[safe/jmp/linux-2.6] / arch / x86 / mm / pat.c

/*
 * Handle caching attributes in page tables (PAT)
 *
 * Authors: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
 *          Suresh B Siddha <suresh.b.siddha@intel.com>
 *
 * Loosely based on earlier PAT patchset from Eric Biederman and Andi Kleen.
 */

#include <linux/seq_file.h>
#include <linux/bootmem.h>
#include <linux/debugfs.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/gfp.h>
#include <linux/mm.h>
#include <linux/fs.h>
#include <linux/rbtree.h>

#include <asm/cacheflush.h>
#include <asm/processor.h>
#include <asm/tlbflush.h>
#include <asm/pgtable.h>
#include <asm/fcntl.h>
#include <asm/e820.h>
#include <asm/mtrr.h>
#include <asm/page.h>
#include <asm/msr.h>
#include <asm/pat.h>
#include <asm/io.h>

#ifdef CONFIG_X86_PAT
int __read_mostly pat_enabled = 1;

static inline void pat_disable(const char *reason)
{
        pat_enabled = 0;
        printk(KERN_INFO "%s\n", reason);
}

static int __init nopat(char *str)
{
        pat_disable("PAT support disabled.");
        return 0;
}
early_param("nopat", nopat);
#else
static inline void pat_disable(const char *reason)
{
        (void)reason;
}
#endif


static int debug_enable;

static int __init pat_debug_setup(char *str)
{
        debug_enable = 1;
        return 0;
}
__setup("debugpat", pat_debug_setup);

#define dprintk(fmt, arg...) \
        do { if (debug_enable) printk(KERN_INFO fmt, ##arg); } while (0)


static u64 __read_mostly boot_pat_state;

enum {
        PAT_UC = 0,             /* uncached */
        PAT_WC = 1,             /* Write combining */
        PAT_WT = 4,             /* Write Through */
        PAT_WP = 5,             /* Write Protected */
        PAT_WB = 6,             /* Write Back (default) */
        PAT_UC_MINUS = 7,       /* UC, but can be overriden by MTRR */
};

#define PAT(x, y)       ((u64)PAT_ ## y << ((x)*8))

void pat_init(void)
{
        u64 pat;

        if (!pat_enabled)
                return;

        if (!cpu_has_pat) {
                if (!boot_pat_state) {
                        pat_disable("PAT not supported by CPU.");
                        return;
                } else {
                        /*
                         * If this happens we are on a secondary CPU, but
                         * switched to PAT on the boot CPU. We have no way to
                         * undo PAT.
                         */
                        printk(KERN_ERR "PAT enabled, "
                               "but not supported by secondary CPU\n");
                        BUG();
                }
        }

        /* Set PWT to Write-Combining. All other bits stay the same */
        /*
         * PTE encoding used in Linux:
         *      PAT
         *      |PCD
         *      ||PWT
         *      |||
         *      000 WB          _PAGE_CACHE_WB
         *      001 WC          _PAGE_CACHE_WC
         *      010 UC-         _PAGE_CACHE_UC_MINUS
         *      011 UC          _PAGE_CACHE_UC
         * PAT bit unused
         */
        pat = PAT(0, WB) | PAT(1, WC) | PAT(2, UC_MINUS) | PAT(3, UC) |
              PAT(4, WB) | PAT(5, WC) | PAT(6, UC_MINUS) | PAT(7, UC);

        /* Boot CPU check */
        if (!boot_pat_state)
                rdmsrl(MSR_IA32_CR_PAT, boot_pat_state);

        wrmsrl(MSR_IA32_CR_PAT, pat);
        printk(KERN_INFO "x86 PAT enabled: cpu %d, old 0x%Lx, new 0x%Lx\n",
               smp_processor_id(), boot_pat_state, pat);
}

#undef PAT

static char *cattr_name(unsigned long flags)
{
        switch (flags & _PAGE_CACHE_MASK) {
        case _PAGE_CACHE_UC:            return "uncached";
        case _PAGE_CACHE_UC_MINUS:      return "uncached-minus";
        case _PAGE_CACHE_WB:            return "write-back";
        case _PAGE_CACHE_WC:            return "write-combining";
        default:                        return "broken";
        }
}

