mspec.c

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/*
 * Copyright (C) 2001-2006 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.
 */

/*
 * SN Platform Special Memory (mspec) Support
 *
 * This driver exports the SN special memory (mspec) facility to user
 * processes.
 * There are three types of memory made available thru this driver:
 * fetchops, uncached and cached.
 *
 * Fetchops are atomic memory operations that are implemented in the
 * memory controller on SGI SN hardware.
 *
 * Uncached are used for memory write combining feature of the ia64
 * cpu.
 *
 * Cached are used for areas of memory that are used as cached addresses
 * on our partition and used as uncached addresses from other partitions.
 * Due to a design constraint of the SN2 Shub, you can not have processors
 * on the same FSB perform both a cached and uncached reference to the
 * same cache line.  These special memory cached regions prevent the
 * kernel from ever dropping in a TLB entry and therefore prevent the
 * processor from ever speculating a cache line from this page.
 */

#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/errno.h>
#include <linux/miscdevice.h>
#include <linux/spinlock.h>
#include <linux/mm.h>
#include <linux/fs.h>
#include <linux/vmalloc.h>
#include <linux/string.h>
#include <linux/slab.h>
#include <linux/numa.h>
#include <asm/page.h>
#include <asm/pgtable.h>
#include <linux/atomic.h>
#include <asm/tlbflush.h>
#include <asm/uncached.h>
#include <asm/sn/addrs.h>
#include <asm/sn/arch.h>
#include <asm/sn/mspec.h>
#include <asm/sn/sn_cpuid.h>
#include <asm/sn/io.h>
#include <asm/sn/bte.h>
#include <asm/sn/shubio.h>


#define FETCHOP_ID  "SGI Fetchop,"
#define CACHED_ID   "Cached,"
#define UNCACHED_ID "Uncached"
#define REVISION    "4.0"
#define MSPEC_BASENAME  "mspec"

/*
 * Page types allocated by the device.
 */
enum mspec_page_type {
    MSPEC_FETCHOP = 1,
    MSPEC_CACHED,
    MSPEC_UNCACHED
};

#ifdef CONFIG_SGI_SN
static int is_sn2;
#else
#define is_sn2      0
#endif

/*
 * One of these structures is allocated when an mspec region is mmaped. The
 * structure is pointed to by the vma->vm_private_data field in the vma struct.
 * This structure is used to record the addresses of the mspec pages.
 * This structure is shared by all vma's that are split off from the
 * original vma when split_vma()'s are done.
 *
 * The refcnt is incremented atomically because mm->mmap_sem does not
 * protect in fork case where multiple tasks share the vma_data.
 */
struct vma_data {
    atomic_t refcnt;    /* Number of vmas sharing the data. */
    spinlock_t lock;    /* Serialize access to this structure. */
    int count;      /* Number of pages allocated. */
    enum mspec_page_type type; /* Type of pages allocated. */
    int flags;      /* See VMD_xxx below. */
    unsigned long vm_start; /* Original (unsplit) base. */
    unsigned long vm_end;   /* Original (unsplit) end. */
    unsigned long maddr[0]; /* Array of MSPEC addresses. */
};

#define VMD_VMALLOCED 0x1   /* vmalloc'd rather than kmalloc'd */

/* used on shub2 to clear FOP cache in the HUB */
static unsigned long scratch_page[MAX_NUMNODES];
#define SH2_AMO_CACHE_ENTRIES   4

static inline int
mspec_zero_block(unsigned long addr, int len)
{
    int status;

    if (is_sn2) {
        if (is_shub2()) {
            int nid;
            void *p;
            int i;

            nid = nasid_to_cnodeid(get_node_number(__pa(addr)));
            p = (void *)TO_AMO(scratch_page[nid]);

            for (i=0; i < SH2_AMO_CACHE_ENTRIES; i++) {
                FETCHOP_LOAD_OP(p, FETCHOP_LOAD);
                p += FETCHOP_VAR_SIZE;
            }
        }

        status = bte_copy(0, addr & ~__IA64_UNCACHED_OFFSET, len,
                  BTE_WACQUIRE | BTE_ZERO_FILL, NULL);
    } else {
        memset((char *) addr, 0, len);
        status = 0;
    }
    return status;
}

