source: trunk/packages/xen-3.1/xen-3.1/linux-2.6-xen-sparse/arch/i386/mm/pgtable-xen.c @ 34

/*
 *  linux/arch/i386/mm/pgtable.c
 */

#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/mm.h>
#include <linux/swap.h>
#include <linux/smp.h>
#include <linux/highmem.h>
#include <linux/slab.h>
#include <linux/pagemap.h>
#include <linux/spinlock.h>
#include <linux/module.h>

#include <asm/system.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
#include <asm/fixmap.h>
#include <asm/e820.h>
#include <asm/tlb.h>
#include <asm/tlbflush.h>
#include <asm/io.h>
#include <asm/mmu_context.h>

#include <xen/features.h>
#include <asm/hypervisor.h>

static void pgd_test_and_unpin(pgd_t *pgd);

void show_mem(void)
{
        int total = 0, reserved = 0;
        int shared = 0, cached = 0;
        int highmem = 0;
        struct page *page;
        pg_data_t *pgdat;
        unsigned long i;
        unsigned long flags;

        printk(KERN_INFO "Mem-info:\n");
        show_free_areas();
        printk(KERN_INFO "Free swap:       %6ldkB\n", nr_swap_pages<<(PAGE_SHIFT-10));
        for_each_online_pgdat(pgdat) {
                pgdat_resize_lock(pgdat, &flags);
                for (i = 0; i < pgdat->node_spanned_pages; ++i) {
                        page = pgdat_page_nr(pgdat, i);
                        total++;
                        if (PageHighMem(page))
                                highmem++;
                        if (PageReserved(page))
                                reserved++;
                        else if (PageSwapCache(page))
                                cached++;
                        else if (page_count(page))
                                shared += page_count(page) - 1;
                }
                pgdat_resize_unlock(pgdat, &flags);
        }
        printk(KERN_INFO "%d pages of RAM\n", total);
        printk(KERN_INFO "%d pages of HIGHMEM\n", highmem);
        printk(KERN_INFO "%d reserved pages\n", reserved);
        printk(KERN_INFO "%d pages shared\n", shared);
        printk(KERN_INFO "%d pages swap cached\n", cached);

        printk(KERN_INFO "%lu pages dirty\n", global_page_state(NR_FILE_DIRTY));
        printk(KERN_INFO "%lu pages writeback\n",
                                        global_page_state(NR_WRITEBACK));
        printk(KERN_INFO "%lu pages mapped\n", global_page_state(NR_FILE_MAPPED));
        printk(KERN_INFO "%lu pages slab\n", global_page_state(NR_SLAB));
        printk(KERN_INFO "%lu pages pagetables\n",
                                        global_page_state(NR_PAGETABLE));
}

/*
 * Associate a virtual page frame with a given physical page frame 
 * and protection flags for that frame.
 */ 
static void set_pte_pfn(unsigned long vaddr, unsigned long pfn, pgprot_t flags)
{
        pgd_t *pgd;
        pud_t *pud;
        pmd_t *pmd;
        pte_t *pte;

        pgd = swapper_pg_dir + pgd_index(vaddr);
        if (pgd_none(*pgd)) {
                BUG();
                return;
        }
        pud = pud_offset(pgd, vaddr);
        if (pud_none(*pud)) {
                BUG();
                return;
        }
        pmd = pmd_offset(pud, vaddr);
        if (pmd_none(*pmd)) {
                BUG();
                return;
        }
        pte = pte_offset_kernel(pmd, vaddr);
        if (pgprot_val(flags))
                /* <pfn,flags> stored as-is, to permit clearing entries */
                set_pte(pte, pfn_pte(pfn, flags));
        else
                pte_clear(&init_mm, vaddr, pte);

        /*
         * It's enough to flush this one mapping.
         * (PGE mappings get flushed as well)
         */
        __flush_tlb_one(vaddr);
}

