x86/mm: Fix pgd_lock deadlock

[linux-2.6.git] / arch / x86 / mm / pageattr.c

/*
 * Copyright 2002 Andi Kleen, SuSE Labs.
 * Thanks to Ben LaHaise for precious feedback.
 */
#include <linux/highmem.h>
#include <linux/bootmem.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/seq_file.h>
#include <linux/debugfs.h>
#include <linux/pfn.h>
#include <linux/percpu.h>
#include <linux/gfp.h>
#include <linux/pci.h>

#include <asm/e820.h>
#include <asm/processor.h>
#include <asm/tlbflush.h>
#include <asm/sections.h>
#include <asm/setup.h>
#include <asm/uaccess.h>
#include <asm/pgalloc.h>
#include <asm/proto.h>
#include <asm/pat.h>

/*
 * The current flushing context - we pass it instead of 5 arguments:
 */
struct cpa_data {
        unsigned long   *vaddr;
        pgprot_t        mask_set;
        pgprot_t        mask_clr;
        int             numpages;
        int             flags;
        unsigned long   pfn;
        unsigned        force_split : 1;
        int             curpage;
        struct page     **pages;
};

/*
 * Serialize cpa() (for !DEBUG_PAGEALLOC which uses large identity mappings)
 * using cpa_lock. So that we don't allow any other cpu, with stale large tlb
 * entries change the page attribute in parallel to some other cpu
 * splitting a large page entry along with changing the attribute.
 */
static DEFINE_SPINLOCK(cpa_lock);

#define CPA_FLUSHTLB 1
#define CPA_ARRAY 2
#define CPA_PAGES_ARRAY 4

#ifdef CONFIG_PROC_FS
static unsigned long direct_pages_count[PG_LEVEL_NUM];

void update_page_count(int level, unsigned long pages)
{
        /* Protect against CPA */
        spin_lock(&pgd_lock);
        direct_pages_count[level] += pages;
        spin_unlock(&pgd_lock);
}

static void split_page_count(int level)
{
        direct_pages_count[level]--;
        direct_pages_count[level - 1] += PTRS_PER_PTE;
}

void arch_report_meminfo(struct seq_file *m)
{
        seq_printf(m, "DirectMap4k:    %8lu kB\n",
                        direct_pages_count[PG_LEVEL_4K] << 2);
#if defined(CONFIG_X86_64) || defined(CONFIG_X86_PAE)
        seq_printf(m, "DirectMap2M:    %8lu kB\n",
                        direct_pages_count[PG_LEVEL_2M] << 11);
#else
        seq_printf(m, "DirectMap4M:    %8lu kB\n",
                        direct_pages_count[PG_LEVEL_2M] << 12);
#endif
#ifdef CONFIG_X86_64
        if (direct_gbpages)
                seq_printf(m, "DirectMap1G:    %8lu kB\n",
                        direct_pages_count[PG_LEVEL_1G] << 20);
#endif
}
#else
static inline void split_page_count(int level) { }
#endif

#ifdef CONFIG_X86_64

static inline unsigned long highmap_start_pfn(void)
{
        return __pa(_text) >> PAGE_SHIFT;
}

static inline unsigned long highmap_end_pfn(void)
{
        return __pa(roundup(_brk_end, PMD_SIZE)) >> PAGE_SHIFT;
}

#endif

#ifdef CONFIG_DEBUG_PAGEALLOC
# define debug_pagealloc 1
#else
# define debug_pagealloc 0
#endif

static inline int
within(unsigned long addr, unsigned long start, unsigned long end)
{
        return addr >= start && addr < end;
}

/*
 * Flushing functions
 */

/**
 * clflush_cache_range - flush a cache range with clflush
 * @addr:       virtual start address
 * @size:       number of bytes to flush
 *
 * clflush is an unordered instruction which needs fencing with mfence
 * to avoid ordering issues.
 */
void clflush_cache_range(void *vaddr, unsigned int size)
{
        void *vend = vaddr + size - 1;

        mb();

        for (; vaddr < vend; vaddr += boot_cpu_data.x86_clflush_size)
                clflush(vaddr);
        /*
         * Flush any possible final partial cacheline:
         */
        clflush(vend);

        mb();
}
EXPORT_SYMBOL_GPL(clflush_cache_range);

static void __cpa_flush_all(void *arg)
{
        unsigned long cache = (unsigned long)arg;

        /*
         * Flush all to work around Errata in early athlons regarding
         * large page flushing.
         */
        __flush_tlb_all();

        if (cache && boot_cpu_data.x86 >= 4)
                wbinvd();
}

static void cpa_flush_all(unsigned long cache)
{
        BUG_ON(irqs_disabled());

        on_each_cpu(__cpa_flush_all, (void *) cache, 1);
}

static void __cpa_flush_range(void *arg)
{
        /*
         * We could optimize that further and do individual per page
         * tlb invalidates for a low number of pages. Caveat: we must
         * flush the high aliases on 64bit as well.
         */
        __flush_tlb_all();
}

static void cpa_flush_range(unsigned long start, int numpages, int cache)
{
        unsigned int i, level;
        unsigned long addr;

        BUG_ON(irqs_disabled());
        WARN_ON(PAGE_ALIGN(start) != start);

        on_each_cpu(__cpa_flush_range, NULL, 1);

        if (!cache)
                return;

