Merge tag 'actions-drivers-for-4.13' of git://git.kernel.org/pub/scm/linux/kernel...

[mirror_ubuntu-artful-kernel.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/ioport.h>
#include <linux/kernel.h>
#include <linux/pfn_t.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/api.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"
#include "mm_internal.h"

#undef pr_fmt
#define pr_fmt(fmt) "" fmt

static bool boot_cpu_done;

static int __read_mostly __pat_enabled = IS_ENABLED(CONFIG_X86_PAT);
static void init_cache_modes(void);

void pat_disable(const char *reason)
{
        if (!__pat_enabled)
                return;

        if (boot_cpu_done) {
                WARN_ONCE(1, "x86/PAT: PAT cannot be disabled after initialization\n");
                return;
        }

        __pat_enabled = 0;
        pr_info("x86/PAT: %s\n", reason);

        init_cache_modes();
}

static int __init nopat(char *str)
{
        pat_disable("PAT support disabled.");
        return 0;
}
early_param("nopat", nopat);

static bool __read_mostly __pat_initialized = false;

bool pat_enabled(void)
{
        return __pat_initialized;
}
EXPORT_SYMBOL_GPL(pat_enabled);

int pat_debug_enable;

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

#ifdef CONFIG_X86_PAT
/*
 * X86 PAT uses page flags arch_1 and uncached together to keep track of
 * memory type of pages that have backing page struct.
 *
 * X86 PAT supports 4 different memory types:
 *  - _PAGE_CACHE_MODE_WB
 *  - _PAGE_CACHE_MODE_WC
 *  - _PAGE_CACHE_MODE_UC_MINUS
 *  - _PAGE_CACHE_MODE_WT
 *
 * _PAGE_CACHE_MODE_WB is the default type.
 */

#define _PGMT_WB                0
#define _PGMT_WC                (1UL << PG_arch_1)
#define _PGMT_UC_MINUS          (1UL << PG_uncached)
#define _PGMT_WT                (1UL << PG_uncached | 1UL << PG_arch_1)
#define _PGMT_MASK              (1UL << PG_uncached | 1UL << PG_arch_1)
#define _PGMT_CLEAR_MASK        (~_PGMT_MASK)

static inline enum page_cache_mode get_page_memtype(struct page *pg)
{
        unsigned long pg_flags = pg->flags & _PGMT_MASK;

        if (pg_flags == _PGMT_WB)
                return _PAGE_CACHE_MODE_WB;
        else if (pg_flags == _PGMT_WC)
                return _PAGE_CACHE_MODE_WC;
        else if (pg_flags == _PGMT_UC_MINUS)
                return _PAGE_CACHE_MODE_UC_MINUS;
        else
                return _PAGE_CACHE_MODE_WT;
}

static inline void set_page_memtype(struct page *pg,
                                    enum page_cache_mode memtype)
{
        unsigned long memtype_flags;
        unsigned long old_flags;
        unsigned long new_flags;

        switch (memtype) {
        case _PAGE_CACHE_MODE_WC:
                memtype_flags = _PGMT_WC;
                break;
        case _PAGE_CACHE_MODE_UC_MINUS:
                memtype_flags = _PGMT_UC_MINUS;
                break;
        case _PAGE_CACHE_MODE_WT:
                memtype_flags = _PGMT_WT;
                break;
        case _PAGE_CACHE_MODE_WB:
        default:
                memtype_flags = _PGMT_WB;
                break;
        }

        do {
                old_flags = pg->flags;
                new_flags = (old_flags & _PGMT_CLEAR_MASK) | memtype_flags;
        } while (cmpxchg(&pg->flags, old_flags, new_flags) != old_flags);
}
#else
static inline enum page_cache_mode get_page_memtype(struct page *pg)
{
        return -1;
}
static inline void set_page_memtype(struct page *pg,
                                    enum page_cache_mode memtype)
{
}
#endif

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 overridden by MTRR */
};