/*
 * Associate a virtual page frame with a given physical page frame 
 * and protection flags for that frame.
 */ 
static void set_pte_pfn_ma(unsigned long vaddr, unsigned long pfn,
                           pgprot_t flags)
{
        pgd_t *pgd;
        pud_t *pud;
        pmd_t *pmd;
        pte_t *pte;

        pgd = swapper_pg_dir + pgd_index(vaddr);
        if (pgd_none(*pgd)) {
                BUG();
                return;
        }
        pud = pud_offset(pgd, vaddr);
        if (pud_none(*pud)) {
                BUG();
                return;
        }
        pmd = pmd_offset(pud, vaddr);
        if (pmd_none(*pmd)) {
                BUG();
                return;
        }
        pte = pte_offset_kernel(pmd, vaddr);
        if (pgprot_val(flags))
                /* <pfn,flags> stored as-is, to permit clearing entries */
                set_pte(pte, pfn_pte_ma(pfn, flags));
        else
                pte_clear(&init_mm, vaddr, pte);

        /*
         * It's enough to flush this one mapping.
         * (PGE mappings get flushed as well)
         */
        __flush_tlb_one(vaddr);
}

/*
 * Associate a large virtual page frame with a given physical page frame 
 * and protection flags for that frame. pfn is for the base of the page,
 * vaddr is what the page gets mapped to - both must be properly aligned. 
 * The pmd must already be instantiated. Assumes PAE mode.
 */ 
void set_pmd_pfn(unsigned long vaddr, unsigned long pfn, pgprot_t flags)
{
        pgd_t *pgd;
        pud_t *pud;
        pmd_t *pmd;

        if (vaddr & (PMD_SIZE-1)) {             /* vaddr is misaligned */
                printk(KERN_WARNING "set_pmd_pfn: vaddr misaligned\n");
                return; /* BUG(); */
        }
        if (pfn & (PTRS_PER_PTE-1)) {           /* pfn is misaligned */
                printk(KERN_WARNING "set_pmd_pfn: pfn misaligned\n");
                return; /* BUG(); */
        }
        pgd = swapper_pg_dir + pgd_index(vaddr);
        if (pgd_none(*pgd)) {
                printk(KERN_WARNING "set_pmd_pfn: pgd_none\n");
                return; /* BUG(); */
        }
        pud = pud_offset(pgd, vaddr);
        pmd = pmd_offset(pud, vaddr);
        set_pmd(pmd, pfn_pmd(pfn, flags));
        /*
         * It's enough to flush this one mapping.
         * (PGE mappings get flushed as well)
         */
        __flush_tlb_one(vaddr);
}

static int nr_fixmaps = 0;
unsigned long hypervisor_virt_start = HYPERVISOR_VIRT_START;
unsigned long __FIXADDR_TOP = (HYPERVISOR_VIRT_START - 2 * PAGE_SIZE);
EXPORT_SYMBOL(__FIXADDR_TOP);

void __init set_fixaddr_top(unsigned long top)
{
        BUG_ON(nr_fixmaps > 0);
        hypervisor_virt_start = top;
        __FIXADDR_TOP = hypervisor_virt_start - 2 * PAGE_SIZE;
}

void __set_fixmap (enum fixed_addresses idx, maddr_t phys, pgprot_t flags)
{
        unsigned long address = __fix_to_virt(idx);

        if (idx >= __end_of_fixed_addresses) {
                BUG();
                return;
        }
        switch (idx) {
        case FIX_WP_TEST:
#ifdef CONFIG_X86_F00F_BUG
        case FIX_F00F_IDT:
#endif
        case FIX_VDSO:
                set_pte_pfn(address, phys >> PAGE_SHIFT, flags);
                break;
        default:
                set_pte_pfn_ma(address, phys >> PAGE_SHIFT, flags);
                break;
        }
        nr_fixmaps++;
}

pte_t *pte_alloc_one_kernel(struct mm_struct *mm, unsigned long address)
{
        pte_t *pte = (pte_t *)__get_free_page(GFP_KERNEL|__GFP_REPEAT|__GFP_ZERO);
        if (pte)
                make_lowmem_page_readonly(pte, XENFEAT_writable_page_tables);
        return pte;
}

