Merge branch 'core/percpu' into stackprotector

[deliverable/linux.git] / 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/gfp.h>
#include <linux/mm.h>
#include <linux/fs.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;

void __cpuinit pat_disable(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);
#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;

        /* Paranoia check. */
        if (!cpu_has_pat && boot_pat_state) {
                /*
                 * 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.
 *
 * Currently the data structure is a list because the number of mappings
 * are expected to be relatively small. If this should be a problem
 * it could be changed to a rbtree or similar.
 *
 * memtype_lock protects the whole list.
 */

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

static LIST_HEAD(memtype_list);
static DEFINE_SPINLOCK(memtype_lock);   /* protects memtype list */

/*
 * 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_UNCACHABLE)
                        return _PAGE_CACHE_UC;
                if (mtrr_type == MTRR_TYPE_WRCOMB)
                        return _PAGE_CACHE_WC;
        }

        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 struct memtype *cached_entry;
static u64 cached_start;

/*
 * 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
                                *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;
        }

        if (req_type == -1) {
                /*
                 * 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.
                 */
                u8 mtrr_type = mtrr_type_lookup(start, end);

                if (mtrr_type == MTRR_TYPE_WRBACK)
                        actual_type = _PAGE_CACHE_WB;
                else
                        actual_type = _PAGE_CACHE_UC_MINUS;
        } else {
                actual_type = pat_x_mtrr_type(start, end,
                                              req_type & _PAGE_CACHE_MASK);
        }

        /*
         * For legacy reasons, some parts of the physical address range in the
         * legacy 1MB region is treated as non-RAM (even when listed as RAM in
         * the e820 tables).  So we will track the memory attributes of this
         * legacy 1MB region using the linear memtype_list always.
         */
        if (end >= ISA_END_ADDRESS) {
                is_range_ram = 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;

        if (new_type)
                *new_type = actual_type;

        spin_lock(&memtype_lock);

        if (cached_entry && start >= cached_start)
                entry = cached_entry;
        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;
                        cached_entry = list_entry(where, struct memtype, nd);
                        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;
                                cached_entry = list_entry(where,
                                                        struct memtype, nd);
                        }
                        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);
                                cached_entry = list_entry(entry->nd.prev,
                                                        struct memtype, nd);

                                /*
                                 * 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;
        }

        cached_start = start;

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

        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;
        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;

        /*
         * For legacy reasons, some parts of the physical address range in the
         * legacy 1MB region is treated as non-RAM (even when listed as RAM in
         * the e820 tables).  So we will track the memory attributes of this
         * legacy 1MB region using the linear memtype_list always.
         */
        if (end >= ISA_END_ADDRESS) {
                is_range_ram = 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);
        list_for_each_entry(entry, &memtype_list, nd) {
                if (entry->start == start && entry->end == end) {
                        if (cached_entry == entry || cached_start == start)
                                cached_entry = NULL;

                        list_del(&entry->nd);
                        kfree(entry);
                        err = 0;
                        break;
                }
        }
        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;
}


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 */

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

        if (!pat_enabled || base >= __pa(high_memory))
                return 0;

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

        ret = ioremap_change_attr((unsigned long)__va(base), id_sz, flags);
        /*
         * -EFAULT return means that the addr was not valid and did not have
         * any identity mapping. That case is a success for
         * kernel_map_sync_memtype.
         */
        if (ret == -EFAULT)
                ret = 0;

        return ret;
}

int phys_mem_access_prot_allowed(struct file *file, unsigned long pfn,
                                unsigned long size, pgprot_t *vma_prot)
{
        u64 offset = ((u64) pfn) << PAGE_SHIFT;
        unsigned long flags = -1;
        int retval;

        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

        /*
         * With O_SYNC, we can only take UC_MINUS mapping. Fail if we cannot.
         *
         * Without O_SYNC, we want to get
         * - WB for WB-able memory and no other conflicting mappings
         * - UC_MINUS for non-WB-able memory with no other conflicting mappings
         * - Inherit from confliting mappings otherwise
         */
        if (flags != -1) {
                retval = reserve_memtype(offset, offset + size, flags, NULL);
        } else {
                retval = reserve_memtype(offset, offset + size, -1, &flags);
        }

        if (retval < 0)
                return 0;

        if (kernel_map_sync_memtype(offset, size, flags)) {
                free_memtype(offset, offset + size);
                printk(KERN_INFO
                "%s:%d /dev/mem ioremap_change_attr failed %s for %Lx-%Lx\n",
                        current->comm, current->pid,
                        cattr_name(flags),
                        offset, (unsigned long long)(offset + size));
                return 0;
        }

