SLICE_NUM_HIGH; i++)
        if (!slice_high_has_vma(mm, i))
            ret.high_slices |= 1ul << i;

    return ret;
}

static struct slice_mask slice_mask_for_size(struct mm_struct *mm, int psize)
{
    unsigned char *hpsizes;
    int index, mask_index;
    struct slice_mask ret = { 0, 0 };
    unsigned long i;
    u64 lpsizes;

    lpsizes = mm->context.low_slices_psize;
    for (i = 0; i < SLICE_NUM_LOW; i++)
        if (((lpsizes >> (i * 4)) & 0xf) == psize)
            ret.low_slices |= 1u << i;

    hpsizes = mm->context.high_slices_psize;
    for (i = 0; i < SLICE_NUM_HIGH; i++) {
        mask_index = i & 0x1;
        index = i >> 1;
        if (((hpsizes[index] >> (mask_index * 4)) & 0xf) == psize)
            ret.high_slices |= 1ul << i;
    }

    return ret;
}

static int slice_check_fit(struct slice_mask mask, struct slice_mask available)
{
    return (mask.low_slices & available.low_slices) == mask.low_slices &&
        (mask.high_slices & available.high_slices) == mask.high_slices;
}

static void slice_flush_segments(void *parm)
{
    struct mm_struct *mm = parm;
    unsigned long flags;

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

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

    local_irq_save(flags);
    slb_flush_and_rebolt();
    local_irq_restore(flags);
}

static void slice_convert(struct mm_struct *mm, struct slice_mask mask, int psize)
{
    int index, mask_index;
    /* Write the new slice psize bits */
    unsigned char *hpsizes;
    u64 lpsizes;
    unsigned long i, flags;

    slice_dbg("slice_convert(mm=%p, psize=%d)\n", mm, psize);
    slice_print_mask(" mask", mask);

    /* We need to use a spinlock here to protect against
     * concurrent 64k -> 4k demotion ...
     */
    spin_lock_irqsave(&slice_convert_lock, flags);

    lpsizes = mm->context.low_slices_psize;
    for (i = 0; i < SLICE_NUM_LOW; i++)
        if (mask.low_slices & (1u << i))
            lpsizes = (lpsizes & ~(0xful << (i * 4))) |
                (((unsigned long)psize) << (i * 4));

    /* Assign the value back */
    mm->context.low_slices_psize = lpsizes;

    hpsizes = mm->context.high_slices_psize;
    for (i = 0; i < SLICE_NUM_HIGH; i++) {
        mask_index = i & 0x1;
        index = i >> 1;
        if (mask.high_slices & (1ul << i))
            hpsizes[index] = (hpsizes[index] &
                      ~(0xf << (mask_index * 4))) |
                (((unsigned long)psize) << (mask_index * 4));
    }

    slice_dbg(" lsps=%lx, hsps=%lx\n",
          mm->context.low_slices_psize,
          mm->context.high_slices_psize);

    spin_unlock_irqrestore(&slice_convert_lock, flags);

#ifdef CONFIG_SPU_BASE
    spu_flush_all_slbs(mm);
#endif
}

static unsigned long slice_find_area_bottomup(struct mm_struct *mm,
                          unsigned long len,
                          struct slice_mask available,
                          int psize, int use_cache)
{
    struct vm_area_struct *vma;
    unsigned long start_addr, addr;
    struct slice_mask mask;
    int pshift = max_t(int, mmu_psize_defs[psize].shift, PAGE_SHIFT);

    if (use_cache) {
        if (len <= mm->cached_hole_size) {
            start_addr = addr = TASK_UNMAPPED_BASE;
            mm->cached_hole_size = 0;
        } else
            start_addr = addr = mm->free_area_cache;
    } else
        start_addr = addr = TASK_UNMAPPED_BASE;

full_search:
    for (;;) {
        addr = _ALIGN_UP(addr, 1ul << pshift);
        if ((TASK_SIZE - len) < addr)
            break;
        vma = find_vma(mm, addr);
        BUG_ON(vma && (addr >= vma->vm_end));