#define CM(c) (_PAGE_CACHE_MODE_ ## c)

static enum page_cache_mode pat_get_cache_mode(unsigned pat_val, char *msg)
{
        enum page_cache_mode cache;
        char *cache_mode;

        switch (pat_val) {
        case PAT_UC:       cache = CM(UC);       cache_mode = "UC  "; break;
        case PAT_WC:       cache = CM(WC);       cache_mode = "WC  "; break;
        case PAT_WT:       cache = CM(WT);       cache_mode = "WT  "; break;
        case PAT_WP:       cache = CM(WP);       cache_mode = "WP  "; break;
        case PAT_WB:       cache = CM(WB);       cache_mode = "WB  "; break;
        case PAT_UC_MINUS: cache = CM(UC_MINUS); cache_mode = "UC- "; break;
        default:           cache = CM(WB);       cache_mode = "WB  "; break;
        }

        memcpy(msg, cache_mode, 4);

        return cache;
}

#undef CM

/*
 * Update the cache mode to pgprot translation tables according to PAT
 * configuration.
 * Using lower indices is preferred, so we start with highest index.
 */
static void __init_cache_modes(u64 pat)
{
        enum page_cache_mode cache;
        char pat_msg[33];
        int i;

        pat_msg[32] = 0;
        for (i = 7; i >= 0; i--) {
                cache = pat_get_cache_mode((pat >> (i * 8)) & 7,
                                           pat_msg + 4 * i);
                update_cache_mode_entry(i, cache);
        }
        pr_info("x86/PAT: Configuration [0-7]: %s\n", pat_msg);
}

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

static void pat_bsp_init(u64 pat)
{
        u64 tmp_pat;

        if (!boot_cpu_has(X86_FEATURE_PAT)) {
                pat_disable("PAT not supported by CPU.");
                return;
        }

        rdmsrl(MSR_IA32_CR_PAT, tmp_pat);
        if (!tmp_pat) {
                pat_disable("PAT MSR is 0, disabled.");
                return;
        }

        wrmsrl(MSR_IA32_CR_PAT, pat);
        __pat_initialized = true;

        __init_cache_modes(pat);
}

static void pat_ap_init(u64 pat)
{
        if (!this_cpu_has(X86_FEATURE_PAT)) {
                /*
                 * If this happens we are on a secondary CPU, but switched to
                 * PAT on the boot CPU. We have no way to undo PAT.
                 */
                panic("x86/PAT: PAT enabled, but not supported by secondary CPU\n");
        }

        wrmsrl(MSR_IA32_CR_PAT, pat);
}

static void init_cache_modes(void)
{
        u64 pat = 0;
        static int init_cm_done;

        if (init_cm_done)
                return;

        if (boot_cpu_has(X86_FEATURE_PAT)) {
                /*
                 * CPU supports PAT. Set PAT table to be consistent with
                 * PAT MSR. This case supports "nopat" boot option, and
                 * virtual machine environments which support PAT without
                 * MTRRs. In specific, Xen has unique setup to PAT MSR.
                 *
                 * If PAT MSR returns 0, it is considered invalid and emulates
                 * as No PAT.
                 */
                rdmsrl(MSR_IA32_CR_PAT, pat);
        }

        if (!pat) {
                /*
                 * No PAT. Emulate the PAT table that corresponds to the two
                 * cache bits, PWT (Write Through) and PCD (Cache Disable).
                 * This setup is also the same as the BIOS default setup.
                 *
                 * PTE encoding:
                 *
                 *       PCD
                 *       |PWT  PAT
                 *       ||    slot
                 *       00    0    WB : _PAGE_CACHE_MODE_WB
                 *       01    1    WT : _PAGE_CACHE_MODE_WT
                 *       10    2    UC-: _PAGE_CACHE_MODE_UC_MINUS
                 *       11    3    UC : _PAGE_CACHE_MODE_UC
                 *
                 * NOTE: When WC or WP is used, it is redirected to UC- per
                 * the default setup in __cachemode2pte_tbl[].
                 */
                pat = PAT(0, WB) | PAT(1, WT) | PAT(2, UC_MINUS) | PAT(3, UC) |
                      PAT(4, WB) | PAT(5, WT) | PAT(6, UC_MINUS) | PAT(7, UC);
        }

