pat.c

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/*
 * Handle caching attributes in page tables (PAT)
 *
 * Authors: Venkatesh Pallipadi <[email protected]>
 *          Suresh B Siddha <[email protected]>
 *
 * 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/slab.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/x86_init.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>

#include "pat_internal.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


int pat_debug_enable;

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

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;
    bool boot_cpu = !boot_pat_state;

    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);

    if (boot_cpu)
        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 DEFINE_SPINLOCK(memtype_lock);   /* protects memtype accesses */

/*
 * 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;
}

struct pagerange_state {
    unsigned long       cur_pfn;
    int         ram;
    int         not_ram;
};

static int
pagerange_is_ram_callback(unsigned long initial_pfn, unsigned long total_nr_pages, void *arg)
{
    struct pagerange_state *state = arg;

    state->not_ram  |= initial_pfn > state->cur_pfn;
    state->ram  |= total_nr_pages > 0;
    state->cur_pfn   = initial_pfn + total_nr_pages;

    return state->ram && state->not_ram;
}

static int pat_pagerange_is_ram(resource_size_t start, resource_size_t end)
{
    int ret = 0;
    unsigned long start_pfn = start >> PAGE_SHIFT;
    unsigned long end_pfn = (end + PAGE_SIZE - 1) >> PAGE_SHIFT;
    struct pagerange_state state = {start_pfn, 0, 0};

    /*
     * 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 (start_pfn < ISA_END_ADDRESS >> PAGE_SHIFT)
        start_pfn = ISA_END_ADDRESS >> PAGE_SHIFT;

    if (start_pfn < end_pfn) {
        ret = walk_system_ram_range(start_pfn, end_pfn - start_pfn,
                &state, pagerange_is_ram_callback);
    }

    return (ret > 0) ? -1 : (state.ram ? 1 : 0);
}

/*
 * For RAM pages, we use page flags to mark the pages with appropriate type.
 * Here we do two pass:
 * - Find the memtype of all the pages in the range, look for any conflicts
 * - In case of no conflicts, set the new memtype for pages in the range
 */
static int reserve_ram_pages_type(u64 start, u64 end, unsigned long req_type,
                  unsigned long *new_type)
{
    struct page *page;
    u64 pfn;

    if (req_type == _PAGE_CACHE_UC) {
        /* We do not support strong UC */
        WARN_ON_ONCE(1);
        req_type = _PAGE_CACHE_UC_MINUS;
    }

    for (pfn = (start >> PAGE_SHIFT); pfn < (end >> PAGE_SHIFT); ++pfn) {
        unsigned long type;

        page = pfn_to_page(pfn);
        type = get_page_memtype(page);
        if (type != -1) {
            printk(KERN_INFO "reserve_ram_pages_type failed [mem %#010Lx-%#010Lx], track 0x%lx, req 0x%lx\n",
                start, end - 1, type, req_type);
            if (new_type)
                *new_type = type;

            return -EBUSY;
        }
    }

    if (new_type)
        *new_type = req_type;

    for (pfn = (start >> PAGE_SHIFT); pfn < (end >> PAGE_SHIFT); ++pfn) {
        page = pfn_to_page(pfn);
        set_page_memtype(page, req_type);
    }
    return 0;
}

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

    for (pfn = (start >> PAGE_SHIFT); pfn < (end >> PAGE_SHIFT); ++pfn) {
        page = pfn_to_page(pfn);
        set_page_memtype(page, -1);
    }
    return 0;
}

/*
 * req_type typically has one of the:
 * - _PAGE_CACHE_WB
 * - _PAGE_CACHE_WC
 * - _PAGE_CACHE_UC_MINUS
 * - _PAGE_CACHE_UC
 *
 * 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;
    unsigned long actual_type;
    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 == _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 (x86_platform.is_untracked_pat_range(start, end)) {
        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) {

        err = reserve_ram_pages_type(start, end, req_type, new_type);

        return err;
    } else if (is_range_ram < 0) {
        return -EINVAL;
    }

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

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

    spin_lock(&memtype_lock);

    err = rbt_memtype_check_insert(new, new_type);
    if (err) {
        printk(KERN_INFO "reserve_memtype failed [mem %#010Lx-%#010Lx], track %s, req %s\n",
               start, end - 1,
               cattr_name(new->type), cattr_name(req_type));
        kfree(new);
        spin_unlock(&memtype_lock);

        return err;
    }

    spin_unlock(&memtype_lock);

    dprintk("reserve_memtype added [mem %#010Lx-%#010Lx], track %s, req %s, ret %s\n",
        start, end - 1, cattr_name(new->type), cattr_name(req_type),
        new_type ? cattr_name(*new_type) : "-");

    return err;
}

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

    if (!pat_enabled)
        return 0;

    /* Low ISA region is always mapped WB. No need to track */
    if (x86_platform.is_untracked_pat_range(start, end))
        return 0;

    is_range_ram = pat_pagerange_is_ram(start, end);
    if (is_range_ram == 1) {

        err = free_ram_pages_type(start, end);

        return err;
    } else if (is_range_ram < 0) {
        return -EINVAL;
    }

    spin_lock(&memtype_lock);
    entry = rbt_memtype_erase(start, end);
    spin_unlock(&memtype_lock);

    if (!entry) {
        printk(KERN_INFO "%s:%d freeing invalid memtype [mem %#010Lx-%#010Lx]\n",
               current->comm, current->pid, start, end - 1);
        return -EINVAL;
    }

    kfree(entry);

    dprintk("free_memtype request [mem %#010Lx-%#010Lx]\n", start, end - 1);