        mask = slice_range_to_mask(addr, len);
        if (!slice_check_fit(mask, available)) {
            if (addr < SLICE_LOW_TOP)
                addr = _ALIGN_UP(addr + 1,  1ul << SLICE_LOW_SHIFT);
            else
                addr = _ALIGN_UP(addr + 1,  1ul << SLICE_HIGH_SHIFT);
            continue;
        }
        if (!vma || addr + len <= vma->vm_start) {
            /*
             * Remember the place where we stopped the search:
             */
            if (use_cache)
                mm->free_area_cache = addr + len;
            return addr;
        }
        if (use_cache && (addr + mm->cached_hole_size) < vma->vm_start)
                mm->cached_hole_size = vma->vm_start - addr;
        addr = vma->vm_end;
    }

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

static unsigned long slice_find_area_topdown(struct mm_struct *mm,
                         unsigned long len,
                         struct slice_mask available,
                         int psize, int use_cache)
{
    struct vm_area_struct *vma;
    unsigned long addr;
    struct slice_mask mask;
    int pshift = max_t(int, mmu_psize_defs[psize].shift, PAGE_SHIFT);

    /* check if free_area_cache is useful for us */
    if (use_cache) {
        if (len <= mm->cached_hole_size) {
            mm->cached_hole_size = 0;
            mm->free_area_cache = mm->mmap_base;
        }

        /* either no address requested or can't fit in requested
         * address hole
         */
        addr = mm->free_area_cache;

        /* make sure it can fit in the remaining address space */
        if (addr > len) {
            addr = _ALIGN_DOWN(addr - len, 1ul << pshift);
            mask = slice_range_to_mask(addr, len);
            if (slice_check_fit(mask, available) &&
                slice_area_is_free(mm, addr, len))
                    /* remember the address as a hint for
                     * next time
                     */
                    return (mm->free_area_cache = addr);
        }
    }

    addr = mm->mmap_base;
    while (addr > len) {
        /* Go down by chunk size */
        addr = _ALIGN_DOWN(addr - len, 1ul << pshift);

        /* Check for hit with different page size */
        mask = slice_range_to_mask(addr, len);
        if (!slice_check_fit(mask, available)) {
            if (addr < SLICE_LOW_TOP)
                addr = _ALIGN_DOWN(addr, 1ul << SLICE_LOW_SHIFT);
            else if (addr < (1ul << SLICE_HIGH_SHIFT))
                addr = SLICE_LOW_TOP;
            else
                addr = _ALIGN_DOWN(addr, 1ul << SLICE_HIGH_SHIFT);
            continue;
        }

        /*
         * Lookup failure means no vma is above this address,
         * else if new region fits below vma->vm_start,
         * return with success:
         */
        vma = find_vma(mm, addr);
        if (!vma || (addr + len) <= vma->vm_start) {
            /* remember the address as a hint for next time */
            if (use_cache)
                mm->free_area_cache = addr;
            return addr;
        }

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

        /* try just below the current vma->vm_start */
        addr = vma->vm_start;
    }

    /*
     * 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.
     */
    addr = slice_find_area_bottomup(mm, len, available, psize, 0);

    /*
     * Restore the topdown base:
     */
    if (use_cache) {
        mm->free_area_cache = mm->mmap_base;
        mm->cached_hole_size = ~0UL;
    }

    return addr;
}


static unsigned long slice_find_area(struct mm_struct *mm, unsigned long len,
                     struct slice_mask mask, int psize,
                     int topdown, int use_cache)
{
    if (topdown)
        return slice_find_area_topdown(mm, len, mask, psize, use_cache);
    else
        return slice_find_area_bottomup(mm, len, mask, psize, use_cache);
}

#define or_mask(dst, src)   do {            \
    (dst).low_slices |= (src).low_slices;       \
    (dst).high_slices |= (src).high_slices;     \
} while (0)

#define andnot_mask(dst, src)   do {            \
    (dst).low_slices &= ~(src).low_slices;      \
    (dst).high_slices &= ~(src).high_slices;    \
} while (0)

