tsb.c

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/* arch/sparc64/mm/tsb.c
 *
 * Copyright (C) 2006, 2008 David S. Miller <[email protected]>
 */

#include <linux/kernel.h>
#include <linux/preempt.h>
#include <linux/slab.h>
#include <asm/page.h>
#include <asm/tlbflush.h>
#include <asm/tlb.h>
#include <asm/mmu_context.h>
#include <asm/pgtable.h>
#include <asm/tsb.h>
#include <asm/oplib.h>

extern struct tsb swapper_tsb[KERNEL_TSB_NENTRIES];

static inline unsigned long tsb_hash(unsigned long vaddr, unsigned long hash_shift, unsigned long nentries)
{
    vaddr >>= hash_shift;
    return vaddr & (nentries - 1);
}

static inline int tag_compare(unsigned long tag, unsigned long vaddr)
{
    return (tag == (vaddr >> 22));
}

/* TSB flushes need only occur on the processor initiating the address
 * space modification, not on each cpu the address space has run on.
 * Only the TLB flush needs that treatment.
 */

void flush_tsb_kernel_range(unsigned long start, unsigned long end)
{
    unsigned long v;

    for (v = start; v < end; v += PAGE_SIZE) {
        unsigned long hash = tsb_hash(v, PAGE_SHIFT,
                          KERNEL_TSB_NENTRIES);
        struct tsb *ent = &swapper_tsb[hash];

        if (tag_compare(ent->tag, v))
            ent->tag = (1UL << TSB_TAG_INVALID_BIT);
    }
}

static void __flush_tsb_one(struct tlb_batch *tb, unsigned long hash_shift,
                unsigned long tsb, unsigned long nentries)
{
    unsigned long i;

    for (i = 0; i < tb->tlb_nr; i++) {
        unsigned long v = tb->vaddrs[i];
        unsigned long tag, ent, hash;

        v &= ~0x1UL;

        hash = tsb_hash(v, hash_shift, nentries);
        ent = tsb + (hash * sizeof(struct tsb));
        tag = (v >> 22UL);

        tsb_flush(ent, tag);
    }
}

void flush_tsb_user(struct tlb_batch *tb)
{
    struct mm_struct *mm = tb->mm;
    unsigned long nentries, base, flags;

    spin_lock_irqsave(&mm->context.lock, flags);

    base = (unsigned long) mm->context.tsb_block[MM_TSB_BASE].tsb;
    nentries = mm->context.tsb_block[MM_TSB_BASE].tsb_nentries;
    if (tlb_type == cheetah_plus || tlb_type == hypervisor)
        base = __pa(base);
    __flush_tsb_one(tb, PAGE_SHIFT, base, nentries);

#if defined(CONFIG_HUGETLB_PAGE) || defined(CONFIG_TRANSPARENT_HUGEPAGE)
    if (mm->context.tsb_block[MM_TSB_HUGE].tsb) {
        base = (unsigned long) mm->context.tsb_block[MM_TSB_HUGE].tsb;
        nentries = mm->context.tsb_block[MM_TSB_HUGE].tsb_nentries;
        if (tlb_type == cheetah_plus || tlb_type == hypervisor)
            base = __pa(base);
        __flush_tsb_one(tb, HPAGE_SHIFT, base, nentries);
    }
#endif
    spin_unlock_irqrestore(&mm->context.lock, flags);
}

#define HV_PGSZ_IDX_BASE    HV_PGSZ_IDX_8K
#define HV_PGSZ_MASK_BASE   HV_PGSZ_MASK_8K

#if defined(CONFIG_HUGETLB_PAGE) || defined(CONFIG_TRANSPARENT_HUGEPAGE)
#define HV_PGSZ_IDX_HUGE    HV_PGSZ_IDX_4MB
#define HV_PGSZ_MASK_HUGE   HV_PGSZ_MASK_4MB
#endif

static void setup_tsb_params(struct mm_struct *mm, unsigned long tsb_idx, unsigned long tsb_bytes)
{
    unsigned long tsb_reg, base, tsb_paddr;
    unsigned long page_sz, tte;

    mm->context.tsb_block[tsb_idx].tsb_nentries =
        tsb_bytes / sizeof(struct tsb);

    base = TSBMAP_BASE;
    tte = pgprot_val(PAGE_KERNEL_LOCKED);
    tsb_paddr = __pa(mm->context.tsb_block[tsb_idx].tsb);
    BUG_ON(tsb_paddr & (tsb_bytes - 1UL));