        /*
         * We only need to flush on one CPU,
         * clflush is a MESI-coherent instruction that
         * will cause all other CPUs to flush the same
         * cachelines:
         */
        for (i = 0, addr = start; i < numpages; i++, addr += PAGE_SIZE) {
                pte_t *pte = lookup_address(addr, &level);

                /*
                 * Only flush present addresses:
                 */
                if (pte && (pte_val(*pte) & _PAGE_PRESENT))
                        clflush_cache_range((void *) addr, PAGE_SIZE);
        }
}

static void cpa_flush_array(unsigned long *start, int numpages, int cache,
                            int in_flags, struct page **pages)
{
        unsigned int i, level;
        unsigned long do_wbinvd = cache && numpages >= 1024; /* 4M threshold */

        BUG_ON(irqs_disabled());

        on_each_cpu(__cpa_flush_all, (void *) do_wbinvd, 1);

        if (!cache || do_wbinvd)
                return;

        /*
         * We only need to flush on one CPU,
         * clflush is a MESI-coherent instruction that
         * will cause all other CPUs to flush the same
         * cachelines:
         */
        for (i = 0; i < numpages; i++) {
                unsigned long addr;
                pte_t *pte;

                if (in_flags & CPA_PAGES_ARRAY)
                        addr = (unsigned long)page_address(pages[i]);
                else
                        addr = start[i];

                pte = lookup_address(addr, &level);

                /*
                 * Only flush present addresses:
                 */
                if (pte && (pte_val(*pte) & _PAGE_PRESENT))
                        clflush_cache_range((void *)addr, PAGE_SIZE);
        }
}

/*
 * Certain areas of memory on x86 require very specific protection flags,
 * for example the BIOS area or kernel text. Callers don't always get this
 * right (again, ioremap() on BIOS memory is not uncommon) so this function
 * checks and fixes these known static required protection bits.
 */
static inline pgprot_t static_protections(pgprot_t prot, unsigned long address,
                                   unsigned long pfn)
{
        pgprot_t forbidden = __pgprot(0);

        /*
         * The BIOS area between 640k and 1Mb needs to be executable for
         * PCI BIOS based config access (CONFIG_PCI_GOBIOS) support.
         */
#ifdef CONFIG_PCI_BIOS
        if (pcibios_enabled && within(pfn, BIOS_BEGIN >> PAGE_SHIFT, BIOS_END >> PAGE_SHIFT))
                pgprot_val(forbidden) |= _PAGE_NX;
#endif

        /*
         * The kernel text needs to be executable for obvious reasons
         * Does not cover __inittext since that is gone later on. On
         * 64bit we do not enforce !NX on the low mapping
         */
        if (within(address, (unsigned long)_text, (unsigned long)_etext))
                pgprot_val(forbidden) |= _PAGE_NX;

        /*
         * The .rodata section needs to be read-only. Using the pfn
         * catches all aliases.
         */
        if (within(pfn, __pa((unsigned long)__start_rodata) >> PAGE_SHIFT,
                   __pa((unsigned long)__end_rodata) >> PAGE_SHIFT))
                pgprot_val(forbidden) |= _PAGE_RW;

#if defined(CONFIG_X86_64) && defined(CONFIG_DEBUG_RODATA)
        /*
         * Once the kernel maps the text as RO (kernel_set_to_readonly is set),
         * kernel text mappings for the large page aligned text, rodata sections
         * will be always read-only. For the kernel identity mappings covering
         * the holes caused by this alignment can be anything that user asks.
         *
         * This will preserve the large page mappings for kernel text/data
         * at no extra cost.
         */
        if (kernel_set_to_readonly &&
            within(address, (unsigned long)_text,
                   (unsigned long)__end_rodata_hpage_align)) {
                unsigned int level;

                /*
                 * Don't enforce the !RW mapping for the kernel text mapping,
                 * if the current mapping is already using small page mapping.
                 * No need to work hard to preserve large page mappings in this
                 * case.
                 *
                 * This also fixes the Linux Xen paravirt guest boot failure
                 * (because of unexpected read-only mappings for kernel identity
                 * mappings). In this paravirt guest case, the kernel text
                 * mapping and the kernel identity mapping share the same
                 * page-table pages. Thus we can't really use different
                 * protections for the kernel text and identity mappings. Also,
                 * these shared mappings are made of small page mappings.
                 * Thus this don't enforce !RW mapping for small page kernel
                 * text mapping logic will help Linux Xen parvirt guest boot
                 * aswell.
                 */
                if (lookup_address(address, &level) && (level != PG_LEVEL_4K))
                        pgprot_val(forbidden) |= _PAGE_RW;
        }
#endif

        prot = __pgprot(pgprot_val(prot) & ~pgprot_val(forbidden));

        return prot;
}

/*
 * Lookup the page table entry for a virtual address. Return a pointer
 * to the entry and the level of the mapping.
 *
 * Note: We return pud and pmd either when the entry is marked large
 * or when the present bit is not set. Otherwise we would return a
 * pointer to a nonexisting mapping.
 */
pte_t *lookup_address(unsigned long address, unsigned int *level)
{
        pgd_t *pgd = pgd_offset_k(address);
        pud_t *pud;
        pmd_t *pmd;

        *level = PG_LEVEL_NONE;

        if (pgd_none(*pgd))
                return NULL;

        pud = pud_offset(pgd, address);
        if (pud_none(*pud))
                return NULL;