#ifdef CONFIG_PPC_64K_PAGES
#define MMU_PAGE_BASE   MMU_PAGE_64K
#else
#define MMU_PAGE_BASE   MMU_PAGE_4K
#endif

unsigned long slice_get_unmapped_area(unsigned long addr, unsigned long len,
                      unsigned long flags, unsigned int psize,
                      int topdown, int use_cache)
{
    struct slice_mask mask = {0, 0};
    struct slice_mask good_mask;
    struct slice_mask potential_mask = {0,0} /* silence stupid warning */;
    struct slice_mask compat_mask = {0, 0};
    int fixed = (flags & MAP_FIXED);
    int pshift = max_t(int, mmu_psize_defs[psize].shift, PAGE_SHIFT);
    struct mm_struct *mm = current->mm;
    unsigned long newaddr;

    /* Sanity checks */
    BUG_ON(mm->task_size == 0);

    slice_dbg("slice_get_unmapped_area(mm=%p, psize=%d...\n", mm, psize);
    slice_dbg(" addr=%lx, len=%lx, flags=%lx, topdown=%d, use_cache=%d\n",
          addr, len, flags, topdown, use_cache);

    if (len > mm->task_size)
        return -ENOMEM;
    if (len & ((1ul << pshift) - 1))
        return -EINVAL;
    if (fixed && (addr & ((1ul << pshift) - 1)))
        return -EINVAL;
    if (fixed && addr > (mm->task_size - len))
        return -EINVAL;

    /* If hint, make sure it matches our alignment restrictions */
    if (!fixed && addr) {
        addr = _ALIGN_UP(addr, 1ul << pshift);
        slice_dbg(" aligned addr=%lx\n", addr);
        /* Ignore hint if it's too large or overlaps a VMA */
        if (addr > mm->task_size - len ||
            !slice_area_is_free(mm, addr, len))
            addr = 0;
    }

    /* First make up a "good" mask of slices that have the right size
     * already
     */
    good_mask = slice_mask_for_size(mm, psize);
    slice_print_mask(" good_mask", good_mask);

    /*
     * Here "good" means slices that are already the right page size,
     * "compat" means slices that have a compatible page size (i.e.
     * 4k in a 64k pagesize kernel), and "free" means slices without
     * any VMAs.
     *
     * If MAP_FIXED:
     *  check if fits in good | compat => OK
     *  check if fits in good | compat | free => convert free
     *  else bad
     * If have hint:
     *  check if hint fits in good => OK
     *  check if hint fits in good | free => convert free
     * Otherwise:
     *  search in good, found => OK
     *  search in good | free, found => convert free
     *  search in good | compat | free, found => convert free.
     */

#ifdef CONFIG_PPC_64K_PAGES
    /* If we support combo pages, we can allow 64k pages in 4k slices */
    if (psize == MMU_PAGE_64K) {
        compat_mask = slice_mask_for_size(mm, MMU_PAGE_4K);
        if (fixed)
            or_mask(good_mask, compat_mask);
    }
#endif

    /* First check hint if it's valid or if we have MAP_FIXED */
    if (addr != 0 || fixed) {
        /* Build a mask for the requested range */
        mask = slice_range_to_mask(addr, len);
        slice_print_mask(" mask", mask);

        /* Check if we fit in the good mask. If we do, we just return,
         * nothing else to do
         */
        if (slice_check_fit(mask, good_mask)) {
            slice_dbg(" fits good !\n");
            return addr;
        }
    } else {
        /* Now let's see if we can find something in the existing
         * slices for that size
         */
        newaddr = slice_find_area(mm, len, good_mask, psize, topdown,
                      use_cache);
        if (newaddr != -ENOMEM) {
            /* Found within the good mask, we don't have to setup,
             * we thus return directly
             */
            slice_dbg(" found area at 0x%lx\n", newaddr);
            return newaddr;
        }
    }

    /* We don't fit in the good mask, check what other slices are
     * empty and thus can be converted
     */
    potential_mask = slice_mask_for_free(mm);
    or_mask(potential_mask, good_mask);
    slice_print_mask(" potential", potential_mask);

    if ((addr != 0 || fixed) && slice_check_fit(mask, potential_mask)) {
        slice_dbg(" fits potential !\n");
        goto convert;
    }