/*
 * The global memtype list keeps track of memory type for specific
 * physical memory areas. Conflicting memory types in different
 * mappings can cause CPU cache corruption. To avoid this we keep track.
 *
 * The list is sorted based on starting address and can contain multiple
 * entries for each address (this allows reference counting for overlapping
 * areas). All the aliases have the same cache attributes of course.
 * Zero attributes are represented as holes.
 *
 * The data structure is a list that is also organized as an rbtree
 * sorted on the start address of memtype range.
 *
 * memtype_lock protects both the linear list and rbtree.
 */

struct memtype {
        u64                     start;
        u64                     end;
        unsigned long           type;
        struct list_head        nd;
        struct rb_node          rb;
};

static struct rb_root memtype_rbroot = RB_ROOT;
static LIST_HEAD(memtype_list);
static DEFINE_SPINLOCK(memtype_lock);   /* protects memtype list */

static struct memtype *memtype_rb_search(struct rb_root *root, u64 start)
{
        struct rb_node *node = root->rb_node;
        struct memtype *last_lower = NULL;

        while (node) {
                struct memtype *data = container_of(node, struct memtype, rb);

                if (data->start < start) {
                        last_lower = data;
                        node = node->rb_right;
                } else if (data->start > start) {
                        node = node->rb_left;
                } else
                        return data;
        }

        /* Will return NULL if there is no entry with its start <= start */
        return last_lower;
}

static void memtype_rb_insert(struct rb_root *root, struct memtype *data)
{
        struct rb_node **new = &(root->rb_node);
        struct rb_node *parent = NULL;

        while (*new) {
                struct memtype *this = container_of(*new, struct memtype, rb);

                parent = *new;
                if (data->start <= this->start)
                        new = &((*new)->rb_left);
                else if (data->start > this->start)
                        new = &((*new)->rb_right);
        }

        rb_link_node(&data->rb, parent, new);
        rb_insert_color(&data->rb, root);
}

/*
 * Does intersection of PAT memory type and MTRR memory type and returns
 * the resulting memory type as PAT understands it.
 * (Type in pat and mtrr will not have same value)
 * The intersection is based on "Effective Memory Type" tables in IA-32
 * SDM vol 3a
 */
static unsigned long pat_x_mtrr_type(u64 start, u64 end, unsigned long req_type)
{
        /*
         * Look for MTRR hint to get the effective type in case where PAT
         * request is for WB.
         */
        if (req_type == _PAGE_CACHE_WB) {
                u8 mtrr_type;

                mtrr_type = mtrr_type_lookup(start, end);
                if (mtrr_type != MTRR_TYPE_WRBACK)
                        return _PAGE_CACHE_UC_MINUS;

                return _PAGE_CACHE_WB;
        }

        return req_type;
}

static int
chk_conflict(struct memtype *new, struct memtype *entry, unsigned long *type)
{
        if (new->type != entry->type) {
                if (type) {
                        new->type = entry->type;
                        *type = entry->type;
                } else
                        goto conflict;
        }

         /* check overlaps with more than one entry in the list */
        list_for_each_entry_continue(entry, &memtype_list, nd) {
                if (new->end <= entry->start)
                        break;
                else if (new->type != entry->type)
                        goto conflict;
        }
        return 0;

 conflict:
        printk(KERN_INFO "%s:%d conflicting memory types "
               "%Lx-%Lx %s<->%s\n", current->comm, current->pid, new->start,
               new->end, cattr_name(new->type), cattr_name(entry->type));
        return -EBUSY;
}

static int pat_pagerange_is_ram(unsigned long start, unsigned long end)
{
        int ram_page = 0, not_rampage = 0;
        unsigned long page_nr;

        for (page_nr = (start >> PAGE_SHIFT); page_nr < (end >> PAGE_SHIFT);
             ++page_nr) {
                /*
                 * For legacy reasons, physical address range in the legacy ISA
                 * region is tracked as non-RAM. This will allow users of
                 * /dev/mem to map portions of legacy ISA region, even when
                 * some of those portions are listed(or not even listed) with
                 * different e820 types(RAM/reserved/..)
                 */
                if (page_nr >= (ISA_END_ADDRESS >> PAGE_SHIFT) &&
                    page_is_ram(page_nr))
                        ram_page = 1;
                else
                        not_rampage = 1;

