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uncached.c

/*
 * Copyright (C) 2001-2008 Silicon Graphics, Inc.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of version 2 of the GNU General Public License
 * as published by the Free Software Foundation.
 *
 * A simple uncached page allocator using the generic allocator. This
 * allocator first utilizes the spare (spill) pages found in the EFI
 * memmap and will then start converting cached pages to uncached ones
 * at a granule at a time. Node awareness is implemented by having a
 * pool of pages per node.
 */

#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/slab.h>
#include <linux/efi.h>
#include <linux/genalloc.h>
#include <asm/page.h>
#include <asm/pal.h>
#include <asm/system.h>
#include <asm/pgtable.h>
#include <asm/atomic.h>
#include <asm/tlbflush.h>
#include <asm/sn/arch.h>


extern void __init efi_memmap_walk_uc(efi_freemem_callback_t, void *);

struct uncached_pool {
      struct gen_pool *pool;
      struct mutex add_chunk_mutex; /* serialize adding a converted chunk */
      int nchunks_added;            /* #of converted chunks added to pool */
      atomic_t status;        /* smp called function's return status*/
};

#define MAX_CONVERTED_CHUNKS_PER_NODE     2

struct uncached_pool uncached_pools[MAX_NUMNODES];


static void uncached_ipi_visibility(void *data)
{
      int status;
      struct uncached_pool *uc_pool = (struct uncached_pool *)data;

      status = ia64_pal_prefetch_visibility(PAL_VISIBILITY_PHYSICAL);
      if ((status != PAL_VISIBILITY_OK) &&
          (status != PAL_VISIBILITY_OK_REMOTE_NEEDED))
            atomic_inc(&uc_pool->status);
}


static void uncached_ipi_mc_drain(void *data)
{
      int status;
      struct uncached_pool *uc_pool = (struct uncached_pool *)data;

      status = ia64_pal_mc_drain();
      if (status != PAL_STATUS_SUCCESS)
            atomic_inc(&uc_pool->status);
}


/*
 * Add a new chunk of uncached memory pages to the specified pool.
 *
 * @pool: pool to add new chunk of uncached memory to
 * @nid: node id of node to allocate memory from, or -1
 *
 * This is accomplished by first allocating a granule of cached memory pages
 * and then converting them to uncached memory pages.
 */
static int uncached_add_chunk(struct uncached_pool *uc_pool, int nid)
{
      struct page *page;
      int status, i, nchunks_added = uc_pool->nchunks_added;
      unsigned long c_addr, uc_addr;

      if (mutex_lock_interruptible(&uc_pool->add_chunk_mutex) != 0)
            return -1;  /* interrupted by a signal */

      if (uc_pool->nchunks_added > nchunks_added) {
            /* someone added a new chunk while we were waiting */
            mutex_unlock(&uc_pool->add_chunk_mutex);
            return 0;
      }

      if (uc_pool->nchunks_added >= MAX_CONVERTED_CHUNKS_PER_NODE) {
            mutex_unlock(&uc_pool->add_chunk_mutex);
            return -1;
      }

      /* attempt to allocate a granule's worth of cached memory pages */

      page = alloc_pages_node(nid, GFP_KERNEL | __GFP_ZERO | GFP_THISNODE,
                        IA64_GRANULE_SHIFT-PAGE_SHIFT);
      if (!page) {
            mutex_unlock(&uc_pool->add_chunk_mutex);
            return -1;
      }

      /* convert the memory pages from cached to uncached */

      c_addr = (unsigned long)page_address(page);
      uc_addr = c_addr - PAGE_OFFSET + __IA64_UNCACHED_OFFSET;

      /*
       * There's a small race here where it's possible for someone to
       * access the page through /dev/mem halfway through the conversion
       * to uncached - not sure it's really worth bothering about
       */
      for (i = 0; i < (IA64_GRANULE_SIZE / PAGE_SIZE); i++)
            SetPageUncached(&page[i]);

      flush_tlb_kernel_range(uc_addr, uc_addr + IA64_GRANULE_SIZE);

      status = ia64_pal_prefetch_visibility(PAL_VISIBILITY_PHYSICAL);
      if (status == PAL_VISIBILITY_OK_REMOTE_NEEDED) {
            atomic_set(&uc_pool->status, 0);
            status = smp_call_function(uncached_ipi_visibility, uc_pool, 1);
            if (status || atomic_read(&uc_pool->status))
                  goto failed;
      } else if (status != PAL_VISIBILITY_OK)
            goto failed;

      preempt_disable();

      if (ia64_platform_is("sn2"))
            sn_flush_all_caches(uc_addr, IA64_GRANULE_SIZE);
      else
            flush_icache_range(uc_addr, uc_addr + IA64_GRANULE_SIZE);