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

#ifdef CONFIG_HIGHPTE
        pte = alloc_pages(GFP_KERNEL|__GFP_HIGHMEM|__GFP_REPEAT|__GFP_ZERO, 0);
#else
        pte = alloc_pages(GFP_KERNEL|__GFP_REPEAT|__GFP_ZERO, 0);
#endif
        if (pte) {
                SetPageForeign(pte, pte_free);
                init_page_count(pte);
        }
        return pte;
}

void pte_free(struct page *pte)
{
        unsigned long pfn = page_to_pfn(pte);

        if (!PageHighMem(pte)) {
                unsigned long va = (unsigned long)__va(pfn << PAGE_SHIFT);

                if (!pte_write(*virt_to_ptep(va)))
                        if (HYPERVISOR_update_va_mapping(
                                va, pfn_pte(pfn, PAGE_KERNEL), 0))
                                BUG();
        } else
                clear_bit(PG_pinned, &pte->flags);

        ClearPageForeign(pte);
        init_page_count(pte);

        __free_page(pte);
}

void pmd_ctor(void *pmd, kmem_cache_t *cache, unsigned long flags)
{
        memset(pmd, 0, PTRS_PER_PMD*sizeof(pmd_t));
}

/*
 * List of all pgd's needed for non-PAE so it can invalidate entries
 * in both cached and uncached pgd's; not needed for PAE since the
 * kernel pmd is shared. If PAE were not to share the pmd a similar
 * tactic would be needed. This is essentially codepath-based locking
 * against pageattr.c; it is the unique case in which a valid change
 * of kernel pagetables can't be lazily synchronized by vmalloc faults.
 * vmalloc faults work because attached pagetables are never freed.
 * The locking scheme was chosen on the basis of manfred's
 * recommendations and having no core impact whatsoever.
 * -- wli
 */
DEFINE_SPINLOCK(pgd_lock);
struct page *pgd_list;

static inline void pgd_list_add(pgd_t *pgd)
{
        struct page *page = virt_to_page(pgd);
        page->index = (unsigned long)pgd_list;
        if (pgd_list)
                set_page_private(pgd_list, (unsigned long)&page->index);
        pgd_list = page;
        set_page_private(page, (unsigned long)&pgd_list);
}

static inline void pgd_list_del(pgd_t *pgd)
{
        struct page *next, **pprev, *page = virt_to_page(pgd);
        next = (struct page *)page->index;
        pprev = (struct page **)page_private(page);
        *pprev = next;
        if (next)
                set_page_private(next, (unsigned long)pprev);
}

void pgd_ctor(void *pgd, kmem_cache_t *cache, unsigned long unused)
{
        unsigned long flags;

        if (PTRS_PER_PMD > 1) {
                if (HAVE_SHARED_KERNEL_PMD)
                        clone_pgd_range((pgd_t *)pgd + USER_PTRS_PER_PGD,
                                        swapper_pg_dir + USER_PTRS_PER_PGD,
                                        KERNEL_PGD_PTRS);
        } else {
                spin_lock_irqsave(&pgd_lock, flags);
                clone_pgd_range((pgd_t *)pgd + USER_PTRS_PER_PGD,
                                swapper_pg_dir + USER_PTRS_PER_PGD,
                                KERNEL_PGD_PTRS);
                memset(pgd, 0, USER_PTRS_PER_PGD*sizeof(pgd_t));
                pgd_list_add(pgd);
                spin_unlock_irqrestore(&pgd_lock, flags);
        }
}