                if (ram_page == not_rampage)
                        return -1;
        }

        return ram_page;
}

/*
 * For RAM pages, mark the pages as non WB memory type using
 * PageNonWB (PG_arch_1). We allow only one set_memory_uc() or
 * set_memory_wc() on a RAM page at a time before marking it as WB again.
 * This is ok, because only one driver will be owning the page and
 * doing set_memory_*() calls.
 *
 * For now, we use PageNonWB to track that the RAM page is being mapped
 * as non WB. In future, we will have to use one more flag
 * (or some other mechanism in page_struct) to distinguish between
 * UC and WC mapping.
 */
static int reserve_ram_pages_type(u64 start, u64 end, unsigned long req_type,
                                  unsigned long *new_type)
{
        struct page *page;
        u64 pfn, end_pfn;

        for (pfn = (start >> PAGE_SHIFT); pfn < (end >> PAGE_SHIFT); ++pfn) {
                page = pfn_to_page(pfn);
                if (page_mapped(page) || PageNonWB(page))
                        goto out;

                SetPageNonWB(page);
        }
        return 0;

out:
        end_pfn = pfn;
        for (pfn = (start >> PAGE_SHIFT); pfn < end_pfn; ++pfn) {
                page = pfn_to_page(pfn);
                ClearPageNonWB(page);
        }

        return -EINVAL;
}

static int free_ram_pages_type(u64 start, u64 end)
{
        struct page *page;
        u64 pfn, end_pfn;

        for (pfn = (start >> PAGE_SHIFT); pfn < (end >> PAGE_SHIFT); ++pfn) {
                page = pfn_to_page(pfn);
                if (page_mapped(page) || !PageNonWB(page))
                        goto out;

                ClearPageNonWB(page);
        }
        return 0;

out:
        end_pfn = pfn;
        for (pfn = (start >> PAGE_SHIFT); pfn < end_pfn; ++pfn) {
                page = pfn_to_page(pfn);
                SetPageNonWB(page);
        }
        return -EINVAL;
}

/*
 * req_type typically has one of the:
 * - _PAGE_CACHE_WB
 * - _PAGE_CACHE_WC
 * - _PAGE_CACHE_UC_MINUS
 * - _PAGE_CACHE_UC
 *
 * req_type will have a special case value '-1', when requester want to inherit
 * the memory type from mtrr (if WB), existing PAT, defaulting to UC_MINUS.
 *
 * If new_type is NULL, function will return an error if it cannot reserve the
 * region with req_type. If new_type is non-NULL, function will return
 * available type in new_type in case of no error. In case of any error
 * it will return a negative return value.
 */
int reserve_memtype(u64 start, u64 end, unsigned long req_type,
                    unsigned long *new_type)
{
        struct memtype *new, *entry;
        unsigned long actual_type;
        struct list_head *where;
        int is_range_ram;
        int err = 0;

        BUG_ON(start >= end); /* end is exclusive */

        if (!pat_enabled) {
                /* This is identical to page table setting without PAT */
                if (new_type) {
                        if (req_type == -1)
                                *new_type = _PAGE_CACHE_WB;
                        else if (req_type == _PAGE_CACHE_WC)
                                *new_type = _PAGE_CACHE_UC_MINUS;
                        else
                                *new_type = req_type & _PAGE_CACHE_MASK;
                }
                return 0;
        }

        /* Low ISA region is always mapped WB in page table. No need to track */
        if (is_ISA_range(start, end - 1)) {
                if (new_type)
                        *new_type = _PAGE_CACHE_WB;
                return 0;
        }

