source: trunk/packages/xen-3.1/xen-3.1/linux-2.6-xen-sparse/arch/x86_64/mm/pageattr-xen.c @ 34

/* 
 * Copyright 2002 Andi Kleen, SuSE Labs. 
 * Thanks to Ben LaHaise for precious feedback.
 */ 

#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/highmem.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <asm/uaccess.h>
#include <asm/processor.h>
#include <asm/tlbflush.h>
#include <asm/io.h>

#ifdef CONFIG_XEN
#include <asm/pgalloc.h>
#include <asm/mmu_context.h>

LIST_HEAD(mm_unpinned);
DEFINE_SPINLOCK(mm_unpinned_lock);

static inline void mm_walk_set_prot(void *pt, pgprot_t flags)
{
        struct page *page = virt_to_page(pt);
        unsigned long pfn = page_to_pfn(page);
        int rc;

        rc = HYPERVISOR_update_va_mapping(
                (unsigned long)__va(pfn << PAGE_SHIFT),
                pfn_pte(pfn, flags), 0);
        if (rc)
                BUG();
}

static void mm_walk(struct mm_struct *mm, pgprot_t flags)
{
        pgd_t       *pgd;
        pud_t       *pud;
        pmd_t       *pmd;
        pte_t       *pte;
        int          g,u,m;

        pgd = mm->pgd;
        /*
         * Cannot iterate up to USER_PTRS_PER_PGD as these pagetables may not
         * be the 'current' task's pagetables (e.g., current may be 32-bit,
         * but the pagetables may be for a 64-bit task).
         * Subtracting 1 from TASK_SIZE64 means the loop limit is correct
         * regardless of whether TASK_SIZE64 is a multiple of PGDIR_SIZE.
         */
        for (g = 0; g <= ((TASK_SIZE64-1) / PGDIR_SIZE); g++, pgd++) {
                if (pgd_none(*pgd))
                        continue;
                pud = pud_offset(pgd, 0);
                if (PTRS_PER_PUD > 1) /* not folded */ 
                        mm_walk_set_prot(pud,flags);
                for (u = 0; u < PTRS_PER_PUD; u++, pud++) {
                        if (pud_none(*pud))
                                continue;
                        pmd = pmd_offset(pud, 0);
                        if (PTRS_PER_PMD > 1) /* not folded */ 
                                mm_walk_set_prot(pmd,flags);
                        for (m = 0; m < PTRS_PER_PMD; m++, pmd++) {
                                if (pmd_none(*pmd))
                                        continue;
                                pte = pte_offset_kernel(pmd,0);
                                mm_walk_set_prot(pte,flags);
                        }
                }
        }
}

void mm_pin(struct mm_struct *mm)
{
        if (xen_feature(XENFEAT_writable_page_tables))
                return;

        spin_lock(&mm->page_table_lock);

        mm_walk(mm, PAGE_KERNEL_RO);
        if (HYPERVISOR_update_va_mapping(
                (unsigned long)mm->pgd,
                pfn_pte(virt_to_phys(mm->pgd)>>PAGE_SHIFT, PAGE_KERNEL_RO),
                UVMF_TLB_FLUSH))
                BUG();
        if (HYPERVISOR_update_va_mapping(
                (unsigned long)__user_pgd(mm->pgd),
                pfn_pte(virt_to_phys(__user_pgd(mm->pgd))>>PAGE_SHIFT,
                        PAGE_KERNEL_RO),
                UVMF_TLB_FLUSH))
                BUG();
        xen_pgd_pin(__pa(mm->pgd)); /* kernel */
        xen_pgd_pin(__pa(__user_pgd(mm->pgd))); /* user */
        mm->context.pinned = 1;
        spin_lock(&mm_unpinned_lock);
        list_del(&mm->context.unpinned);
        spin_unlock(&mm_unpinned_lock);

        spin_unlock(&mm->page_table_lock);
}

void mm_unpin(struct mm_struct *mm)
{
        if (xen_feature(XENFEAT_writable_page_tables))
                return;

        spin_lock(&mm->page_table_lock);

        xen_pgd_unpin(__pa(mm->pgd));
        xen_pgd_unpin(__pa(__user_pgd(mm->pgd)));
        if (HYPERVISOR_update_va_mapping(
                (unsigned long)mm->pgd,
                pfn_pte(virt_to_phys(mm->pgd)>>PAGE_SHIFT, PAGE_KERNEL), 0))
                BUG();
        if (HYPERVISOR_update_va_mapping(
                (unsigned long)__user_pgd(mm->pgd),
                pfn_pte(virt_to_phys(__user_pgd(mm->pgd))>>PAGE_SHIFT,
                        PAGE_KERNEL), 0))
                BUG();
        mm_walk(mm, PAGE_KERNEL);
        xen_tlb_flush();
        mm->context.pinned = 0;
        spin_lock(&mm_unpinned_lock);
        list_add(&mm->context.unpinned, &mm_unpinned);
        spin_unlock(&mm_unpinned_lock);

        spin_unlock(&mm->page_table_lock);
}

void mm_pin_all(void)
{
        if (xen_feature(XENFEAT_writable_page_tables))
                return;