    /* If we have MAP_FIXED and failed the above steps, then error out */
    if (fixed)
        return -EBUSY;

    slice_dbg(" search...\n");

    /* If we had a hint that didn't work out, see if we can fit
     * anywhere in the good area.
     */
    if (addr) {
        addr = slice_find_area(mm, len, good_mask, psize, topdown,
                       use_cache);
        if (addr != -ENOMEM) {
            slice_dbg(" found area at 0x%lx\n", addr);
            return addr;
        }
    }

    /* Now let's see if we can find something in the existing slices
     * for that size plus free slices
     */
    addr = slice_find_area(mm, len, potential_mask, psize, topdown,
                   use_cache);

#ifdef CONFIG_PPC_64K_PAGES
    if (addr == -ENOMEM && psize == MMU_PAGE_64K) {
        /* retry the search with 4k-page slices included */
        or_mask(potential_mask, compat_mask);
        addr = slice_find_area(mm, len, potential_mask, psize,
                       topdown, use_cache);
    }
#endif

    if (addr == -ENOMEM)
        return -ENOMEM;

    mask = slice_range_to_mask(addr, len);
    slice_dbg(" found potential area at 0x%lx\n", addr);
    slice_print_mask(" mask", mask);

 convert:
    andnot_mask(mask, good_mask);
    andnot_mask(mask, compat_mask);
    if (mask.low_slices || mask.high_slices) {
        slice_convert(mm, mask, psize);
        if (psize > MMU_PAGE_BASE)
            on_each_cpu(slice_flush_segments, mm, 1);
    }
    return addr;

}
EXPORT_SYMBOL_GPL(slice_get_unmapped_area);

unsigned long arch_get_unmapped_area(struct file *filp,
                     unsigned long addr,
                     unsigned long len,
                     unsigned long pgoff,
                     unsigned long flags)
{
    return slice_get_unmapped_area(addr, len, flags,
                       current->mm->context.user_psize,
                       0, 1);
}

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)
{
    return slice_get_unmapped_area(addr0, len, flags,
                       current->mm->context.user_psize,
                       1, 1);
}

unsigned int get_slice_psize(struct mm_struct *mm, unsigned long addr)
{
    unsigned char *hpsizes;
    int index, mask_index;

    if (addr < SLICE_LOW_TOP) {
        u64 lpsizes;
        lpsizes = mm->context.low_slices_psize;
        index = GET_LOW_SLICE_INDEX(addr);
        return (lpsizes >> (index * 4)) & 0xf;
    }
    hpsizes = mm->context.high_slices_psize;
    index = GET_HIGH_SLICE_INDEX(addr);
    mask_index = index & 0x1;
    return (hpsizes[index >> 1] >> (mask_index * 4)) & 0xf;
}
EXPORT_SYMBOL_GPL(get_slice_psize);

/*
 * This is called by hash_page when it needs to do a lazy conversion of
 * an address space from real 64K pages to combo 4K pages (typically
 * when hitting a non cacheable mapping on a processor or hypervisor
 * that won't allow them for 64K pages).
 *
 * This is also called in init_new_context() to change back the user
 * psize from whatever the parent context had it set to
 * N.B. This may be called before mm->context.id has been set.
 *
 * This function will only change the content of the {low,high)_slice_psize
 * masks, it will not flush SLBs as this shall be handled lazily by the
 * caller.
 */
void slice_set_user_psize(struct mm_struct *mm, unsigned int psize)
{
    int index, mask_index;
    unsigned char *hpsizes;
    unsigned long flags, lpsizes;
    unsigned int old_psize;
    int i;

    slice_dbg("slice_set_user_psize(mm=%p, psize=%d)\n", mm, psize);

    spin_lock_irqsave(&slice_convert_lock, flags);

    old_psize = mm->context.user_psize;
    slice_dbg(" old_psize=%d\n", old_psize);
    if (old_psize == psize)
        goto bail;

    mm->context.user_psize = psize;
    wmb();