/*
 * mspec_open
 *
 * Called when a device mapping is created by a means other than mmap
 * (via fork, munmap, etc.).  Increments the reference count on the
 * underlying mspec data so it is not freed prematurely.
 */
static void
mspec_open(struct vm_area_struct *vma)
{
    struct vma_data *vdata;

    vdata = vma->vm_private_data;
    atomic_inc(&vdata->refcnt);
}

/*
 * mspec_close
 *
 * Called when unmapping a device mapping. Frees all mspec pages
 * belonging to all the vma's sharing this vma_data structure.
 */
static void
mspec_close(struct vm_area_struct *vma)
{
    struct vma_data *vdata;
    int index, last_index;
    unsigned long my_page;

    vdata = vma->vm_private_data;

    if (!atomic_dec_and_test(&vdata->refcnt))
        return;

    last_index = (vdata->vm_end - vdata->vm_start) >> PAGE_SHIFT;
    for (index = 0; index < last_index; index++) {
        if (vdata->maddr[index] == 0)
            continue;
        /*
         * Clear the page before sticking it back
         * into the pool.
         */
        my_page = vdata->maddr[index];
        vdata->maddr[index] = 0;
        if (!mspec_zero_block(my_page, PAGE_SIZE))
            uncached_free_page(my_page, 1);
        else
            printk(KERN_WARNING "mspec_close(): "
                   "failed to zero page %ld\n", my_page);
    }

    if (vdata->flags & VMD_VMALLOCED)
        vfree(vdata);
    else
        kfree(vdata);
}

/*
 * mspec_fault
 *
 * Creates a mspec page and maps it to user space.
 */
static int
mspec_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
{
    unsigned long paddr, maddr;
    unsigned long pfn;
    pgoff_t index = vmf->pgoff;
    struct vma_data *vdata = vma->vm_private_data;

    maddr = (volatile unsigned long) vdata->maddr[index];
    if (maddr == 0) {
        maddr = uncached_alloc_page(numa_node_id(), 1);
        if (maddr == 0)
            return VM_FAULT_OOM;

        spin_lock(&vdata->lock);
        if (vdata->maddr[index] == 0) {
            vdata->count++;
            vdata->maddr[index] = maddr;
        } else {
            uncached_free_page(maddr, 1);
            maddr = vdata->maddr[index];
        }
        spin_unlock(&vdata->lock);
    }

    if (vdata->type == MSPEC_FETCHOP)
        paddr = TO_AMO(maddr);
    else
        paddr = maddr & ~__IA64_UNCACHED_OFFSET;

    pfn = paddr >> PAGE_SHIFT;

    /*
     * vm_insert_pfn can fail with -EBUSY, but in that case it will
     * be because another thread has installed the pte first, so it
     * is no problem.
     */
    vm_insert_pfn(vma, (unsigned long)vmf->virtual_address, pfn);

    return VM_FAULT_NOPAGE;
}

static const struct vm_operations_struct mspec_vm_ops = {
    .open = mspec_open,
    .close = mspec_close,
    .fault = mspec_fault,
};

/*
 * mspec_mmap
 *
 * Called when mmapping the device.  Initializes the vma with a fault handler
 * and private data structure necessary to allocate, track, and free the
 * underlying pages.
 */
static int
mspec_mmap(struct file *file, struct vm_area_struct *vma,
                    enum mspec_page_type type)
{
    struct vma_data *vdata;
    int pages, vdata_size, flags = 0;

    if (vma->vm_pgoff != 0)
        return -EINVAL;

    if ((vma->vm_flags & VM_SHARED) == 0)
        return -EINVAL;

    if ((vma->vm_flags & VM_WRITE) == 0)
        return -EPERM;

    pages = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
    vdata_size = sizeof(struct vma_data) + pages * sizeof(long);
    if (vdata_size <= PAGE_SIZE)
        vdata = kzalloc(vdata_size, GFP_KERNEL);
    else {
        vdata = vzalloc(vdata_size);
        flags = VMD_VMALLOCED;
    }
    if (!vdata)
        return -ENOMEM;

    vdata->vm_start = vma->vm_start;
    vdata->vm_end = vma->vm_end;
    vdata->flags = flags;
    vdata->type = type;
    spin_lock_init(&vdata->lock);
    atomic_set(&vdata->refcnt, 1);
    vma->vm_private_data = vdata;

    vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP;
    if (vdata->type == MSPEC_FETCHOP || vdata->type == MSPEC_UNCACHED)
        vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
    vma->vm_ops = &mspec_vm_ops;