        *level = PG_LEVEL_1G;
        if (pud_large(*pud) || !pud_present(*pud))
                return (pte_t *)pud;

        pmd = pmd_offset(pud, address);
        if (pmd_none(*pmd))
                return NULL;

        *level = PG_LEVEL_2M;
        if (pmd_large(*pmd) || !pmd_present(*pmd))
                return (pte_t *)pmd;

        *level = PG_LEVEL_4K;

        return pte_offset_kernel(pmd, address);
}
EXPORT_SYMBOL_GPL(lookup_address);

/*
 * Set the new pmd in all the pgds we know about:
 */
static void __set_pmd_pte(pte_t *kpte, unsigned long address, pte_t pte)
{
        /* change init_mm */
        set_pte_atomic(kpte, pte);
#ifdef CONFIG_X86_32
        if (!SHARED_KERNEL_PMD) {
                struct page *page;

                list_for_each_entry(page, &pgd_list, lru) {
                        pgd_t *pgd;
                        pud_t *pud;
                        pmd_t *pmd;

                        pgd = (pgd_t *)page_address(page) + pgd_index(address);
                        pud = pud_offset(pgd, address);
                        pmd = pmd_offset(pud, address);
                        set_pte_atomic((pte_t *)pmd, pte);
                }
        }
#endif
}

static int
try_preserve_large_page(pte_t *kpte, unsigned long address,
                        struct cpa_data *cpa)
{
        unsigned long nextpage_addr, numpages, pmask, psize, addr, pfn;
        pte_t new_pte, old_pte, *tmp;
        pgprot_t old_prot, new_prot, req_prot;
        int i, do_split = 1;
        unsigned int level;

        if (cpa->force_split)
                return 1;

        spin_lock(&pgd_lock);
        /*
         * Check for races, another CPU might have split this page
         * up already:
         */
        tmp = lookup_address(address, &level);
        if (tmp != kpte)
                goto out_unlock;

        switch (level) {
        case PG_LEVEL_2M:
                psize = PMD_PAGE_SIZE;
                pmask = PMD_PAGE_MASK;
                break;
#ifdef CONFIG_X86_64
        case PG_LEVEL_1G:
                psize = PUD_PAGE_SIZE;
                pmask = PUD_PAGE_MASK;
                break;
#endif
        default:
                do_split = -EINVAL;
                goto out_unlock;
        }

        /*
         * Calculate the number of pages, which fit into this large
         * page starting at address:
         */
        nextpage_addr = (address + psize) & pmask;
        numpages = (nextpage_addr - address) >> PAGE_SHIFT;
        if (numpages < cpa->numpages)
                cpa->numpages = numpages;

        /*
         * We are safe now. Check whether the new pgprot is the same:
         */
        old_pte = *kpte;
        old_prot = new_prot = req_prot = pte_pgprot(old_pte);

        pgprot_val(req_prot) &= ~pgprot_val(cpa->mask_clr);
        pgprot_val(req_prot) |= pgprot_val(cpa->mask_set);

        /*
         * old_pte points to the large page base address. So we need
         * to add the offset of the virtual address:
         */
        pfn = pte_pfn(old_pte) + ((address & (psize - 1)) >> PAGE_SHIFT);
        cpa->pfn = pfn;

        new_prot = static_protections(req_prot, address, pfn);

        /*
         * We need to check the full range, whether
         * static_protection() requires a different pgprot for one of
         * the pages in the range we try to preserve:
         */
        addr = address & pmask;
        pfn = pte_pfn(old_pte);
        for (i = 0; i < (psize >> PAGE_SHIFT); i++, addr += PAGE_SIZE, pfn++) {
                pgprot_t chk_prot = static_protections(req_prot, addr, pfn);

                if (pgprot_val(chk_prot) != pgprot_val(new_prot))
                        goto out_unlock;
        }

        /*
         * If there are no changes, return. maxpages has been updated
         * above:
         */
        if (pgprot_val(new_prot) == pgprot_val(old_prot)) {
                do_split = 0;
                goto out_unlock;
        }

        /*
         * We need to change the attributes. Check, whether we can
         * change the large page in one go. We request a split, when
         * the address is not aligned and the number of pages is
         * smaller than the number of pages in the large page. Note
         * that we limited the number of possible pages already to
         * the number of pages in the large page.
         */
        if (address == (address & pmask) && cpa->numpages == (psize >> PAGE_SHIFT)) {
                /*
                 * The address is aligned and the number of pages
                 * covers the full page.
                 */
                new_pte = pfn_pte(pte_pfn(old_pte), canon_pgprot(new_prot));
                __set_pmd_pte(kpte, address, new_pte);
                cpa->flags |= CPA_FLUSHTLB;
                do_split = 0;
        }

out_unlock:
        spin_unlock(&pgd_lock);

        return do_split;
}

static int split_large_page(pte_t *kpte, unsigned long address)
{
        unsigned long pfn, pfninc = 1;
        unsigned int i, level;
        pte_t *pbase, *tmp;
        pgprot_t ref_prot;
        struct page *base;

        if (!debug_pagealloc)
                spin_unlock(&cpa_lock);
        base = alloc_pages(GFP_KERNEL | __GFP_NOTRACK, 0);
        if (!debug_pagealloc)
                spin_lock(&cpa_lock);
        if (!base)
                return -ENOMEM;

        spin_lock(&pgd_lock);
        /*
         * Check for races, another CPU might have split this page
         * up for us already:
         */
        tmp = lookup_address(address, &level);
        if (tmp != kpte)
                goto out_unlock;

        pbase = (pte_t *)page_address(base);
        paravirt_alloc_pte(&init_mm, page_to_pfn(base));
        ref_prot = pte_pgprot(pte_clrhuge(*kpte));
        /*
         * If we ever want to utilize the PAT bit, we need to
         * update this function to make sure it's converted from
         * bit 12 to bit 7 when we cross from the 2MB level to
         * the 4K level:
         */
        WARN_ON_ONCE(pgprot_val(ref_prot) & _PAGE_PAT_LARGE);