    /* Use the smallest page size that can map the whole TSB
     * in one TLB entry.
     */
    switch (tsb_bytes) {
    case 8192 << 0:
        tsb_reg = 0x0UL;
#ifdef DCACHE_ALIASING_POSSIBLE
        base += (tsb_paddr & 8192);
#endif
        page_sz = 8192;
        break;

    case 8192 << 1:
        tsb_reg = 0x1UL;
        page_sz = 64 * 1024;
        break;

    case 8192 << 2:
        tsb_reg = 0x2UL;
        page_sz = 64 * 1024;
        break;

    case 8192 << 3:
        tsb_reg = 0x3UL;
        page_sz = 64 * 1024;
        break;

    case 8192 << 4:
        tsb_reg = 0x4UL;
        page_sz = 512 * 1024;
        break;

    case 8192 << 5:
        tsb_reg = 0x5UL;
        page_sz = 512 * 1024;
        break;

    case 8192 << 6:
        tsb_reg = 0x6UL;
        page_sz = 512 * 1024;
        break;

    case 8192 << 7:
        tsb_reg = 0x7UL;
        page_sz = 4 * 1024 * 1024;
        break;

    default:
        printk(KERN_ERR "TSB[%s:%d]: Impossible TSB size %lu, killing process.\n",
               current->comm, current->pid, tsb_bytes);
        do_exit(SIGSEGV);
    }
    tte |= pte_sz_bits(page_sz);

    if (tlb_type == cheetah_plus || tlb_type == hypervisor) {
        /* Physical mapping, no locked TLB entry for TSB.  */
        tsb_reg |= tsb_paddr;

        mm->context.tsb_block[tsb_idx].tsb_reg_val = tsb_reg;
        mm->context.tsb_block[tsb_idx].tsb_map_vaddr = 0;
        mm->context.tsb_block[tsb_idx].tsb_map_pte = 0;
    } else {
        tsb_reg |= base;
        tsb_reg |= (tsb_paddr & (page_sz - 1UL));
        tte |= (tsb_paddr & ~(page_sz - 1UL));

        mm->context.tsb_block[tsb_idx].tsb_reg_val = tsb_reg;
        mm->context.tsb_block[tsb_idx].tsb_map_vaddr = base;
        mm->context.tsb_block[tsb_idx].tsb_map_pte = tte;
    }

    /* Setup the Hypervisor TSB descriptor.  */
    if (tlb_type == hypervisor) {
        struct hv_tsb_descr *hp = &mm->context.tsb_descr[tsb_idx];

        switch (tsb_idx) {
        case MM_TSB_BASE:
            hp->pgsz_idx = HV_PGSZ_IDX_BASE;
            break;
#if defined(CONFIG_HUGETLB_PAGE) || defined(CONFIG_TRANSPARENT_HUGEPAGE)
        case MM_TSB_HUGE:
            hp->pgsz_idx = HV_PGSZ_IDX_HUGE;
            break;
#endif
        default:
            BUG();
        }
        hp->assoc = 1;
        hp->num_ttes = tsb_bytes / 16;
        hp->ctx_idx = 0;
        switch (tsb_idx) {
        case MM_TSB_BASE:
            hp->pgsz_mask = HV_PGSZ_MASK_BASE;
            break;
#if defined(CONFIG_HUGETLB_PAGE) || defined(CONFIG_TRANSPARENT_HUGEPAGE)
        case MM_TSB_HUGE:
            hp->pgsz_mask = HV_PGSZ_MASK_HUGE;
            break;
#endif
        default:
            BUG();
        }
        hp->tsb_base = tsb_paddr;
        hp->resv = 0;
    }
}

struct kmem_cache *pgtable_cache __read_mostly;

static struct kmem_cache *tsb_caches[8] __read_mostly;

static const char *tsb_cache_names[8] = {
    "tsb_8KB",
    "tsb_16KB",
    "tsb_32KB",
    "tsb_64KB",
    "tsb_128KB",
    "tsb_256KB",
    "tsb_512KB",
    "tsb_1MB",
};

void __init pgtable_cache_init(void)
{
    unsigned long i;

    pgtable_cache = kmem_cache_create("pgtable_cache",
                      PAGE_SIZE, PAGE_SIZE,
                      0,
                      _clear_page);
    if (!pgtable_cache) {
        prom_printf("pgtable_cache_init(): Could not create!\n");
        prom_halt();
    }

    for (i = 0; i < 8; i++) {
        unsigned long size = 8192 << i;
        const char *name = tsb_cache_names[i];

        tsb_caches[i] = kmem_cache_create(name,
                          size, size,
                          0, NULL);
        if (!tsb_caches[i]) {
            prom_printf("Could not create %s cache\n", name);
            prom_halt();
        }
    }
}

int sysctl_tsb_ratio = -2;

static unsigned long tsb_size_to_rss_limit(unsigned long new_size)
{
    unsigned long num_ents = (new_size / sizeof(struct tsb));

    if (sysctl_tsb_ratio < 0)
        return num_ents - (num_ents >> -sysctl_tsb_ratio);
    else
        return num_ents + (num_ents >> sysctl_tsb_ratio);
}