        __init_cache_modes(pat);

        init_cm_done = 1;
}

/**
 * pat_init - Initialize PAT MSR and PAT table
 *
 * This function initializes PAT MSR and PAT table with an OS-defined value
 * to enable additional cache attributes, WC and WT.
 *
 * This function must be called on all CPUs using the specific sequence of
 * operations defined in Intel SDM. mtrr_rendezvous_handler() provides this
 * procedure for PAT.
 */
void pat_init(void)
{
        u64 pat;
        struct cpuinfo_x86 *c = &boot_cpu_data;

        if (!__pat_enabled) {
                init_cache_modes();
                return;
        }

        if ((c->x86_vendor == X86_VENDOR_INTEL) &&
            (((c->x86 == 0x6) && (c->x86_model <= 0xd)) ||
             ((c->x86 == 0xf) && (c->x86_model <= 0x6)))) {
                /*
                 * PAT support with the lower four entries. Intel Pentium 2,
                 * 3, M, and 4 are affected by PAT errata, which makes the
                 * upper four entries unusable. To be on the safe side, we don't
                 * use those.
                 *
                 *  PTE encoding:
                 *      PAT
                 *      |PCD
                 *      ||PWT  PAT
                 *      |||    slot
                 *      000    0    WB : _PAGE_CACHE_MODE_WB
                 *      001    1    WC : _PAGE_CACHE_MODE_WC
                 *      010    2    UC-: _PAGE_CACHE_MODE_UC_MINUS
                 *      011    3    UC : _PAGE_CACHE_MODE_UC
                 * PAT bit unused
                 *
                 * NOTE: When WT or WP is used, it is redirected to UC- per
                 * the default setup in __cachemode2pte_tbl[].
                 */
                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);
        } else {
                /*
                 * Full PAT support.  We put WT in slot 7 to improve
                 * robustness in the presence of errata that might cause
                 * the high PAT bit to be ignored.  This way, a buggy slot 7
                 * access will hit slot 3, and slot 3 is UC, so at worst
                 * we lose performance without causing a correctness issue.
                 * Pentium 4 erratum N46 is an example for such an erratum,
                 * although we try not to use PAT at all on affected CPUs.
                 *
                 *  PTE encoding:
                 *      PAT
                 *      |PCD
                 *      ||PWT  PAT
                 *      |||    slot
                 *      000    0    WB : _PAGE_CACHE_MODE_WB
                 *      001    1    WC : _PAGE_CACHE_MODE_WC
                 *      010    2    UC-: _PAGE_CACHE_MODE_UC_MINUS
                 *      011    3    UC : _PAGE_CACHE_MODE_UC
                 *      100    4    WB : Reserved
                 *      101    5    WC : Reserved
                 *      110    6    UC-: Reserved
                 *      111    7    WT : _PAGE_CACHE_MODE_WT
                 *
                 * The reserved slots are unused, but mapped to their
                 * corresponding types in the presence of PAT errata.
                 */
                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, WT);
        }

        if (!boot_cpu_done) {
                pat_bsp_init(pat);
                boot_cpu_done = true;
        } else {
                pat_ap_init(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,
                                     enum page_cache_mode req_type)
{
        /*
         * Look for MTRR hint to get the effective type in case where PAT
         * request is for WB.
         */
        if (req_type == _PAGE_CACHE_MODE_WB) {
                u8 mtrr_type, uniform;

                mtrr_type = mtrr_type_lookup(start, end, &uniform);
                if (mtrr_type != MTRR_TYPE_WRBACK)
                        return _PAGE_CACHE_MODE_UC_MINUS;