#ifdef CONFIG_X86_64
        if (level == PG_LEVEL_1G) {
                pfninc = PMD_PAGE_SIZE >> PAGE_SHIFT;
                pgprot_val(ref_prot) |= _PAGE_PSE;
        }
#endif

        /*
         * Get the target pfn from the original entry:
         */
        pfn = pte_pfn(*kpte);
        for (i = 0; i < PTRS_PER_PTE; i++, pfn += pfninc)
                set_pte(&pbase[i], pfn_pte(pfn, ref_prot));

        if (address >= (unsigned long)__va(0) &&
                address < (unsigned long)__va(max_low_pfn_mapped << PAGE_SHIFT))
                split_page_count(level);

#ifdef CONFIG_X86_64
        if (address >= (unsigned long)__va(1UL<<32) &&
                address < (unsigned long)__va(max_pfn_mapped << PAGE_SHIFT))
                split_page_count(level);
#endif

        /*
         * Install the new, split up pagetable.
         *
         * We use the standard kernel pagetable protections for the new
         * pagetable protections, the actual ptes set above control the
         * primary protection behavior:
         */
        __set_pmd_pte(kpte, address, mk_pte(base, __pgprot(_KERNPG_TABLE)));

        /*
         * Intel Atom errata AAH41 workaround.
         *
         * The real fix should be in hw or in a microcode update, but
         * we also probabilistically try to reduce the window of having
         * a large TLB mixed with 4K TLBs while instruction fetches are
         * going on.
         */
        __flush_tlb_all();

        base = NULL;

out_unlock:
        /*
         * If we dropped out via the lookup_address check under
         * pgd_lock then stick the page back into the pool:
         */
        if (base)
                __free_page(base);
        spin_unlock(&pgd_lock);

        return 0;
}

static int __cpa_process_fault(struct cpa_data *cpa, unsigned long vaddr,
                               int primary)
{
        /*
         * Ignore all non primary paths.
         */
        if (!primary)
                return 0;

        /*
         * Ignore the NULL PTE for kernel identity mapping, as it is expected
         * to have holes.
         * Also set numpages to '1' indicating that we processed cpa req for
         * one virtual address page and its pfn. TBD: numpages can be set based
         * on the initial value and the level returned by lookup_address().
         */
        if (within(vaddr, PAGE_OFFSET,
                   PAGE_OFFSET + (max_pfn_mapped << PAGE_SHIFT))) {
                cpa->numpages = 1;
                cpa->pfn = __pa(vaddr) >> PAGE_SHIFT;
                return 0;
        } else {
                WARN(1, KERN_WARNING "CPA: called for zero pte. "
                        "vaddr = %lx cpa->vaddr = %lx\n", vaddr,
                        *cpa->vaddr);

                return -EFAULT;
        }
}

static int __change_page_attr(struct cpa_data *cpa, int primary)
{
        unsigned long address;
        int do_split, err;
        unsigned int level;
        pte_t *kpte, old_pte;

        if (cpa->flags & CPA_PAGES_ARRAY) {
                struct page *page = cpa->pages[cpa->curpage];
                if (unlikely(PageHighMem(page)))
                        return 0;
                address = (unsigned long)page_address(page);
        } else if (cpa->flags & CPA_ARRAY)
                address = cpa->vaddr[cpa->curpage];
        else
                address = *cpa->vaddr;
repeat:
        kpte = lookup_address(address, &level);
        if (!kpte)
                return __cpa_process_fault(cpa, address, primary);

        old_pte = *kpte;
        if (!pte_val(old_pte))
                return __cpa_process_fault(cpa, address, primary);

        if (level == PG_LEVEL_4K) {
                pte_t new_pte;
                pgprot_t new_prot = pte_pgprot(old_pte);
                unsigned long pfn = pte_pfn(old_pte);

                pgprot_val(new_prot) &= ~pgprot_val(cpa->mask_clr);
                pgprot_val(new_prot) |= pgprot_val(cpa->mask_set);

                new_prot = static_protections(new_prot, address, pfn);

                /*
                 * We need to keep the pfn from the existing PTE,
                 * after all we're only going to change it's attributes
                 * not the memory it points to
                 */
                new_pte = pfn_pte(pfn, canon_pgprot(new_prot));
                cpa->pfn = pfn;
                /*
                 * Do we really change anything ?
                 */
                if (pte_val(old_pte) != pte_val(new_pte)) {
                        set_pte_atomic(kpte, new_pte);
                        cpa->flags |= CPA_FLUSHTLB;
                }
                cpa->numpages = 1;
                return 0;
        }

        /*
         * Check, whether we can keep the large page intact
         * and just change the pte:
         */
        do_split = try_preserve_large_page(kpte, address, cpa);
        /*
         * When the range fits into the existing large page,
         * return. cp->numpages and cpa->tlbflush have been updated in
         * try_large_page:
         */
        if (do_split <= 0)
                return do_split;