        /*
         * Call mtrr_lookup to get the type hint. This is an
         * optimization for /dev/mem mmap'ers into WB memory (BIOS
         * tools and ACPI tools). Use WB request for WB memory and use
         * UC_MINUS otherwise.
         */
        actual_type = pat_x_mtrr_type(start, end, req_type & _PAGE_CACHE_MASK);

        if (new_type)
                *new_type = actual_type;

        is_range_ram = pat_pagerange_is_ram(start, end);
        if (is_range_ram == 1)
                return reserve_ram_pages_type(start, end, req_type,
                                              new_type);
        else if (is_range_ram < 0)
                return -EINVAL;

        new  = kmalloc(sizeof(struct memtype), GFP_KERNEL);
        if (!new)
                return -ENOMEM;

        new->start      = start;
        new->end        = end;
        new->type       = actual_type;

        spin_lock(&memtype_lock);

        entry = memtype_rb_search(&memtype_rbroot, new->start);
        if (likely(entry != NULL)) {
                /* To work correctly with list_for_each_entry_continue */
                entry = list_entry(entry->nd.prev, struct memtype, nd);
        } else {
                entry = list_entry(&memtype_list, struct memtype, nd);
        }

        /* Search for existing mapping that overlaps the current range */
        where = NULL;
        list_for_each_entry_continue(entry, &memtype_list, nd) {
                if (end <= entry->start) {
                        where = entry->nd.prev;
                        break;
                } else if (start <= entry->start) { /* end > entry->start */
                        err = chk_conflict(new, entry, new_type);
                        if (!err) {
                                dprintk("Overlap at 0x%Lx-0x%Lx\n",
                                        entry->start, entry->end);
                                where = entry->nd.prev;
                        }
                        break;
                } else if (start < entry->end) { /* start > entry->start */
                        err = chk_conflict(new, entry, new_type);
                        if (!err) {
                                dprintk("Overlap at 0x%Lx-0x%Lx\n",
                                        entry->start, entry->end);

                                /*
                                 * Move to right position in the linked
                                 * list to add this new entry
                                 */
                                list_for_each_entry_continue(entry,
                                                        &memtype_list, nd) {
                                        if (start <= entry->start) {
                                                where = entry->nd.prev;
                                                break;
                                        }
                                }
                        }
                        break;
                }
        }

        if (err) {
                printk(KERN_INFO "reserve_memtype failed 0x%Lx-0x%Lx, "
                       "track %s, req %s\n",
                       start, end, cattr_name(new->type), cattr_name(req_type));
                kfree(new);
                spin_unlock(&memtype_lock);

                return err;
        }

        if (where)
                list_add(&new->nd, where);
        else
                list_add_tail(&new->nd, &memtype_list);

        memtype_rb_insert(&memtype_rbroot, new);

        spin_unlock(&memtype_lock);

        dprintk("reserve_memtype added 0x%Lx-0x%Lx, track %s, req %s, ret %s\n",
                start, end, cattr_name(new->type), cattr_name(req_type),
                new_type ? cattr_name(*new_type) : "-");

        return err;
}

int free_memtype(u64 start, u64 end)
{
        struct memtype *entry, *saved_entry;
        int err = -EINVAL;
        int is_range_ram;

        if (!pat_enabled)
                return 0;

        /* Low ISA region is always mapped WB. No need to track */
        if (is_ISA_range(start, end - 1))
                return 0;

        is_range_ram = pat_pagerange_is_ram(start, end);
        if (is_range_ram == 1)
                return free_ram_pages_type(start, end);
        else if (is_range_ram < 0)
                return -EINVAL;

        spin_lock(&memtype_lock);

        entry = memtype_rb_search(&memtype_rbroot, start);
        if (unlikely(entry == NULL))
                goto unlock_ret;

        /*
         * Saved entry points to an entry with start same or less than what
         * we searched for. Now go through the list in both directions to look
         * for the entry that matches with both start and end, with list stored
         * in sorted start address
         */
        saved_entry = entry;
        list_for_each_entry(entry, &memtype_list, nd) {
                if (entry->start == start && entry->end == end) {
                        rb_erase(&entry->rb, &memtype_rbroot);
                        list_del(&entry->nd);
                        kfree(entry);
                        err = 0;
                        break;
                } else if (entry->start > start) {
                        break;
                }
        }

        if (!err)
                goto unlock_ret;

        entry = saved_entry;
        list_for_each_entry_reverse(entry, &memtype_list, nd) {
                if (entry->start == start && entry->end == end) {
                        rb_erase(&entry->rb, &memtype_rbroot);
                        list_del(&entry->nd);
                        kfree(entry);
                        err = 0;
                        break;
                } else if (entry->start < start) {
                        break;
                }
        }
unlock_ret:
        spin_unlock(&memtype_lock);

