Linux 3.8-rc7

[cris-mirror.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/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;
}


/**
 * lookup_memtype - Looksup the memory type for a physical address
 * @paddr: physical address of which memory type needs to be looked up
 *
 * Only to be called when PAT is enabled
 *
 * Returns _PAGE_CACHE_WB, _PAGE_CACHE_WC, _PAGE_CACHE_UC_MINUS or
 * _PAGE_CACHE_UC
 */
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;
}

/**
 * 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)
{
        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;
}

/**
 * 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 [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 */