      /* flush the just introduced uncached translation from the TLB */
      local_flush_tlb_all();

      preempt_enable();

      status = ia64_pal_mc_drain();
      if (status != PAL_STATUS_SUCCESS)
            goto failed;
      atomic_set(&uc_pool->status, 0);
      status = smp_call_function(uncached_ipi_mc_drain, uc_pool, 1);
      if (status || atomic_read(&uc_pool->status))
            goto failed;

      /*
       * The chunk of memory pages has been converted to uncached so now we
       * can add it to the pool.
       */
      status = gen_pool_add(uc_pool->pool, uc_addr, IA64_GRANULE_SIZE, nid);
      if (status)
            goto failed;

      uc_pool->nchunks_added++;
      mutex_unlock(&uc_pool->add_chunk_mutex);
      return 0;

      /* failed to convert or add the chunk so give it back to the kernel */
failed:
      for (i = 0; i < (IA64_GRANULE_SIZE / PAGE_SIZE); i++)
            ClearPageUncached(&page[i]);

      free_pages(c_addr, IA64_GRANULE_SHIFT-PAGE_SHIFT);
      mutex_unlock(&uc_pool->add_chunk_mutex);
      return -1;
}


/*
 * uncached_alloc_page
 *
 * @starting_nid: node id of node to start with, or -1
 * @n_pages: number of contiguous pages to allocate
 *
 * Allocate the specified number of contiguous uncached pages on the
 * the requested node. If not enough contiguous uncached pages are available
 * on the requested node, roundrobin starting with the next higher node.
 */
unsigned long uncached_alloc_page(int starting_nid, int n_pages)
{
      unsigned long uc_addr;
      struct uncached_pool *uc_pool;
      int nid;

      if (unlikely(starting_nid >= MAX_NUMNODES))
            return 0;

      if (starting_nid < 0)
            starting_nid = numa_node_id();
      nid = starting_nid;

      do {
            if (!node_state(nid, N_HIGH_MEMORY))
                  continue;
            uc_pool = &uncached_pools[nid];
            if (uc_pool->pool == NULL)
                  continue;
            do {
                  uc_addr = gen_pool_alloc(uc_pool->pool,
                                     n_pages * PAGE_SIZE);
                  if (uc_addr != 0)
                        return uc_addr;
            } while (uncached_add_chunk(uc_pool, nid) == 0);

      } while ((nid = (nid + 1) % MAX_NUMNODES) != starting_nid);

      return 0;
}
EXPORT_SYMBOL(uncached_alloc_page);


/*
 * uncached_free_page
 *
 * @uc_addr: uncached address of first page to free
 * @n_pages: number of contiguous pages to free
 *
 * Free the specified number of uncached pages.
 */
void uncached_free_page(unsigned long uc_addr, int n_pages)
{
      int nid = paddr_to_nid(uc_addr - __IA64_UNCACHED_OFFSET);
      struct gen_pool *pool = uncached_pools[nid].pool;

      if (unlikely(pool == NULL))
            return;

      if ((uc_addr & (0XFUL << 60)) != __IA64_UNCACHED_OFFSET)
            panic("uncached_free_page invalid address %lx\n", uc_addr);

      gen_pool_free(pool, uc_addr, n_pages * PAGE_SIZE);
}
EXPORT_SYMBOL(uncached_free_page);


/*
 * uncached_build_memmap,
 *
 * @uc_start: uncached starting address of a chunk of uncached memory
 * @uc_end: uncached ending address of a chunk of uncached memory
 * @arg: ignored, (NULL argument passed in on call to efi_memmap_walk_uc())
 *
 * Called at boot time to build a map of pages that can be used for
 * memory special operations.
 */
static int __init uncached_build_memmap(unsigned long uc_start,
                              unsigned long uc_end, void *arg)
{
      int nid = paddr_to_nid(uc_start - __IA64_UNCACHED_OFFSET);
      struct gen_pool *pool = uncached_pools[nid].pool;
      size_t size = uc_end - uc_start;

      touch_softlockup_watchdog();

      if (pool != NULL) {
            memset((char *)uc_start, 0, size);
            (void) gen_pool_add(pool, uc_start, size, nid);
      }
      return 0;
}


static int __init uncached_init(void)
{
      int nid;

      for_each_node_state(nid, N_ONLINE) {
            uncached_pools[nid].pool = gen_pool_create(PAGE_SHIFT, nid);
            mutex_init(&uncached_pools[nid].add_chunk_mutex);
      }

      efi_memmap_walk_uc(uncached_build_memmap, NULL);
      return 0;
}

__initcall(uncached_init);

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