        if (err) {
                printk(KERN_INFO "%s:%d freeing invalid memtype %Lx-%Lx\n",
                        current->comm, current->pid, start, end);
        }

        dprintk("free_memtype request 0x%Lx-0x%Lx\n", start, end);

        return err;
}


/**
 * io_reserve_memtype - Request a memory type mapping for a region of memory
 * @start: start (physical address) of the region
 * @end: end (physical address) of the region
 * @type: A pointer to memtype, with requested type. On success, requested
 * or any other compatible type that was available for the region is returned
 *
 * On success, returns 0
 * On failure, returns non-zero
 */
int io_reserve_memtype(resource_size_t start, resource_size_t end,
                        unsigned long *type)
{
        unsigned long req_type = *type;
        unsigned long new_type;
        int ret;

        WARN_ON_ONCE(iomem_map_sanity_check(start, end - start));

        ret = reserve_memtype(start, end, req_type, &new_type);
        if (ret)
                goto out_err;

        if (!is_new_memtype_allowed(req_type, new_type))
                goto out_free;

        if (kernel_map_sync_memtype(start, end - start, new_type) < 0)
                goto out_free;

        *type = new_type;
        return 0;

out_free:
        free_memtype(start, end);
        ret = -EBUSY;
out_err:
        return ret;
}

/**
 * io_free_memtype - Release a memory type mapping for a region of memory
 * @start: start (physical address) of the region
 * @end: end (physical address) of the region
 */
void io_free_memtype(resource_size_t start, resource_size_t end)
{
        free_memtype(start, end);
}

pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
                                unsigned long size, pgprot_t vma_prot)
{
        return vma_prot;
}

#ifdef CONFIG_STRICT_DEVMEM
/* This check is done in drivers/char/mem.c in case of STRICT_DEVMEM*/
static inline int range_is_allowed(unsigned long pfn, unsigned long size)
{
        return 1;
}
#else
/* This check is needed to avoid cache aliasing when PAT is enabled */
static inline int range_is_allowed(unsigned long pfn, unsigned long size)
{
        u64 from = ((u64)pfn) << PAGE_SHIFT;
        u64 to = from + size;
        u64 cursor = from;

        if (!pat_enabled)
                return 1;

        while (cursor < to) {
                if (!devmem_is_allowed(pfn)) {
                        printk(KERN_INFO
                "Program %s tried to access /dev/mem between %Lx->%Lx.\n",
                                current->comm, from, to);
                        return 0;
                }
                cursor += PAGE_SIZE;
                pfn++;
        }
        return 1;
}
#endif /* CONFIG_STRICT_DEVMEM */

int phys_mem_access_prot_allowed(struct file *file, unsigned long pfn,
                                unsigned long size, pgprot_t *vma_prot)
{
        unsigned long flags = _PAGE_CACHE_WB;

        if (!range_is_allowed(pfn, size))
                return 0;

        if (file->f_flags & O_SYNC) {
                flags = _PAGE_CACHE_UC_MINUS;
        }

#ifdef CONFIG_X86_32
        /*
         * On the PPro and successors, the MTRRs are used to set
         * memory types for physical addresses outside main memory,
         * so blindly setting UC or PWT on those pages is wrong.
         * For Pentiums and earlier, the surround logic should disable
         * caching for the high addresses through the KEN pin, but
         * we maintain the tradition of paranoia in this code.
         */
        if (!pat_enabled &&
            !(boot_cpu_has(X86_FEATURE_MTRR) ||
              boot_cpu_has(X86_FEATURE_K6_MTRR) ||
              boot_cpu_has(X86_FEATURE_CYRIX_ARR) ||
              boot_cpu_has(X86_FEATURE_CENTAUR_MCR)) &&
            (pfn << PAGE_SHIFT) >= __pa(high_memory)) {
                flags = _PAGE_CACHE_UC;
        }
#endif

        *vma_prot = __pgprot((pgprot_val(*vma_prot) & ~_PAGE_CACHE_MASK) |
                             flags);
        return 1;
}