/* never called when PTRS_PER_PMD > 1 */
void pgd_dtor(void *pgd, kmem_cache_t *cache, unsigned long unused)
{
        unsigned long flags; /* can be called from interrupt context */

        spin_lock_irqsave(&pgd_lock, flags);
        pgd_list_del(pgd);
        spin_unlock_irqrestore(&pgd_lock, flags);

        pgd_test_and_unpin(pgd);
}

pgd_t *pgd_alloc(struct mm_struct *mm)
{
        int i;
        pgd_t *pgd = kmem_cache_alloc(pgd_cache, GFP_KERNEL);
        pmd_t **pmd;
        unsigned long flags;

        pgd_test_and_unpin(pgd);

        if (PTRS_PER_PMD == 1 || !pgd)
                return pgd;

        if (HAVE_SHARED_KERNEL_PMD) {
                for (i = 0; i < USER_PTRS_PER_PGD; ++i) {
                        pmd_t *pmd = kmem_cache_alloc(pmd_cache, GFP_KERNEL);
                        if (!pmd)
                                goto out_oom;
                        set_pgd(&pgd[i], __pgd(1 + __pa(pmd)));
                }
                return pgd;
        }

        /*
         * We can race save/restore (if we sleep during a GFP_KERNEL memory
         * allocation). We therefore store virtual addresses of pmds as they
         * do not change across save/restore, and poke the machine addresses
         * into the pgdir under the pgd_lock.
         */
        pmd = kmalloc(PTRS_PER_PGD * sizeof(pmd_t *), GFP_KERNEL);
        if (!pmd) {
                kmem_cache_free(pgd_cache, pgd);
                return NULL;
        }

        /* Allocate pmds, remember virtual addresses. */
        for (i = 0; i < PTRS_PER_PGD; ++i) {
                pmd[i] = kmem_cache_alloc(pmd_cache, GFP_KERNEL);
                if (!pmd[i])
                        goto out_oom;
        }

        spin_lock_irqsave(&pgd_lock, flags);

        /* Protect against save/restore: move below 4GB under pgd_lock. */
        if (!xen_feature(XENFEAT_pae_pgdir_above_4gb)) {
                int rc = xen_create_contiguous_region(
                        (unsigned long)pgd, 0, 32);
                if (rc) {
                        spin_unlock_irqrestore(&pgd_lock, flags);
                        goto out_oom;
                }
        }

        /* Copy kernel pmd contents and write-protect the new pmds. */
        for (i = USER_PTRS_PER_PGD; i < PTRS_PER_PGD; i++) {
                unsigned long v = (unsigned long)i << PGDIR_SHIFT;
                pgd_t *kpgd = pgd_offset_k(v);
                pud_t *kpud = pud_offset(kpgd, v);
                pmd_t *kpmd = pmd_offset(kpud, v);
                memcpy(pmd[i], kpmd, PAGE_SIZE);
                make_lowmem_page_readonly(
                        pmd[i], XENFEAT_writable_page_tables);
        }

        /* It is safe to poke machine addresses of pmds under the pmd_lock. */
        for (i = 0; i < PTRS_PER_PGD; i++)
                set_pgd(&pgd[i], __pgd(1 + __pa(pmd[i])));

        /* Ensure this pgd gets picked up and pinned on save/restore. */
        pgd_list_add(pgd);

        spin_unlock_irqrestore(&pgd_lock, flags);

        kfree(pmd);

        return pgd;

out_oom:
        if (HAVE_SHARED_KERNEL_PMD) {
                for (i--; i >= 0; i--)
                        kmem_cache_free(pmd_cache,
                                        (void *)__va(pgd_val(pgd[i])-1));
        } else {
                for (i--; i >= 0; i--)
                        kmem_cache_free(pmd_cache, pmd[i]);
                kfree(pmd);
        }
        kmem_cache_free(pgd_cache, pgd);
        return NULL;
}

void pgd_free(pgd_t *pgd)
{
        int i;

        /*
         * After this the pgd should not be pinned for the duration of this
         * function's execution. We should never sleep and thus never race:
         *  1. User pmds will not become write-protected under our feet due
         *     to a concurrent mm_pin_all().
         *  2. The machine addresses in PGD entries will not become invalid
         *     due to a concurrent save/restore.
         */
        pgd_test_and_unpin(pgd);

