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tsb.c

/* arch/sparc64/mm/tsb.c
 *
 * Copyright (C) 2006 David S. Miller <davem@davemloft.net>
 */

#include <linux/kernel.h>
#include <asm/system.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);
                  membar_storeload_storestore();
            }
      }
}

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

      for (i = 0; i < mp->tlb_nr; i++) {
            unsigned long v = mp->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 mmu_gather *mp)
{
      struct mm_struct *mm = mp->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(mp, PAGE_SHIFT, base, nentries);

#ifdef CONFIG_HUGETLB_PAGE
      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(mp, HPAGE_SHIFT, base, nentries);
      }
#endif
      spin_unlock_irqrestore(&mm->context.lock, flags);
}

#if defined(CONFIG_SPARC64_PAGE_SIZE_8KB)
#define HV_PGSZ_IDX_BASE      HV_PGSZ_IDX_8K
#define HV_PGSZ_MASK_BASE     HV_PGSZ_MASK_8K
#elif defined(CONFIG_SPARC64_PAGE_SIZE_64KB)
#define HV_PGSZ_IDX_BASE      HV_PGSZ_IDX_64K
#define HV_PGSZ_MASK_BASE     HV_PGSZ_MASK_64K
#elif defined(CONFIG_SPARC64_PAGE_SIZE_512KB)
#define HV_PGSZ_IDX_BASE      HV_PGSZ_IDX_512K
#define HV_PGSZ_MASK_BASE     HV_PGSZ_MASK_512K
#elif defined(CONFIG_SPARC64_PAGE_SIZE_4MB)
#define HV_PGSZ_IDX_BASE      HV_PGSZ_IDX_4MB
#define HV_PGSZ_MASK_BASE     HV_PGSZ_MASK_4MB
#else
#error Broken base page size setting...
#endif

#ifdef CONFIG_HUGETLB_PAGE
#if defined(CONFIG_HUGETLB_PAGE_SIZE_64K)
#define HV_PGSZ_IDX_HUGE      HV_PGSZ_IDX_64K
#define HV_PGSZ_MASK_HUGE     HV_PGSZ_MASK_64K
#elif defined(CONFIG_HUGETLB_PAGE_SIZE_512K)
#define HV_PGSZ_IDX_HUGE      HV_PGSZ_IDX_512K
#define HV_PGSZ_MASK_HUGE     HV_PGSZ_MASK_512K
#elif defined(CONFIG_HUGETLB_PAGE_SIZE_4MB)
#define HV_PGSZ_IDX_HUGE      HV_PGSZ_IDX_4MB
#define HV_PGSZ_MASK_HUGE     HV_PGSZ_MASK_4MB
#else
#error Broken huge page size setting...
#endif
#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;
#ifdef CONFIG_HUGETLB_PAGE
            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;
#ifdef CONFIG_HUGETLB_PAGE
            case MM_TSB_HUGE:
                  hp->pgsz_mask = HV_PGSZ_MASK_HUGE;
                  break;
#endif
            default:
                  BUG();
            };
            hp->tsb_base = tsb_paddr;
            hp->resv = 0;
      }
}

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;

      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();
            }
      }
}

/* 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) {
            unsigned long n_entries = new_size / sizeof(struct tsb);

            n_entries = (n_entries * 3) / 4;
            if (n_entries > rss)
                  break;

            new_cache_index++;
      }

      if (new_size == max_tsb_size)
            new_rss_limit = ~0UL;
      else
            new_rss_limit = ((new_size / sizeof(struct tsb)) * 3) / 4;

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

      new_tsb = kmem_cache_alloc(tsb_caches[new_cache_index], gfp_flags);
      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.  */
            smp_tsb_sync(mm);

            /* 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)
{
#ifdef CONFIG_HUGETLB_PAGE
      unsigned long huge_pte_count;
#endif
      unsigned int i;

      spin_lock_init(&mm->context.lock);

      mm->context.sparc64_ctx_val = 0UL;

#ifdef CONFIG_HUGETLB_PAGE
      /* 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

      /* 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));

#ifdef CONFIG_HUGETLB_PAGE
      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;

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

      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);
}

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