/*
 * Change the memory type for the physial address range in kernel identity
 * mapping space if that range is a part of identity map.
 */
int kernel_map_sync_memtype(u64 base, unsigned long size, unsigned long flags)
{
        unsigned long id_sz;

        if (base >= __pa(high_memory))
                return 0;

        id_sz = (__pa(high_memory) < base + size) ?
                                __pa(high_memory) - base :
                                size;

        if (ioremap_change_attr((unsigned long)__va(base), id_sz, flags) < 0) {
                printk(KERN_INFO
                        "%s:%d ioremap_change_attr failed %s "
                        "for %Lx-%Lx\n",
                        current->comm, current->pid,
                        cattr_name(flags),
                        base, (unsigned long long)(base + size));
                return -EINVAL;
        }
        return 0;
}

/*
 * Internal interface to reserve a range of physical memory with prot.
 * Reserved non RAM regions only and after successful reserve_memtype,
 * this func also keeps identity mapping (if any) in sync with this new prot.
 */
static int reserve_pfn_range(u64 paddr, unsigned long size, pgprot_t *vma_prot,
                                int strict_prot)
{
        int is_ram = 0;
        int ret;
        unsigned long want_flags = (pgprot_val(*vma_prot) & _PAGE_CACHE_MASK);
        unsigned long flags = want_flags;

        is_ram = pat_pagerange_is_ram(paddr, paddr + size);

        /*
         * reserve_pfn_range() doesn't support RAM pages. Maintain the current
         * behavior with RAM pages by returning success.
         */
        if (is_ram != 0)
                return 0;

        ret = reserve_memtype(paddr, paddr + size, want_flags, &flags);
        if (ret)
                return ret;

        if (flags != want_flags) {
                if (strict_prot || !is_new_memtype_allowed(want_flags, flags)) {
                        free_memtype(paddr, paddr + size);
                        printk(KERN_ERR "%s:%d map pfn expected mapping type %s"
                                " for %Lx-%Lx, got %s\n",
                                current->comm, current->pid,
                                cattr_name(want_flags),
                                (unsigned long long)paddr,
                                (unsigned long long)(paddr + size),
                                cattr_name(flags));
                        return -EINVAL;
                }
                /*
                 * We allow returning different type than the one requested in
                 * non strict case.
                 */
                *vma_prot = __pgprot((pgprot_val(*vma_prot) &
                                      (~_PAGE_CACHE_MASK)) |
                                     flags);
        }

        if (kernel_map_sync_memtype(paddr, size, flags) < 0) {
                free_memtype(paddr, paddr + size);
                return -EINVAL;
        }
        return 0;
}

/*
 * Internal interface to free a range of physical memory.
 * Frees non RAM regions only.
 */
static void free_pfn_range(u64 paddr, unsigned long size)
{
        int is_ram;

        is_ram = pat_pagerange_is_ram(paddr, paddr + size);
        if (is_ram == 0)
                free_memtype(paddr, paddr + size);
}

/*
 * track_pfn_vma_copy is called when vma that is covering the pfnmap gets
 * copied through copy_page_range().
 *
 * If the vma has a linear pfn mapping for the entire range, we get the prot
 * from pte and reserve the entire vma range with single reserve_pfn_range call.
 */
int track_pfn_vma_copy(struct vm_area_struct *vma)
{
        resource_size_t paddr;
        unsigned long prot;
        unsigned long vma_size = vma->vm_end - vma->vm_start;
        pgprot_t pgprot;

        /*
         * For now, only handle remap_pfn_range() vmas where
         * is_linear_pfn_mapping() == TRUE. Handling of
         * vm_insert_pfn() is TBD.
         */
        if (is_linear_pfn_mapping(vma)) {
                /*
                 * reserve the whole chunk covered by vma. We need the
                 * starting address and protection from pte.
                 */
                if (follow_phys(vma, vma->vm_start, 0, &prot, &paddr)) {
                        WARN_ON_ONCE(1);
                        return -EINVAL;
                }
                pgprot = __pgprot(prot);
                return reserve_pfn_range(paddr, vma_size, &pgprot, 1);
        }

        return 0;
}

/*
 * track_pfn_vma_new is called when a _new_ pfn mapping is being established
 * for physical range indicated by pfn and size.
 *
 * prot is passed in as a parameter for the new mapping. If the vma has a
 * linear pfn mapping for the entire range reserve the entire vma range with
 * single reserve_pfn_range call.
 */
int track_pfn_vma_new(struct vm_area_struct *vma, pgprot_t *prot,
                        unsigned long pfn, unsigned long size)
{
        resource_size_t paddr;
        unsigned long vma_size = vma->vm_end - vma->vm_start;