        /* in the PAE case user pgd entries are overwritten before usage */
        if (PTRS_PER_PMD > 1) {
                for (i = 0; i < USER_PTRS_PER_PGD; ++i) {
                        pmd_t *pmd = (void *)__va(pgd_val(pgd[i])-1);
                        kmem_cache_free(pmd_cache, pmd);
                }

                if (!HAVE_SHARED_KERNEL_PMD) {
                        unsigned long flags;
                        spin_lock_irqsave(&pgd_lock, flags);
                        pgd_list_del(pgd);
                        spin_unlock_irqrestore(&pgd_lock, flags);

                        for (i = USER_PTRS_PER_PGD; i < PTRS_PER_PGD; i++) {
                                pmd_t *pmd = (void *)__va(pgd_val(pgd[i])-1);
                                make_lowmem_page_writable(
                                        pmd, XENFEAT_writable_page_tables);
                                memset(pmd, 0, PTRS_PER_PMD*sizeof(pmd_t));
                                kmem_cache_free(pmd_cache, pmd);
                        }

                        if (!xen_feature(XENFEAT_pae_pgdir_above_4gb))
                                xen_destroy_contiguous_region(
                                        (unsigned long)pgd, 0);
                }
        }

        /* in the non-PAE case, free_pgtables() clears user pgd entries */
        kmem_cache_free(pgd_cache, pgd);
}

void make_lowmem_page_readonly(void *va, unsigned int feature)
{
        pte_t *pte;
        int rc;

        if (xen_feature(feature))
                return;

        pte = virt_to_ptep(va);
        rc = HYPERVISOR_update_va_mapping(
                (unsigned long)va, pte_wrprotect(*pte), 0);
        BUG_ON(rc);
}

void make_lowmem_page_writable(void *va, unsigned int feature)
{
        pte_t *pte;
        int rc;

        if (xen_feature(feature))
                return;

        pte = virt_to_ptep(va);
        rc = HYPERVISOR_update_va_mapping(
                (unsigned long)va, pte_mkwrite(*pte), 0);
        BUG_ON(rc);
}

void make_page_readonly(void *va, unsigned int feature)
{
        pte_t *pte;
        int rc;

        if (xen_feature(feature))
                return;

        pte = virt_to_ptep(va);
        rc = HYPERVISOR_update_va_mapping(
                (unsigned long)va, pte_wrprotect(*pte), 0);
        if (rc) /* fallback? */
                xen_l1_entry_update(pte, pte_wrprotect(*pte));
        if ((unsigned long)va >= (unsigned long)high_memory) {
                unsigned long pfn = pte_pfn(*pte);
#ifdef CONFIG_HIGHMEM
                if (pfn >= highstart_pfn)
                        kmap_flush_unused(); /* flush stale writable kmaps */
                else
#endif
                        make_lowmem_page_readonly(
                                phys_to_virt(pfn << PAGE_SHIFT), feature); 
        }
}

void make_page_writable(void *va, unsigned int feature)
{
        pte_t *pte;
        int rc;

        if (xen_feature(feature))
                return;

        pte = virt_to_ptep(va);
        rc = HYPERVISOR_update_va_mapping(
                (unsigned long)va, pte_mkwrite(*pte), 0);
        if (rc) /* fallback? */
                xen_l1_entry_update(pte, pte_mkwrite(*pte));
        if ((unsigned long)va >= (unsigned long)high_memory) {
                unsigned long pfn = pte_pfn(*pte); 
#ifdef CONFIG_HIGHMEM
                if (pfn < highstart_pfn)
#endif
                        make_lowmem_page_writable(
                                phys_to_virt(pfn << PAGE_SHIFT), feature);
        }
}

void make_pages_readonly(void *va, unsigned int nr, unsigned int feature)
{
        if (xen_feature(feature))
                return;

        while (nr-- != 0) {
                make_page_readonly(va, feature);
                va = (void *)((unsigned long)va + PAGE_SIZE);
        }
}

void make_pages_writable(void *va, unsigned int nr, unsigned int feature)
{
        if (xen_feature(feature))
                return;

        while (nr-- != 0) {
                make_page_writable(va, feature);
                va = (void *)((unsigned long)va + PAGE_SIZE);
        }
}