                return _PAGE_CACHE_MODE_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.
 * The page flags are limited to four types, WB (default), WC, WT and UC-.
 * WP request fails with -EINVAL, and UC gets redirected to UC-.  Setting
 * a new memory type is only allowed for a page mapped with the default WB
 * type.
 *
 * Here we do two passes:
 * - 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,
                                  enum page_cache_mode req_type,
                                  enum page_cache_mode *new_type)
{
        struct page *page;
        u64 pfn;

        if (req_type == _PAGE_CACHE_MODE_WP) {
                if (new_type)
                        *new_type = _PAGE_CACHE_MODE_UC_MINUS;
                return -EINVAL;
        }

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

        for (pfn = (start >> PAGE_SHIFT); pfn < (end >> PAGE_SHIFT); ++pfn) {
                enum page_cache_mode type;

                page = pfn_to_page(pfn);
                type = get_page_memtype(page);
                if (type != _PAGE_CACHE_MODE_WB) {
                        pr_info("x86/PAT: reserve_ram_pages_type failed [mem %#010Lx-%#010Lx], track 0x%x, req 0x%x\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, _PAGE_CACHE_MODE_WB);
        }
        return 0;
}

/*
 * req_type typically has one of the:
 * - _PAGE_CACHE_MODE_WB
 * - _PAGE_CACHE_MODE_WC
 * - _PAGE_CACHE_MODE_UC_MINUS
 * - _PAGE_CACHE_MODE_UC
 * - _PAGE_CACHE_MODE_WT
 *
 * 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, enum page_cache_mode req_type,
                    enum page_cache_mode *new_type)
{
        struct memtype *new;
        enum page_cache_mode 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)
                        *new_type = req_type;
                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_MODE_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);

        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) {
                pr_info("x86/PAT: 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 (IS_ERR(entry)) {
                pr_info("x86/PAT: %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_MODE_WB, _PAGE_CACHE_MODE_WC, _PAGE_CACHE_MODE_UC_MINUS
 * or _PAGE_CACHE_MODE_WT.
 */
static enum page_cache_mode lookup_memtype(u64 paddr)
{
        enum page_cache_mode rettype = _PAGE_CACHE_MODE_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);
                return get_page_memtype(page);
        }

        spin_lock(&memtype_lock);

        entry = rbt_memtype_lookup(paddr);
        if (entry != NULL)
                rettype = entry->type;
        else
                rettype = _PAGE_CACHE_MODE_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,
                        enum page_cache_mode *type)
{
        resource_size_t size = end - start;
        enum page_cache_mode req_type = *type;
        enum page_cache_mode 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);
}

int arch_io_reserve_memtype_wc(resource_size_t start, resource_size_t size)
{
        enum page_cache_mode type = _PAGE_CACHE_MODE_WC;

        return io_reserve_memtype(start, start + size, &type);
}
EXPORT_SYMBOL(arch_io_reserve_memtype_wc);

void arch_io_free_memtype_wc(resource_size_t start, resource_size_t size)
{
        io_free_memtype(start, start + size);
}
EXPORT_SYMBOL(arch_io_free_memtype_wc);

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))
                        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)
{
        enum page_cache_mode pcm = _PAGE_CACHE_MODE_WB;

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

        if (file->f_flags & O_DSYNC)
                pcm = _PAGE_CACHE_MODE_UC_MINUS;

        *vma_prot = __pgprot((pgprot_val(*vma_prot) & ~_PAGE_CACHE_MASK) |
                             cachemode2protval(pcm));
        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,
                            enum page_cache_mode pcm)
{
        unsigned long id_sz;

        if (base > __pa(high_memory-1))
                return 0;