        /*
         * For now, only handle remap_pfn_range() vmas where
         * is_linear_pfn_mapping() == TRUE. Handling of
         * vm_insert_pfn() is TBD.
         */
        if (is_linear_pfn_mapping(vma)) {
                /* reserve the whole chunk starting from vm_pgoff */
                paddr = (resource_size_t)vma->vm_pgoff << PAGE_SHIFT;
                return reserve_pfn_range(paddr, vma_size, prot, 0);
        }

        return 0;
}

/*
 * untrack_pfn_vma is called while unmapping a pfnmap for a region.
 * untrack can be called for a specific region indicated by pfn and size or
 * can be for the entire vma (in which case size can be zero).
 */
void untrack_pfn_vma(struct vm_area_struct *vma, unsigned long pfn,
                        unsigned long size)
{
        resource_size_t paddr;
        unsigned long vma_size = vma->vm_end - vma->vm_start;

        /*
         * For now, only handle remap_pfn_range() vmas where
         * is_linear_pfn_mapping() == TRUE. Handling of
         * vm_insert_pfn() is TBD.
         */
        if (is_linear_pfn_mapping(vma)) {
                /* free the whole chunk starting from vm_pgoff */
                paddr = (resource_size_t)vma->vm_pgoff << PAGE_SHIFT;
                free_pfn_range(paddr, vma_size);
                return;
        }
}

pgprot_t pgprot_writecombine(pgprot_t prot)
{
        if (pat_enabled)
                return __pgprot(pgprot_val(prot) | _PAGE_CACHE_WC);
        else
                return pgprot_noncached(prot);
}
EXPORT_SYMBOL_GPL(pgprot_writecombine);

#if defined(CONFIG_DEBUG_FS) && defined(CONFIG_X86_PAT)

/* get Nth element of the linked list */
static struct memtype *memtype_get_idx(loff_t pos)
{
        struct memtype *list_node, *print_entry;
        int i = 1;

        print_entry  = kmalloc(sizeof(struct memtype), GFP_KERNEL);
        if (!print_entry)
                return NULL;

        spin_lock(&memtype_lock);
        list_for_each_entry(list_node, &memtype_list, nd) {
                if (pos == i) {
                        *print_entry = *list_node;
                        spin_unlock(&memtype_lock);
                        return print_entry;
                }
                ++i;
        }
        spin_unlock(&memtype_lock);
        kfree(print_entry);

        return NULL;
}

static void *memtype_seq_start(struct seq_file *seq, loff_t *pos)
{
        if (*pos == 0) {
                ++*pos;
                seq_printf(seq, "PAT memtype list:\n");
        }

        return memtype_get_idx(*pos);
}

static void *memtype_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
        ++*pos;
        return memtype_get_idx(*pos);
}

static void memtype_seq_stop(struct seq_file *seq, void *v)
{
}

static int memtype_seq_show(struct seq_file *seq, void *v)
{
        struct memtype *print_entry = (struct memtype *)v;

        seq_printf(seq, "%s @ 0x%Lx-0x%Lx\n", cattr_name(print_entry->type),
                        print_entry->start, print_entry->end);
        kfree(print_entry);

        return 0;
}

static struct seq_operations memtype_seq_ops = {
        .start = memtype_seq_start,
        .next  = memtype_seq_next,
        .stop  = memtype_seq_stop,
        .show  = memtype_seq_show,
};

static int memtype_seq_open(struct inode *inode, struct file *file)
{
        return seq_open(file, &memtype_seq_ops);
}

static const struct file_operations memtype_fops = {
        .open    = memtype_seq_open,
        .read    = seq_read,
        .llseek  = seq_lseek,
        .release = seq_release,
};

static int __init pat_memtype_list_init(void)
{
        debugfs_create_file("pat_memtype_list", S_IRUSR, arch_debugfs_dir,
                                NULL, &memtype_fops);
        return 0;
}

late_initcall(pat_memtype_list_init);

#endif /* CONFIG_DEBUG_FS && CONFIG_X86_PAT */