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

        if (PageHighMem(page)) {
                if (pgprot_val(flags) & _PAGE_RW)
                        clear_bit(PG_pinned, &page->flags);
                else
                        set_bit(PG_pinned, &page->flags);
        } else {
                rc = HYPERVISOR_update_va_mapping(
                        (unsigned long)__va(pfn << PAGE_SHIFT),
                        pfn_pte(pfn, flags), 0);
                if (rc)
                        BUG();
        }
}

static void pgd_walk(pgd_t *pgd_base, pgprot_t flags)
{
        pgd_t *pgd = pgd_base;
        pud_t *pud;
        pmd_t *pmd;
        int    g, u, m, rc;

        if (xen_feature(XENFEAT_auto_translated_physmap))
                return;

        for (g = 0; g < USER_PTRS_PER_PGD; g++, pgd++) {
                if (pgd_none(*pgd))
                        continue;
                pud = pud_offset(pgd, 0);
                if (PTRS_PER_PUD > 1) /* not folded */
                        pgd_walk_set_prot(virt_to_page(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 */
                                pgd_walk_set_prot(virt_to_page(pmd),flags);
                        for (m = 0; m < PTRS_PER_PMD; m++, pmd++) {
                                if (pmd_none(*pmd))
                                        continue;
                                pgd_walk_set_prot(pmd_page(*pmd),flags);
                        }
                }
        }

        rc = HYPERVISOR_update_va_mapping(
                (unsigned long)pgd_base,
                pfn_pte(virt_to_phys(pgd_base)>>PAGE_SHIFT, flags),
                UVMF_TLB_FLUSH);
        if (rc)
                BUG();
}

static void __pgd_pin(pgd_t *pgd)
{
        pgd_walk(pgd, PAGE_KERNEL_RO);
        kmap_flush_unused();
        xen_pgd_pin(__pa(pgd));
        set_bit(PG_pinned, &virt_to_page(pgd)->flags);
}

static void __pgd_unpin(pgd_t *pgd)
{
        xen_pgd_unpin(__pa(pgd));
        pgd_walk(pgd, PAGE_KERNEL);
        clear_bit(PG_pinned, &virt_to_page(pgd)->flags);
}

static void pgd_test_and_unpin(pgd_t *pgd)
{
        if (test_bit(PG_pinned, &virt_to_page(pgd)->flags))
                __pgd_unpin(pgd);
}

void mm_pin(struct mm_struct *mm)
{
        if (xen_feature(XENFEAT_writable_page_tables))
                return;
        spin_lock(&mm->page_table_lock);
        __pgd_pin(mm->pgd);
        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);
        __pgd_unpin(mm->pgd);
        spin_unlock(&mm->page_table_lock);
}

void mm_pin_all(void)
{
        struct page *page;
        unsigned long flags;

        if (xen_feature(XENFEAT_writable_page_tables))
                return;

        /*
         * Allow uninterrupted access to the pgd_list. Also protects
         * __pgd_pin() by disabling preemption.
         * All other CPUs must be at a safe point (e.g., in stop_machine
         * or offlined entirely).
         */
        spin_lock_irqsave(&pgd_lock, flags);
        for (page = pgd_list; page; page = (struct page *)page->index) {
                if (!test_bit(PG_pinned, &page->flags))
                        __pgd_pin((pgd_t *)page_address(page));
        }
        spin_unlock_irqrestore(&pgd_lock, flags);
}

void _arch_dup_mmap(struct mm_struct *mm)
{
        if (!test_bit(PG_pinned, &virt_to_page(mm->pgd)->flags))
                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 (test_bit(PG_pinned, &virt_to_page(mm->pgd)->flags) &&
            (atomic_read(&mm->mm_count) == 1) &&
            !mm->context.has_foreign_mappings)
                mm_unpin(mm);
}