        /*
         * Allow uninterrupted access to the mm_unpinned list. We don't
         * actually take the mm_unpinned_lock as it is taken inside mm_pin().
         * All other CPUs must be at a safe point (e.g., in stop_machine
         * or offlined entirely).
         */
        preempt_disable();
        while (!list_empty(&mm_unpinned))       
                mm_pin(list_entry(mm_unpinned.next, struct mm_struct,
                                  context.unpinned));
        preempt_enable();
}

void _arch_dup_mmap(struct mm_struct *mm)
{
        if (!mm->context.pinned)
                mm_pin(mm);
}

void _arch_exit_mmap(struct mm_struct *mm)
{
        struct task_struct *tsk = current;

        task_lock(tsk);

        /*
         * We aggressively remove defunct pgd from cr3. We execute unmap_vmas()
         * *much* faster this way, as no tlb flushes means bigger wrpt batches.
         */
        if (tsk->active_mm == mm) {
                tsk->active_mm = &init_mm;
                atomic_inc(&init_mm.mm_count);

                switch_mm(mm, &init_mm, tsk);

                atomic_dec(&mm->mm_count);
                BUG_ON(atomic_read(&mm->mm_count) == 0);
        }

        task_unlock(tsk);

        if ( mm->context.pinned && (atomic_read(&mm->mm_count) == 1) &&
             !mm->context.has_foreign_mappings )
                mm_unpin(mm);
}

struct page *pte_alloc_one(struct mm_struct *mm, unsigned long address)
{
        struct page *pte;

        pte = alloc_pages(GFP_KERNEL|__GFP_REPEAT|__GFP_ZERO, 0);
        if (pte) {
                SetPageForeign(pte, pte_free);
                init_page_count(pte);
        }
        return pte;
}

void pte_free(struct page *pte)
{
        unsigned long va = (unsigned long)__va(page_to_pfn(pte)<<PAGE_SHIFT);

        if (!pte_write(*virt_to_ptep(va)))
                if (HYPERVISOR_update_va_mapping(
                        va, pfn_pte(page_to_pfn(pte), PAGE_KERNEL), 0))
                        BUG();

        ClearPageForeign(pte);
        init_page_count(pte);

        __free_page(pte);
}
#endif  /* CONFIG_XEN */

static inline pte_t *lookup_address(unsigned long address) 
{ 
        pgd_t *pgd = pgd_offset_k(address);
        pud_t *pud;
        pmd_t *pmd;
        pte_t *pte;
        if (pgd_none(*pgd))
                return NULL;
        pud = pud_offset(pgd, address);
        if (!pud_present(*pud))
                return NULL; 
        pmd = pmd_offset(pud, address);
        if (!pmd_present(*pmd))
                return NULL; 
        if (pmd_large(*pmd))
                return (pte_t *)pmd;
        pte = pte_offset_kernel(pmd, address);
        if (pte && !pte_present(*pte))
                pte = NULL; 
        return pte;
} 

static struct page *split_large_page(unsigned long address, pgprot_t prot,
                                     pgprot_t ref_prot)
{ 
        int i; 
        unsigned long addr;
        struct page *base = alloc_pages(GFP_KERNEL, 0);
        pte_t *pbase;
        if (!base) 
                return NULL;
        /*
         * page_private is used to track the number of entries in
         * the page table page have non standard attributes.
         */
        SetPagePrivate(base);
        page_private(base) = 0;

        address = __pa(address);
        addr = address & LARGE_PAGE_MASK; 
        pbase = (pte_t *)page_address(base);
        for (i = 0; i < PTRS_PER_PTE; i++, addr += PAGE_SIZE) {
                pbase[i] = pfn_pte(addr >> PAGE_SHIFT, 
                                   addr == address ? prot : ref_prot);
        }
        return base;
} 


static void flush_kernel_map(void *address) 
{
        if (0 && address && cpu_has_clflush) {
                /* is this worth it? */ 
                int i;
                for (i = 0; i < PAGE_SIZE; i += boot_cpu_data.x86_clflush_size) 
                        asm volatile("clflush (%0)" :: "r" (address + i)); 
        } else
                asm volatile("wbinvd":::"memory"); 
        if (address)
                __flush_tlb_one(address);
        else
                __flush_tlb_all();
}


static inline void flush_map(unsigned long address)
{       
        on_each_cpu(flush_kernel_map, (void *)address, 1, 1);
}

static struct page *deferred_pages; /* protected by init_mm.mmap_sem */

static inline void save_page(struct page *fpage)
{
        fpage->lru.next = (struct list_head *)deferred_pages;
        deferred_pages = fpage;
}