    lpsizes = mm->context.low_slices_psize;
    for (i = 0; i < SLICE_NUM_LOW; i++)
        if (((lpsizes >> (i * 4)) & 0xf) == old_psize)
            lpsizes = (lpsizes & ~(0xful << (i * 4))) |
                (((unsigned long)psize) << (i * 4));
    /* Assign the value back */
    mm->context.low_slices_psize = lpsizes;

    hpsizes = mm->context.high_slices_psize;
    for (i = 0; i < SLICE_NUM_HIGH; i++) {
        mask_index = i & 0x1;
        index = i >> 1;
        if (((hpsizes[index] >> (mask_index * 4)) & 0xf) == old_psize)
            hpsizes[index] = (hpsizes[index] &
                      ~(0xf << (mask_index * 4))) |
                (((unsigned long)psize) << (mask_index * 4));
    }




    slice_dbg(" lsps=%lx, hsps=%lx\n",
          mm->context.low_slices_psize,
          mm->context.high_slices_psize);

 bail:
    spin_unlock_irqrestore(&slice_convert_lock, flags);
}

void slice_set_psize(struct mm_struct *mm, unsigned long address,
             unsigned int psize)
{
    unsigned char *hpsizes;
    unsigned long i, flags;
    u64 *lpsizes;

    spin_lock_irqsave(&slice_convert_lock, flags);
    if (address < SLICE_LOW_TOP) {
        i = GET_LOW_SLICE_INDEX(address);
        lpsizes = &mm->context.low_slices_psize;
        *lpsizes = (*lpsizes & ~(0xful << (i * 4))) |
            ((unsigned long) psize << (i * 4));
    } else {
        int index, mask_index;
        i = GET_HIGH_SLICE_INDEX(address);
        hpsizes = mm->context.high_slices_psize;
        mask_index = i & 0x1;
        index = i >> 1;
        hpsizes[index] = (hpsizes[index] &
                  ~(0xf << (mask_index * 4))) |
            (((unsigned long)psize) << (mask_index * 4));
    }

    spin_unlock_irqrestore(&slice_convert_lock, flags);

#ifdef CONFIG_SPU_BASE
    spu_flush_all_slbs(mm);
#endif
}

void slice_set_range_psize(struct mm_struct *mm, unsigned long start,
               unsigned long len, unsigned int psize)
{
    struct slice_mask mask = slice_range_to_mask(start, len);

    slice_convert(mm, mask, psize);
}

/*
 * is_hugepage_only_range() is used by generic code to verify wether
 * a normal mmap mapping (non hugetlbfs) is valid on a given area.
 *
 * until the generic code provides a more generic hook and/or starts
 * calling arch get_unmapped_area for MAP_FIXED (which our implementation
 * here knows how to deal with), we hijack it to keep standard mappings
 * away from us.
 *
 * because of that generic code limitation, MAP_FIXED mapping cannot
 * "convert" back a slice with no VMAs to the standard page size, only
 * get_unmapped_area() can. It would be possible to fix it here but I
 * prefer working on fixing the generic code instead.
 *
 * WARNING: This will not work if hugetlbfs isn't enabled since the
 * generic code will redefine that function as 0 in that. This is ok
 * for now as we only use slices with hugetlbfs enabled. This should
 * be fixed as the generic code gets fixed.
 */
int is_hugepage_only_range(struct mm_struct *mm, unsigned long addr,
               unsigned long len)
{
    struct slice_mask mask, available;
    unsigned int psize = mm->context.user_psize;

    mask = slice_range_to_mask(addr, len);
    available = slice_mask_for_size(mm, psize);
#ifdef CONFIG_PPC_64K_PAGES
    /* We need to account for 4k slices too */
    if (psize == MMU_PAGE_64K) {
        struct slice_mask compat_mask;
        compat_mask = slice_mask_for_size(mm, MMU_PAGE_4K);
        or_mask(available, compat_mask);
    }
#endif

#if 0 /* too verbose */
    slice_dbg("is_hugepage_only_range(mm=%p, addr=%lx, len=%lx)\n",
         mm, addr, len);
    slice_print_mask(" mask", mask);
    slice_print_mask(" available", available);
#endif
    return !slice_check_fit(mask, available);
}