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

void map_devmem(unsigned long pfn, unsigned long size, pgprot_t vma_prot)
{
        unsigned long want_flags = (pgprot_val(vma_prot) & _PAGE_CACHE_MASK);
        u64 addr = (u64)pfn << PAGE_SHIFT;
        unsigned long flags;

        reserve_memtype(addr, addr + size, want_flags, &flags);
        if (flags != want_flags) {
                printk(KERN_INFO
                "%s:%d /dev/mem expected mapping type %s for %Lx-%Lx, got %s\n",
                        current->comm, current->pid,
                        cattr_name(want_flags),
                        addr, (unsigned long long)(addr + size),
                        cattr_name(flags));
        }
}

void unmap_devmem(unsigned long pfn, unsigned long size, pgprot_t vma_prot)
{
        u64 addr = (u64)pfn << PAGE_SHIFT;

        free_memtype(addr, addr + size);
}

/*
 * 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 flags;
        unsigned long want_flags = (pgprot_val(*vma_prot) & _PAGE_CACHE_MASK);

        is_ram = pagerange_is_ram(paddr, paddr + size);

        if (is_ram != 0) {
                /*
                 * For mapping RAM pages, drivers need to call
                 * set_memory_[uc|wc|wb] directly, for reserve and free, before
                 * setting up the PTE.
                 */
                WARN_ON_ONCE(1);
                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)) {
                free_memtype(paddr, paddr + size);
                printk(KERN_ERR
                        "%s:%d reserve_pfn_range ioremap_change_attr failed %s "
                        "for %Lx-%Lx\n",
                        current->comm, current->pid,
                        cattr_name(flags),
                        (unsigned long long)paddr,
                        (unsigned long long)(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 = 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.
 * Otherwise, we reserve the entire vma range, my ging through the PTEs page
 * by page to get physical address and protection.
 */
int track_pfn_vma_copy(struct vm_area_struct *vma)
{
        int retval = 0;
        unsigned long i, j;
        resource_size_t paddr;
        unsigned long prot;
        unsigned long vma_start = vma->vm_start;
        unsigned long vma_end = vma->vm_end;
        unsigned long vma_size = vma_end - vma_start;
        pgprot_t pgprot;

        if (!pat_enabled)
                return 0;

        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_start, 0, &prot, &paddr)) {
                        WARN_ON_ONCE(1);
                        return -EINVAL;
                }
                pgprot = __pgprot(prot);
                return reserve_pfn_range(paddr, vma_size, &pgprot, 1);
        }

        /* reserve entire vma page by page, using pfn and prot from pte */
        for (i = 0; i < vma_size; i += PAGE_SIZE) {
                if (follow_phys(vma, vma_start + i, 0, &prot, &paddr))
                        continue;

                pgprot = __pgprot(prot);
                retval = reserve_pfn_range(paddr, PAGE_SIZE, &pgprot, 1);
                if (retval)
                        goto cleanup_ret;
        }
        return 0;

cleanup_ret:
        /* Reserve error: Cleanup partial reservation and return error */
        for (j = 0; j < i; j += PAGE_SIZE) {
                if (follow_phys(vma, vma_start + j, 0, &prot, &paddr))
                        continue;

                free_pfn_range(paddr, PAGE_SIZE);
        }

        return retval;
}

/*
 * 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.
 * Otherwise, we look t the pfn and size and reserve only the specified range
 * page by page.
 *
 * Note that this function can be called with caller trying to map only a
 * subrange/page inside the vma.
 */
int track_pfn_vma_new(struct vm_area_struct *vma, pgprot_t *prot,
                        unsigned long pfn, unsigned long size)
{
        int retval = 0;
        unsigned long i, j;
        resource_size_t base_paddr;
        resource_size_t paddr;
        unsigned long vma_start = vma->vm_start;
        unsigned long vma_end = vma->vm_end;
        unsigned long vma_size = vma_end - vma_start;

        if (!pat_enabled)
                return 0;

        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);
        }

        /* reserve page by page using pfn and size */
        base_paddr = (resource_size_t)pfn << PAGE_SHIFT;
        for (i = 0; i < size; i += PAGE_SIZE) {
                paddr = base_paddr + i;
                retval = reserve_pfn_range(paddr, PAGE_SIZE, prot, 0);
                if (retval)
                        goto cleanup_ret;
        }
        return 0;

cleanup_ret:
        /* Reserve error: Cleanup partial reservation and return error */
        for (j = 0; j < i; j += PAGE_SIZE) {
                paddr = base_paddr + j;
                free_pfn_range(paddr, PAGE_SIZE);
        }

        return retval;
}

/*
 * 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)
{
        unsigned long i;
        resource_size_t paddr;
        unsigned long prot;
        unsigned long vma_start = vma->vm_start;
        unsigned long vma_end = vma->vm_end;
        unsigned long vma_size = vma_end - vma_start;

        if (!pat_enabled)
                return;

        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;
        }

        if (size != 0 && size != vma_size) {
                /* free page by page, using pfn and size */
                paddr = (resource_size_t)pfn << PAGE_SHIFT;
                for (i = 0; i < size; i += PAGE_SIZE) {
                        paddr = paddr + i;
                        free_pfn_range(paddr, PAGE_SIZE);
                }
        } else {
                /* free entire vma, page by page, using the pfn from pte */
                for (i = 0; i < vma_size; i += PAGE_SIZE) {
                        if (follow_phys(vma, vma_start + i, 0, &prot, &paddr))
                                continue;

                        free_pfn_range(paddr, PAGE_SIZE);
                }
        }
}

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

#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 */