/* When the RSS of an address space exceeds tsb_rss_limit for a TSB,
 * do_sparc64_fault() invokes this routine to try and grow it.
 *
 * When we reach the maximum TSB size supported, we stick ~0UL into
 * tsb_rss_limit for that TSB so the grow checks in do_sparc64_fault()
 * will not trigger any longer.
 *
 * The TSB can be anywhere from 8K to 1MB in size, in increasing powers
 * of two.  The TSB must be aligned to it's size, so f.e. a 512K TSB
 * must be 512K aligned.  It also must be physically contiguous, so we
 * cannot use vmalloc().
 *
 * The idea here is to grow the TSB when the RSS of the process approaches
 * the number of entries that the current TSB can hold at once.  Currently,
 * we trigger when the RSS hits 3/4 of the TSB capacity.
 */
void tsb_grow(struct mm_struct *mm, unsigned long tsb_index, unsigned long rss)
{
    unsigned long max_tsb_size = 1 * 1024 * 1024;
    unsigned long new_size, old_size, flags;
    struct tsb *old_tsb, *new_tsb;
    unsigned long new_cache_index, old_cache_index;
    unsigned long new_rss_limit;
    gfp_t gfp_flags;

    if (max_tsb_size > (PAGE_SIZE << MAX_ORDER))
        max_tsb_size = (PAGE_SIZE << MAX_ORDER);

    new_cache_index = 0;
    for (new_size = 8192; new_size < max_tsb_size; new_size <<= 1UL) {
        new_rss_limit = tsb_size_to_rss_limit(new_size);
        if (new_rss_limit > rss)
            break;
        new_cache_index++;
    }

    if (new_size == max_tsb_size)
        new_rss_limit = ~0UL;

retry_tsb_alloc:
    gfp_flags = GFP_KERNEL;
    if (new_size > (PAGE_SIZE * 2))
        gfp_flags = __GFP_NOWARN | __GFP_NORETRY;

    new_tsb = kmem_cache_alloc_node(tsb_caches[new_cache_index],
                    gfp_flags, numa_node_id());
    if (unlikely(!new_tsb)) {
        /* Not being able to fork due to a high-order TSB
         * allocation failure is very bad behavior.  Just back
         * down to a 0-order allocation and force no TSB
         * growing for this address space.
         */
        if (mm->context.tsb_block[tsb_index].tsb == NULL &&
            new_cache_index > 0) {
            new_cache_index = 0;
            new_size = 8192;
            new_rss_limit = ~0UL;
            goto retry_tsb_alloc;
        }

        /* If we failed on a TSB grow, we are under serious
         * memory pressure so don't try to grow any more.
         */
        if (mm->context.tsb_block[tsb_index].tsb != NULL)
            mm->context.tsb_block[tsb_index].tsb_rss_limit = ~0UL;
        return;
    }

    /* Mark all tags as invalid.  */
    tsb_init(new_tsb, new_size);

    /* Ok, we are about to commit the changes.  If we are
     * growing an existing TSB the locking is very tricky,
     * so WATCH OUT!
     *
     * We have to hold mm->context.lock while committing to the
     * new TSB, this synchronizes us with processors in
     * flush_tsb_user() and switch_mm() for this address space.
     *
     * But even with that lock held, processors run asynchronously
     * accessing the old TSB via TLB miss handling.  This is OK
     * because those actions are just propagating state from the
     * Linux page tables into the TSB, page table mappings are not
     * being changed.  If a real fault occurs, the processor will
     * synchronize with us when it hits flush_tsb_user(), this is
     * also true for the case where vmscan is modifying the page
     * tables.  The only thing we need to be careful with is to
     * skip any locked TSB entries during copy_tsb().
     *
     * When we finish committing to the new TSB, we have to drop
     * the lock and ask all other cpus running this address space
     * to run tsb_context_switch() to see the new TSB table.
     */
    spin_lock_irqsave(&mm->context.lock, flags);

    old_tsb = mm->context.tsb_block[tsb_index].tsb;
    old_cache_index =
        (mm->context.tsb_block[tsb_index].tsb_reg_val & 0x7UL);
    old_size = (mm->context.tsb_block[tsb_index].tsb_nentries *
            sizeof(struct tsb));