        /*
         * We have to split the large page:
         */
        err = split_large_page(kpte, address);
        if (!err) {
                /*
                 * Do a global flush tlb after splitting the large page
                 * and before we do the actual change page attribute in the PTE.
                 *
                 * With out this, we violate the TLB application note, that says
                 * "The TLBs may contain both ordinary and large-page
                 *  translations for a 4-KByte range of linear addresses. This
                 *  may occur if software modifies the paging structures so that
                 *  the page size used for the address range changes. If the two
                 *  translations differ with respect to page frame or attributes
                 *  (e.g., permissions), processor behavior is undefined and may
                 *  be implementation-specific."
                 *
                 * We do this global tlb flush inside the cpa_lock, so that we
                 * don't allow any other cpu, with stale tlb entries change the
                 * page attribute in parallel, that also falls into the
                 * just split large page entry.
                 */
                flush_tlb_all();
                goto repeat;
        }

        return err;
}

static int __change_page_attr_set_clr(struct cpa_data *cpa, int checkalias);

static int cpa_process_alias(struct cpa_data *cpa)
{
        struct cpa_data alias_cpa;
        unsigned long laddr = (unsigned long)__va(cpa->pfn << PAGE_SHIFT);
        unsigned long vaddr;
        int ret;

        if (cpa->pfn >= max_pfn_mapped)
                return 0;

#ifdef CONFIG_X86_64
        if (cpa->pfn >= max_low_pfn_mapped && cpa->pfn < (1UL<<(32-PAGE_SHIFT)))
                return 0;
#endif
        /*
         * No need to redo, when the primary call touched the direct
         * mapping already:
         */
        if (cpa->flags & CPA_PAGES_ARRAY) {
                struct page *page = cpa->pages[cpa->curpage];
                if (unlikely(PageHighMem(page)))
                        return 0;
                vaddr = (unsigned long)page_address(page);
        } else if (cpa->flags & CPA_ARRAY)
                vaddr = cpa->vaddr[cpa->curpage];
        else
                vaddr = *cpa->vaddr;

        if (!(within(vaddr, PAGE_OFFSET,
                    PAGE_OFFSET + (max_pfn_mapped << PAGE_SHIFT)))) {

                alias_cpa = *cpa;
                alias_cpa.vaddr = &laddr;
                alias_cpa.flags &= ~(CPA_PAGES_ARRAY | CPA_ARRAY);

                ret = __change_page_attr_set_clr(&alias_cpa, 0);
                if (ret)
                        return ret;
        }

#ifdef CONFIG_X86_64
        /*
         * If the primary call didn't touch the high mapping already
         * and the physical address is inside the kernel map, we need
         * to touch the high mapped kernel as well:
         */
        if (!within(vaddr, (unsigned long)_text, _brk_end) &&
            within(cpa->pfn, highmap_start_pfn(), highmap_end_pfn())) {
                unsigned long temp_cpa_vaddr = (cpa->pfn << PAGE_SHIFT) +
                                               __START_KERNEL_map - phys_base;
                alias_cpa = *cpa;
                alias_cpa.vaddr = &temp_cpa_vaddr;
                alias_cpa.flags &= ~(CPA_PAGES_ARRAY | CPA_ARRAY);

                /*
                 * The high mapping range is imprecise, so ignore the
                 * return value.
                 */
                __change_page_attr_set_clr(&alias_cpa, 0);
        }
#endif

        return 0;
}

static int __change_page_attr_set_clr(struct cpa_data *cpa, int checkalias)
{
        int ret, numpages = cpa->numpages;

        while (numpages) {
                /*
                 * Store the remaining nr of pages for the large page
                 * preservation check.
                 */
                cpa->numpages = numpages;
                /* for array changes, we can't use large page */
                if (cpa->flags & (CPA_ARRAY | CPA_PAGES_ARRAY))
                        cpa->numpages = 1;

                if (!debug_pagealloc)
                        spin_lock(&cpa_lock);
                ret = __change_page_attr(cpa, checkalias);
                if (!debug_pagealloc)
                        spin_unlock(&cpa_lock);
                if (ret)
                        return ret;

                if (checkalias) {
                        ret = cpa_process_alias(cpa);
                        if (ret)
                                return ret;
                }

                /*
                 * Adjust the number of pages with the result of the
                 * CPA operation. Either a large page has been
                 * preserved or a single page update happened.
                 */
                BUG_ON(cpa->numpages > numpages);
                numpages -= cpa->numpages;
                if (cpa->flags & (CPA_PAGES_ARRAY | CPA_ARRAY))
                        cpa->curpage++;
                else
                        *cpa->vaddr += cpa->numpages * PAGE_SIZE;

        }
        return 0;
}

static inline int cache_attr(pgprot_t attr)
{
        return pgprot_val(attr) &
                (_PAGE_PAT | _PAGE_PAT_LARGE | _PAGE_PWT | _PAGE_PCD);
}

static int change_page_attr_set_clr(unsigned long *addr, int numpages,
                                    pgprot_t mask_set, pgprot_t mask_clr,
                                    int force_split, int in_flag,
                                    struct page **pages)
{
        struct cpa_data cpa;
        int ret, cache, checkalias;
        unsigned long baddr = 0;

        /*
         * Check, if we are requested to change a not supported
         * feature:
         */
        mask_set = canon_pgprot(mask_set);
        mask_clr = canon_pgprot(mask_clr);
        if (!pgprot_val(mask_set) && !pgprot_val(mask_clr) && !force_split)
                return 0;