/* 
 * No more special protections in this 2/4MB area - revert to a
 * large page again. 
 */
static void revert_page(unsigned long address, pgprot_t ref_prot)
{
        pgd_t *pgd;
        pud_t *pud;
        pmd_t *pmd;
        pte_t large_pte;

        pgd = pgd_offset_k(address);
        BUG_ON(pgd_none(*pgd));
        pud = pud_offset(pgd,address);
        BUG_ON(pud_none(*pud));
        pmd = pmd_offset(pud, address);
        BUG_ON(pmd_val(*pmd) & _PAGE_PSE);
        pgprot_val(ref_prot) |= _PAGE_PSE;
        large_pte = mk_pte_phys(__pa(address) & LARGE_PAGE_MASK, ref_prot);
        set_pte((pte_t *)pmd, large_pte);
}      

static int
__change_page_attr(unsigned long address, unsigned long pfn, pgprot_t prot,
                                   pgprot_t ref_prot)
{ 
        pte_t *kpte; 
        struct page *kpte_page;
        unsigned kpte_flags;
        pgprot_t ref_prot2;
        kpte = lookup_address(address);
        if (!kpte) return 0;
        kpte_page = virt_to_page(((unsigned long)kpte) & PAGE_MASK);
        kpte_flags = pte_val(*kpte); 
        if (pgprot_val(prot) != pgprot_val(ref_prot)) { 
                if ((kpte_flags & _PAGE_PSE) == 0) { 
                        set_pte(kpte, pfn_pte(pfn, prot));
                } else {
                        /*
                         * split_large_page will take the reference for this
                         * change_page_attr on the split page.
                         */

                        struct page *split;
                        ref_prot2 = __pgprot(pgprot_val(pte_pgprot(*lookup_address(address))) & ~(1<<_PAGE_BIT_PSE));

                        split = split_large_page(address, prot, ref_prot2);
                        if (!split)
                                return -ENOMEM;
                        set_pte(kpte,mk_pte(split, ref_prot2));
                        kpte_page = split;
                }       
                page_private(kpte_page)++;
        } else if ((kpte_flags & _PAGE_PSE) == 0) { 
                set_pte(kpte, pfn_pte(pfn, ref_prot));
                BUG_ON(page_private(kpte_page) == 0);
                page_private(kpte_page)--;
        } else
                BUG();

        /* on x86-64 the direct mapping set at boot is not using 4k pages */
        /*
         * ..., but the XEN guest kernels (currently) do:
         * If the pte was reserved, it means it was created at boot
         * time (not via split_large_page) and in turn we must not
         * replace it with a large page.
         */
#ifndef CONFIG_XEN
        BUG_ON(PageReserved(kpte_page));
#else
        if (PageReserved(kpte_page))
                return 0;
#endif

        if (page_private(kpte_page) == 0) {
                save_page(kpte_page);
                revert_page(address, ref_prot);
        }
        return 0;
} 

/*
 * Change the page attributes of an page in the linear mapping.
 *
 * This should be used when a page is mapped with a different caching policy
 * than write-back somewhere - some CPUs do not like it when mappings with
 * different caching policies exist. This changes the page attributes of the
 * in kernel linear mapping too.
 * 
 * The caller needs to ensure that there are no conflicting mappings elsewhere.
 * This function only deals with the kernel linear map.
 * 
 * Caller must call global_flush_tlb() after this.
 */
int change_page_attr_addr(unsigned long address, int numpages, pgprot_t prot)
{
        int err = 0; 
        int i; 

        down_write(&init_mm.mmap_sem);
        for (i = 0; i < numpages; i++, address += PAGE_SIZE) {
                unsigned long pfn = __pa(address) >> PAGE_SHIFT;

                err = __change_page_attr(address, pfn, prot, PAGE_KERNEL);
                if (err) 
                        break; 
                /* Handle kernel mapping too which aliases part of the
                 * lowmem */
                if (__pa(address) < KERNEL_TEXT_SIZE) {
                        unsigned long addr2;
                        pgprot_t prot2 = prot;
                        addr2 = __START_KERNEL_map + __pa(address);
                        pgprot_val(prot2) &= ~_PAGE_NX;
                        err = __change_page_attr(addr2, pfn, prot2, PAGE_KERNEL_EXEC);
                } 
        }       
        up_write(&init_mm.mmap_sem); 
        return err;
}

/* Don't call this for MMIO areas that may not have a mem_map entry */
int change_page_attr(struct page *page, int numpages, pgprot_t prot)
{
        unsigned long addr = (unsigned long)page_address(page);
        return change_page_attr_addr(addr, numpages, prot);
}

void global_flush_tlb(void)
{ 
        struct page *dpage;

        down_read(&init_mm.mmap_sem);
        dpage = xchg(&deferred_pages, NULL);
        up_read(&init_mm.mmap_sem);

        flush_map((dpage && !dpage->lru.next) ? (unsigned long)page_address(dpage) : 0);
        while (dpage) {
                struct page *tmp = dpage;
                dpage = (struct page *)dpage->lru.next;
                ClearPagePrivate(tmp);
                __free_page(tmp);
        } 
} 

EXPORT_SYMBOL(change_page_attr);
EXPORT_SYMBOL(global_flush_tlb);