        /*
         * some areas in the middle of the kernel identity range
         * are not mapped, like the PCI space.
         */
        if (!page_is_ram(base >> PAGE_SHIFT))
                return 0;

        id_sz = (__pa(high_memory-1) <= base + size) ?
                                __pa(high_memory) - base :
                                size;

        if (ioremap_change_attr((unsigned long)__va(base), id_sz, pcm) < 0) {
                pr_info("x86/PAT: %s:%d ioremap_change_attr failed %s for [mem %#010Lx-%#010Lx]\n",
                        current->comm, current->pid,
                        cattr_name(pcm),
                        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;
        enum page_cache_mode want_pcm = pgprot2cachemode(*vma_prot);
        enum page_cache_mode pcm = want_pcm;

        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;

                pcm = lookup_memtype(paddr);
                if (want_pcm != pcm) {
                        pr_warn("x86/PAT: %s:%d map pfn RAM range req %s for [mem %#010Lx-%#010Lx], got %s\n",
                                current->comm, current->pid,
                                cattr_name(want_pcm),
                                (unsigned long long)paddr,
                                (unsigned long long)(paddr + size - 1),
                                cattr_name(pcm));
                        *vma_prot = __pgprot((pgprot_val(*vma_prot) &
                                             (~_PAGE_CACHE_MASK)) |
                                             cachemode2protval(pcm));
                }
                return 0;
        }

        ret = reserve_memtype(paddr, paddr + size, want_pcm, &pcm);
        if (ret)
                return ret;

        if (pcm != want_pcm) {
                if (strict_prot ||
                    !is_new_memtype_allowed(paddr, size, want_pcm, pcm)) {
                        free_memtype(paddr, paddr + size);
                        pr_err("x86/PAT: %s:%d map pfn expected mapping type %s for [mem %#010Lx-%#010Lx], got %s\n",
                               current->comm, current->pid,
                               cattr_name(want_pcm),
                               (unsigned long long)paddr,
                               (unsigned long long)(paddr + size - 1),
                               cattr_name(pcm));
                        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)) |
                                     cachemode2protval(pcm));
        }

        if (kernel_map_sync_memtype(paddr, size, pcm) < 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, or no vma is provided,
 * reserve the entire pfn + size 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;
        enum page_cache_mode pcm;

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

                ret = reserve_pfn_range(paddr, size, prot, 0);
                if (ret == 0 && vma)
                        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.
         */
        pcm = lookup_memtype(paddr);

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

        *prot = __pgprot((pgprot_val(*prot) & (~_PAGE_CACHE_MASK)) |
                         cachemode2protval(pcm));

        return 0;
}

void track_pfn_insert(struct vm_area_struct *vma, pgprot_t *prot, pfn_t pfn)
{
        enum page_cache_mode pcm;

        if (!pat_enabled())
                return;

        /* Set prot based on lookup */
        pcm = lookup_memtype(pfn_t_to_phys(pfn));
        *prot = __pgprot((pgprot_val(*prot) & (~_PAGE_CACHE_MASK)) |
                         cachemode2protval(pcm));
}

/*
 * 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 && !(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);
        if (vma)
                vma->vm_flags &= ~VM_PAT;
}

/*
 * untrack_pfn_moved is called, while mremapping a pfnmap for a new region,
 * with the old vma after its pfnmap page table has been removed.  The new
 * vma has a new pfnmap to the same pfn & cache type with VM_PAT set.
 */
void untrack_pfn_moved(struct vm_area_struct *vma)
{
        vma->vm_flags &= ~VM_PAT;
}

pgprot_t pgprot_writecombine(pgprot_t prot)
{
        return __pgprot(pgprot_val(prot) |
                                cachemode2protval(_PAGE_CACHE_MODE_WC));
}
EXPORT_SYMBOL_GPL(pgprot_writecombine);

pgprot_t pgprot_writethrough(pgprot_t prot)
{
        return __pgprot(pgprot_val(prot) |
                                cachemode2protval(_PAGE_CACHE_MODE_WT));
}
EXPORT_SYMBOL_GPL(pgprot_writethrough);

#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_puts(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 */