        /* Ensure we are PAGE_SIZE aligned */
        if (in_flag & CPA_ARRAY) {
                int i;
                for (i = 0; i < numpages; i++) {
                        if (addr[i] & ~PAGE_MASK) {
                                addr[i] &= PAGE_MASK;
                                WARN_ON_ONCE(1);
                        }
                }
        } else if (!(in_flag & CPA_PAGES_ARRAY)) {
                /*
                 * in_flag of CPA_PAGES_ARRAY implies it is aligned.
                 * No need to cehck in that case
                 */
                if (*addr & ~PAGE_MASK) {
                        *addr &= PAGE_MASK;
                        /*
                         * People should not be passing in unaligned addresses:
                         */
                        WARN_ON_ONCE(1);
                }
                /*
                 * Save address for cache flush. *addr is modified in the call
                 * to __change_page_attr_set_clr() below.
                 */
                baddr = *addr;
        }

        /* Must avoid aliasing mappings in the highmem code */
        kmap_flush_unused();

        vm_unmap_aliases();

        cpa.vaddr = addr;
        cpa.pages = pages;
        cpa.numpages = numpages;
        cpa.mask_set = mask_set;
        cpa.mask_clr = mask_clr;
        cpa.flags = 0;
        cpa.curpage = 0;
        cpa.force_split = force_split;

        if (in_flag & (CPA_ARRAY | CPA_PAGES_ARRAY))
                cpa.flags |= in_flag;

        /* No alias checking for _NX bit modifications */
        checkalias = (pgprot_val(mask_set) | pgprot_val(mask_clr)) != _PAGE_NX;

        ret = __change_page_attr_set_clr(&cpa, checkalias);

        /*
         * Check whether we really changed something:
         */
        if (!(cpa.flags & CPA_FLUSHTLB))
                goto out;

        /*
         * No need to flush, when we did not set any of the caching
         * attributes:
         */
        cache = cache_attr(mask_set);

        /*
         * On success we use clflush, when the CPU supports it to
         * avoid the wbindv. If the CPU does not support it and in the
         * error case we fall back to cpa_flush_all (which uses
         * wbindv):
         */
        if (!ret && cpu_has_clflush) {
                if (cpa.flags & (CPA_PAGES_ARRAY | CPA_ARRAY)) {
                        cpa_flush_array(addr, numpages, cache,
                                        cpa.flags, pages);
                } else
                        cpa_flush_range(baddr, numpages, cache);
        } else
                cpa_flush_all(cache);

out:
        return ret;
}

static inline int change_page_attr_set(unsigned long *addr, int numpages,
                                       pgprot_t mask, int array)
{
        return change_page_attr_set_clr(addr, numpages, mask, __pgprot(0), 0,
                (array ? CPA_ARRAY : 0), NULL);
}

static inline int change_page_attr_clear(unsigned long *addr, int numpages,
                                         pgprot_t mask, int array)
{
        return change_page_attr_set_clr(addr, numpages, __pgprot(0), mask, 0,
                (array ? CPA_ARRAY : 0), NULL);
}

static inline int cpa_set_pages_array(struct page **pages, int numpages,
                                       pgprot_t mask)
{
        return change_page_attr_set_clr(NULL, numpages, mask, __pgprot(0), 0,
                CPA_PAGES_ARRAY, pages);
}

static inline int cpa_clear_pages_array(struct page **pages, int numpages,
                                         pgprot_t mask)
{
        return change_page_attr_set_clr(NULL, numpages, __pgprot(0), mask, 0,
                CPA_PAGES_ARRAY, pages);
}

int _set_memory_uc(unsigned long addr, int numpages)
{
        /*
         * for now UC MINUS. see comments in ioremap_nocache()
         */
        return change_page_attr_set(&addr, numpages,
                                    __pgprot(_PAGE_CACHE_UC_MINUS), 0);
}

int set_memory_uc(unsigned long addr, int numpages)
{
        int ret;

        /*
         * for now UC MINUS. see comments in ioremap_nocache()
         */
        ret = reserve_memtype(__pa(addr), __pa(addr) + numpages * PAGE_SIZE,
                            _PAGE_CACHE_UC_MINUS, NULL);
        if (ret)
                goto out_err;

        ret = _set_memory_uc(addr, numpages);
        if (ret)
                goto out_free;

        return 0;

out_free:
        free_memtype(__pa(addr), __pa(addr) + numpages * PAGE_SIZE);
out_err:
        return ret;
}
EXPORT_SYMBOL(set_memory_uc);

int _set_memory_array(unsigned long *addr, int addrinarray,
                unsigned long new_type)
{
        int i, j;
        int ret;