    return 0;
}


static unsigned long lookup_memtype(u64 paddr)
{
    int rettype = _PAGE_CACHE_WB;
    struct memtype *entry;

    if (x86_platform.is_untracked_pat_range(paddr, paddr + PAGE_SIZE))
        return rettype;

    if (pat_pagerange_is_ram(paddr, paddr + PAGE_SIZE)) {
        struct page *page;
        page = pfn_to_page(paddr >> PAGE_SHIFT);
        rettype = get_page_memtype(page);
        /*
         * -1 from get_page_memtype() implies RAM page is in its
         * default state and not reserved, and hence of type WB
         */
        if (rettype == -1)
            rettype = _PAGE_CACHE_WB;

        return rettype;
    }

    spin_lock(&memtype_lock);

    entry = rbt_memtype_lookup(paddr);
    if (entry != NULL)
        rettype = entry->type;
    else
        rettype = _PAGE_CACHE_UC_MINUS;

    spin_unlock(&memtype_lock);
    return rettype;
}

int io_reserve_memtype(resource_size_t start, resource_size_t end,
            unsigned long *type)
{
    resource_size_t size = end - start;
    unsigned long req_type = *type;
    unsigned long new_type;
    int ret;

    WARN_ON_ONCE(iomem_map_sanity_check(start, size));

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

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

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

    *type = new_type;
    return 0;

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

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 [mem %#010Lx-%#010Lx]\n",
                current->comm, from, to - 1);
            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_DSYNC)
        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 [mem %#010Lx-%#010Lx]\n",
            current->comm, current->pid,
            cattr_name(flags),
            base, (unsigned long long)(base + size-1));
        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() for RAM pages. We do not refcount to keep
     * track of number of mappings of RAM pages. We can assert that
     * the type requested matches the type of first page in the range.
     */
    if (is_ram) {
        if (!pat_enabled)
            return 0;

        flags = lookup_memtype(paddr);
        if (want_flags != flags) {
            printk(KERN_WARNING "%s:%d map pfn RAM range req %s for [mem %#010Lx-%#010Lx], got %s\n",
                current->comm, current->pid,
                cattr_name(want_flags),
                (unsigned long long)paddr,
                (unsigned long long)(paddr + size - 1),
                cattr_name(flags));
            *vma_prot = __pgprot((pgprot_val(*vma_prot) &
                          (~_PAGE_CACHE_MASK)) |
                         flags);
        }
        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(paddr, size, want_flags, flags)) {
            free_memtype(paddr, paddr + size);
            printk(KERN_ERR "%s:%d map pfn expected mapping type %s"
                " for [mem %#010Lx-%#010Lx], got %s\n",
                current->comm, current->pid,
                cattr_name(want_flags),
                (unsigned long long)paddr,
                (unsigned long long)(paddr + size - 1),
                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_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_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;

    if (vma->vm_flags & VM_PAT) {
        /*
         * 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;
}

/*
 * 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_remap(struct vm_area_struct *vma, pgprot_t *prot,
            unsigned long pfn, unsigned long addr, unsigned long size)
{
    resource_size_t paddr = (resource_size_t)pfn << PAGE_SHIFT;
    unsigned long flags;

    /* reserve the whole chunk starting from paddr */
    if (addr == vma->vm_start && size == (vma->vm_end - vma->vm_start)) {
        int ret;

        ret = reserve_pfn_range(paddr, size, prot, 0);
        if (!ret)
            vma->vm_flags |= VM_PAT;
        return ret;
    }

    if (!pat_enabled)
        return 0;

    /*
     * For anything smaller than the vma size we set prot based on the
     * lookup.
     */
    flags = lookup_memtype(paddr);

    /* Check memtype for the remaining pages */
    while (size > PAGE_SIZE) {
        size -= PAGE_SIZE;
        paddr += PAGE_SIZE;
        if (flags != lookup_memtype(paddr))
            return -EINVAL;
    }

    *prot = __pgprot((pgprot_val(vma->vm_page_prot) & (~_PAGE_CACHE_MASK)) |
             flags);

    return 0;
}

int track_pfn_insert(struct vm_area_struct *vma, pgprot_t *prot,
             unsigned long pfn)
{
    unsigned long flags;

    if (!pat_enabled)
        return 0;

    /* Set prot based on lookup */
    flags = lookup_memtype((resource_size_t)pfn << PAGE_SHIFT);
    *prot = __pgprot((pgprot_val(vma->vm_page_prot) & (~_PAGE_CACHE_MASK)) |
             flags);

    return 0;
}

/*
 * untrack_pfn 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 pfn, size are zero).
 */
void untrack_pfn(struct vm_area_struct *vma, unsigned long pfn,
         unsigned long size)
{
    resource_size_t paddr;
    unsigned long prot;

    if (!(vma->vm_flags & VM_PAT))
        return;

    /* free the chunk starting from pfn or the whole chunk */
    paddr = (resource_size_t)pfn << PAGE_SHIFT;
    if (!paddr && !size) {
        if (follow_phys(vma, vma->vm_start, 0, &prot, &paddr)) {
            WARN_ON_ONCE(1);
            return;
        }

        size = vma->vm_end - vma->vm_start;
    }
    free_pfn_range(paddr, size);
    vma->vm_flags &= ~VM_PAT;
}

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)

static struct memtype *memtype_get_idx(loff_t pos)
{
    struct memtype *print_entry;
    int ret;

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

    spin_lock(&memtype_lock);
    ret = rbt_memtype_copy_nth_element(print_entry, pos);
    spin_unlock(&memtype_lock);

    if (!ret) {
        return print_entry;
    } else {
        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 const 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)
{
    if (pat_enabled) {
        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 */