    /* Handle multiple threads trying to grow the TSB at the same time.
     * One will get in here first, and bump the size and the RSS limit.
     * The others will get in here next and hit this check.
     */
    if (unlikely(old_tsb &&
             (rss < mm->context.tsb_block[tsb_index].tsb_rss_limit))) {
        spin_unlock_irqrestore(&mm->context.lock, flags);

        kmem_cache_free(tsb_caches[new_cache_index], new_tsb);
        return;
    }

    mm->context.tsb_block[tsb_index].tsb_rss_limit = new_rss_limit;

    if (old_tsb) {
        extern void copy_tsb(unsigned long old_tsb_base,
                     unsigned long old_tsb_size,
                     unsigned long new_tsb_base,
                     unsigned long new_tsb_size);
        unsigned long old_tsb_base = (unsigned long) old_tsb;
        unsigned long new_tsb_base = (unsigned long) new_tsb;

        if (tlb_type == cheetah_plus || tlb_type == hypervisor) {
            old_tsb_base = __pa(old_tsb_base);
            new_tsb_base = __pa(new_tsb_base);
        }
        copy_tsb(old_tsb_base, old_size, new_tsb_base, new_size);
    }

    mm->context.tsb_block[tsb_index].tsb = new_tsb;
    setup_tsb_params(mm, tsb_index, new_size);

    spin_unlock_irqrestore(&mm->context.lock, flags);

    /* If old_tsb is NULL, we're being invoked for the first time
     * from init_new_context().
     */
    if (old_tsb) {
        /* Reload it on the local cpu.  */
        tsb_context_switch(mm);

        /* Now force other processors to do the same.  */
        preempt_disable();
        smp_tsb_sync(mm);
        preempt_enable();

        /* Now it is safe to free the old tsb.  */
        kmem_cache_free(tsb_caches[old_cache_index], old_tsb);
    }
}

int init_new_context(struct task_struct *tsk, struct mm_struct *mm)
{
#if defined(CONFIG_HUGETLB_PAGE) || defined(CONFIG_TRANSPARENT_HUGEPAGE)
    unsigned long huge_pte_count;
#endif
    unsigned int i;

    spin_lock_init(&mm->context.lock);

    mm->context.sparc64_ctx_val = 0UL;

#if defined(CONFIG_HUGETLB_PAGE) || defined(CONFIG_TRANSPARENT_HUGEPAGE)
    /* We reset it to zero because the fork() page copying
     * will re-increment the counters as the parent PTEs are
     * copied into the child address space.
     */
    huge_pte_count = mm->context.huge_pte_count;
    mm->context.huge_pte_count = 0;
#endif

    mm->context.pgtable_page = NULL;

    /* copy_mm() copies over the parent's mm_struct before calling
     * us, so we need to zero out the TSB pointer or else tsb_grow()
     * will be confused and think there is an older TSB to free up.
     */
    for (i = 0; i < MM_NUM_TSBS; i++)
        mm->context.tsb_block[i].tsb = NULL;

    /* If this is fork, inherit the parent's TSB size.  We would
     * grow it to that size on the first page fault anyways.
     */
    tsb_grow(mm, MM_TSB_BASE, get_mm_rss(mm));

#if defined(CONFIG_HUGETLB_PAGE) || defined(CONFIG_TRANSPARENT_HUGEPAGE)
    if (unlikely(huge_pte_count))
        tsb_grow(mm, MM_TSB_HUGE, huge_pte_count);
#endif

    if (unlikely(!mm->context.tsb_block[MM_TSB_BASE].tsb))
        return -ENOMEM;

    return 0;
}

static void tsb_destroy_one(struct tsb_config *tp)
{
    unsigned long cache_index;

    if (!tp->tsb)
        return;
    cache_index = tp->tsb_reg_val & 0x7UL;
    kmem_cache_free(tsb_caches[cache_index], tp->tsb);
    tp->tsb = NULL;
    tp->tsb_reg_val = 0UL;
}

void destroy_context(struct mm_struct *mm)
{
    unsigned long flags, i;
    struct page *page;

    for (i = 0; i < MM_NUM_TSBS; i++)
        tsb_destroy_one(&mm->context.tsb_block[i]);

    page = mm->context.pgtable_page;
    if (page && put_page_testzero(page)) {
        pgtable_page_dtor(page);
        free_hot_cold_page(page, 0);
    }

    spin_lock_irqsave(&ctx_alloc_lock, flags);

    if (CTX_VALID(mm->context)) {
        unsigned long nr = CTX_NRBITS(mm->context);
        mmu_context_bmap[nr>>6] &= ~(1UL << (nr & 63));
    }

    spin_unlock_irqrestore(&ctx_alloc_lock, flags);
}