        /*
         * for now UC MINUS. see comments in ioremap_nocache()
         */
        for (i = 0; i < addrinarray; i++) {
                ret = reserve_memtype(__pa(addr[i]), __pa(addr[i]) + PAGE_SIZE,
                                        new_type, NULL);
                if (ret)
                        goto out_free;
        }

        ret = change_page_attr_set(addr, addrinarray,
                                    __pgprot(_PAGE_CACHE_UC_MINUS), 1);

        if (!ret && new_type == _PAGE_CACHE_WC)
                ret = change_page_attr_set_clr(addr, addrinarray,
                                               __pgprot(_PAGE_CACHE_WC),
                                               __pgprot(_PAGE_CACHE_MASK),
                                               0, CPA_ARRAY, NULL);
        if (ret)
                goto out_free;

        return 0;

out_free:
        for (j = 0; j < i; j++)
                free_memtype(__pa(addr[j]), __pa(addr[j]) + PAGE_SIZE);

        return ret;
}

int set_memory_array_uc(unsigned long *addr, int addrinarray)
{
        return _set_memory_array(addr, addrinarray, _PAGE_CACHE_UC_MINUS);
}
EXPORT_SYMBOL(set_memory_array_uc);

int set_memory_array_wc(unsigned long *addr, int addrinarray)
{
        return _set_memory_array(addr, addrinarray, _PAGE_CACHE_WC);
}
EXPORT_SYMBOL(set_memory_array_wc);

int _set_memory_wc(unsigned long addr, int numpages)
{
        int ret;
        unsigned long addr_copy = addr;

        ret = change_page_attr_set(&addr, numpages,
                                    __pgprot(_PAGE_CACHE_UC_MINUS), 0);
        if (!ret) {
                ret = change_page_attr_set_clr(&addr_copy, numpages,
                                               __pgprot(_PAGE_CACHE_WC),
                                               __pgprot(_PAGE_CACHE_MASK),
                                               0, 0, NULL);
        }
        return ret;
}

int set_memory_wc(unsigned long addr, int numpages)
{
        int ret;

        if (!pat_enabled)
                return set_memory_uc(addr, numpages);

        ret = reserve_memtype(__pa(addr), __pa(addr) + numpages * PAGE_SIZE,
                _PAGE_CACHE_WC, NULL);
        if (ret)
                goto out_err;

        ret = _set_memory_wc(addr, numpages);
        if (ret)
                goto out_free;

        return 0;

out_free:
        free_memtype(__pa(addr), __pa(addr) + numpages * PAGE_SIZE);
out_err:
        return ret;
}
EXPORT_SYMBOL(set_memory_wc);

int _set_memory_wb(unsigned long addr, int numpages)
{
        return change_page_attr_clear(&addr, numpages,
                                      __pgprot(_PAGE_CACHE_MASK), 0);
}

int set_memory_wb(unsigned long addr, int numpages)
{
        int ret;

        ret = _set_memory_wb(addr, numpages);
        if (ret)
                return ret;

        free_memtype(__pa(addr), __pa(addr) + numpages * PAGE_SIZE);
        return 0;
}
EXPORT_SYMBOL(set_memory_wb);

int set_memory_array_wb(unsigned long *addr, int addrinarray)
{
        int i;
        int ret;

        ret = change_page_attr_clear(addr, addrinarray,
                                      __pgprot(_PAGE_CACHE_MASK), 1);
        if (ret)
                return ret;

        for (i = 0; i < addrinarray; i++)
                free_memtype(__pa(addr[i]), __pa(addr[i]) + PAGE_SIZE);

        return 0;
}
EXPORT_SYMBOL(set_memory_array_wb);

int set_memory_x(unsigned long addr, int numpages)
{
        if (!(__supported_pte_mask & _PAGE_NX))
                return 0;

        return change_page_attr_clear(&addr, numpages, __pgprot(_PAGE_NX), 0);
}
EXPORT_SYMBOL(set_memory_x);

int set_memory_nx(unsigned long addr, int numpages)
{
        if (!(__supported_pte_mask & _PAGE_NX))
                return 0;

        return change_page_attr_set(&addr, numpages, __pgprot(_PAGE_NX), 0);
}
EXPORT_SYMBOL(set_memory_nx);

int set_memory_ro(unsigned long addr, int numpages)
{
        return change_page_attr_clear(&addr, numpages, __pgprot(_PAGE_RW), 0);
}
EXPORT_SYMBOL_GPL(set_memory_ro);

int set_memory_rw(unsigned long addr, int numpages)
{
        return change_page_attr_set(&addr, numpages, __pgprot(_PAGE_RW), 0);
}
EXPORT_SYMBOL_GPL(set_memory_rw);

int set_memory_np(unsigned long addr, int numpages)
{
        return change_page_attr_clear(&addr, numpages, __pgprot(_PAGE_PRESENT), 0);
}

int set_memory_4k(unsigned long addr, int numpages)
{
        return change_page_attr_set_clr(&addr, numpages, __pgprot(0),
                                        __pgprot(0), 1, 0, NULL);
}

int set_pages_uc(struct page *page, int numpages)
{
        unsigned long addr = (unsigned long)page_address(page);

        return set_memory_uc(addr, numpages);
}
EXPORT_SYMBOL(set_pages_uc);

static int _set_pages_array(struct page **pages, int addrinarray,
                unsigned long new_type)
{
        unsigned long start;
        unsigned long end;
        int i;
        int free_idx;
        int ret;

        for (i = 0; i < addrinarray; i++) {
                if (PageHighMem(pages[i]))
                        continue;
                start = page_to_pfn(pages[i]) << PAGE_SHIFT;
                end = start + PAGE_SIZE;
                if (reserve_memtype(start, end, new_type, NULL))
                        goto err_out;
        }

