uncached.c

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/*
 * 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/efi.h>
#include <linux/genalloc.h>
#include <linux/gfp.h>
#include <asm/page.h>
#include <asm/pal.h>
#include <asm/pgtable.h>
#include <linux/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_exact_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(u64 uc_start, u64 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);