        ret = cpa_set_pages_array(pages, addrinarray,
                        __pgprot(_PAGE_CACHE_UC_MINUS));
        if (!ret && new_type == _PAGE_CACHE_WC)
                ret = change_page_attr_set_clr(NULL, addrinarray,
                                               __pgprot(_PAGE_CACHE_WC),
                                               __pgprot(_PAGE_CACHE_MASK),
                                               0, CPA_PAGES_ARRAY, pages);
        if (ret)
                goto err_out;
        return 0; /* Success */
err_out:
        free_idx = i;
        for (i = 0; i < free_idx; i++) {
                if (PageHighMem(pages[i]))
                        continue;
                start = page_to_pfn(pages[i]) << PAGE_SHIFT;
                end = start + PAGE_SIZE;
                free_memtype(start, end);
        }
        return -EINVAL;
}

int set_pages_array_uc(struct page **pages, int addrinarray)
{
        return _set_pages_array(pages, addrinarray, _PAGE_CACHE_UC_MINUS);
}
EXPORT_SYMBOL(set_pages_array_uc);

int set_pages_array_wc(struct page **pages, int addrinarray)
{
        return _set_pages_array(pages, addrinarray, _PAGE_CACHE_WC);
}
EXPORT_SYMBOL(set_pages_array_wc);

int set_pages_wb(struct page *page, int numpages)
{
        unsigned long addr = (unsigned long)page_address(page);

        return set_memory_wb(addr, numpages);
}
EXPORT_SYMBOL(set_pages_wb);

int set_pages_array_wb(struct page **pages, int addrinarray)
{
        int retval;
        unsigned long start;
        unsigned long end;
        int i;

        retval = cpa_clear_pages_array(pages, addrinarray,
                        __pgprot(_PAGE_CACHE_MASK));
        if (retval)
                return retval;

        for (i = 0; i < addrinarray; i++) {
                if (PageHighMem(pages[i]))
                        continue;
                start = page_to_pfn(pages[i]) << PAGE_SHIFT;
                end = start + PAGE_SIZE;
                free_memtype(start, end);
        }

        return 0;
}
EXPORT_SYMBOL(set_pages_array_wb);

int set_pages_x(struct page *page, int numpages)
{
        unsigned long addr = (unsigned long)page_address(page);

        return set_memory_x(addr, numpages);
}
EXPORT_SYMBOL(set_pages_x);

int set_pages_nx(struct page *page, int numpages)
{
        unsigned long addr = (unsigned long)page_address(page);

        return set_memory_nx(addr, numpages);
}
EXPORT_SYMBOL(set_pages_nx);

int set_pages_ro(struct page *page, int numpages)
{
        unsigned long addr = (unsigned long)page_address(page);

        return set_memory_ro(addr, numpages);
}

int set_pages_rw(struct page *page, int numpages)
{
        unsigned long addr = (unsigned long)page_address(page);

        return set_memory_rw(addr, numpages);
}

#ifdef CONFIG_DEBUG_PAGEALLOC

static int __set_pages_p(struct page *page, int numpages)
{
        unsigned long tempaddr = (unsigned long) page_address(page);
        struct cpa_data cpa = { .vaddr = &tempaddr,
                                .numpages = numpages,
                                .mask_set = __pgprot(_PAGE_PRESENT | _PAGE_RW),
                                .mask_clr = __pgprot(0),
                                .flags = 0};

        /*
         * No alias checking needed for setting present flag. otherwise,
         * we may need to break large pages for 64-bit kernel text
         * mappings (this adds to complexity if we want to do this from
         * atomic context especially). Let's keep it simple!
         */
        return __change_page_attr_set_clr(&cpa, 0);
}

static int __set_pages_np(struct page *page, int numpages)
{
        unsigned long tempaddr = (unsigned long) page_address(page);
        struct cpa_data cpa = { .vaddr = &tempaddr,
                                .numpages = numpages,
                                .mask_set = __pgprot(0),
                                .mask_clr = __pgprot(_PAGE_PRESENT | _PAGE_RW),
                                .flags = 0};

        /*
         * No alias checking needed for setting not present flag. otherwise,
         * we may need to break large pages for 64-bit kernel text
         * mappings (this adds to complexity if we want to do this from
         * atomic context especially). Let's keep it simple!
         */
        return __change_page_attr_set_clr(&cpa, 0);
}

void kernel_map_pages(struct page *page, int numpages, int enable)
{
        if (PageHighMem(page))
                return;
        if (!enable) {
                debug_check_no_locks_freed(page_address(page),
                                           numpages * PAGE_SIZE);
        }

        /*
         * If page allocator is not up yet then do not call c_p_a():
         */
        if (!debug_pagealloc_enabled)
                return;

        /*
         * The return value is ignored as the calls cannot fail.
         * Large pages for identity mappings are not used at boot time
         * and hence no memory allocations during large page split.
         */
        if (enable)
                __set_pages_p(page, numpages);
        else
                __set_pages_np(page, numpages);

        /*
         * We should perform an IPI and flush all tlbs,
         * but that can deadlock->flush only current cpu:
         */
        __flush_tlb_all();
}

#ifdef CONFIG_HIBERNATION

bool kernel_page_present(struct page *page)
{
        unsigned int level;
        pte_t *pte;

        if (PageHighMem(page))
                return false;

        pte = lookup_address((unsigned long)page_address(page), &level);
        return (pte_val(*pte) & _PAGE_PRESENT);
}

#endif /* CONFIG_HIBERNATION */

#endif /* CONFIG_DEBUG_PAGEALLOC */

/*
 * The testcases use internal knowledge of the implementation that shouldn't
 * be exposed to the rest of the kernel. Include these directly here.
 */
#ifdef CONFIG_CPA_DEBUG
#include "pageattr-test.c"
#endif