    return 0;
}

static int
fetchop_mmap(struct file *file, struct vm_area_struct *vma)
{
    return mspec_mmap(file, vma, MSPEC_FETCHOP);
}

static int
cached_mmap(struct file *file, struct vm_area_struct *vma)
{
    return mspec_mmap(file, vma, MSPEC_CACHED);
}

static int
uncached_mmap(struct file *file, struct vm_area_struct *vma)
{
    return mspec_mmap(file, vma, MSPEC_UNCACHED);
}

static const struct file_operations fetchop_fops = {
    .owner = THIS_MODULE,
    .mmap = fetchop_mmap,
    .llseek = noop_llseek,
};

static struct miscdevice fetchop_miscdev = {
    .minor = MISC_DYNAMIC_MINOR,
    .name = "sgi_fetchop",
    .fops = &fetchop_fops
};

static const struct file_operations cached_fops = {
    .owner = THIS_MODULE,
    .mmap = cached_mmap,
    .llseek = noop_llseek,
};

static struct miscdevice cached_miscdev = {
    .minor = MISC_DYNAMIC_MINOR,
    .name = "mspec_cached",
    .fops = &cached_fops
};

static const struct file_operations uncached_fops = {
    .owner = THIS_MODULE,
    .mmap = uncached_mmap,
    .llseek = noop_llseek,
};

static struct miscdevice uncached_miscdev = {
    .minor = MISC_DYNAMIC_MINOR,
    .name = "mspec_uncached",
    .fops = &uncached_fops
};

/*
 * mspec_init
 *
 * Called at boot time to initialize the mspec facility.
 */
static int __init
mspec_init(void)
{
    int ret;
    int nid;

    /*
     * The fetchop device only works on SN2 hardware, uncached and cached
     * memory drivers should both be valid on all ia64 hardware
     */
#ifdef CONFIG_SGI_SN
    if (ia64_platform_is("sn2")) {
        is_sn2 = 1;
        if (is_shub2()) {
            ret = -ENOMEM;
            for_each_node_state(nid, N_ONLINE) {
                int actual_nid;
                int nasid;
                unsigned long phys;

                scratch_page[nid] = uncached_alloc_page(nid, 1);
                if (scratch_page[nid] == 0)
                    goto free_scratch_pages;
                phys = __pa(scratch_page[nid]);
                nasid = get_node_number(phys);
                actual_nid = nasid_to_cnodeid(nasid);
                if (actual_nid != nid)
                    goto free_scratch_pages;
            }
        }

        ret = misc_register(&fetchop_miscdev);
        if (ret) {
            printk(KERN_ERR
                   "%s: failed to register device %i\n",
                   FETCHOP_ID, ret);
            goto free_scratch_pages;
        }
    }
#endif
    ret = misc_register(&cached_miscdev);
    if (ret) {
        printk(KERN_ERR "%s: failed to register device %i\n",
               CACHED_ID, ret);
        if (is_sn2)
            misc_deregister(&fetchop_miscdev);
        goto free_scratch_pages;
    }
    ret = misc_register(&uncached_miscdev);
    if (ret) {
        printk(KERN_ERR "%s: failed to register device %i\n",
               UNCACHED_ID, ret);
        misc_deregister(&cached_miscdev);
        if (is_sn2)
            misc_deregister(&fetchop_miscdev);
        goto free_scratch_pages;
    }

    printk(KERN_INFO "%s %s initialized devices: %s %s %s\n",
           MSPEC_BASENAME, REVISION, is_sn2 ? FETCHOP_ID : "",
           CACHED_ID, UNCACHED_ID);

    return 0;

 free_scratch_pages:
    for_each_node(nid) {
        if (scratch_page[nid] != 0)
            uncached_free_page(scratch_page[nid], 1);
    }
    return ret;
}

static void __exit
mspec_exit(void)
{
    int nid;

    misc_deregister(&uncached_miscdev);
    misc_deregister(&cached_miscdev);
    if (is_sn2) {
        misc_deregister(&fetchop_miscdev);

        for_each_node(nid) {
            if (scratch_page[nid] != 0)
                uncached_free_page(scratch_page[nid], 1);
        }
    }
}

module_init(mspec_init);
module_exit(mspec_exit);

MODULE_AUTHOR("Silicon Graphics, Inc. <[email protected]>");
MODULE_DESCRIPTION("Driver for SGI SN special memory operations");
MODULE_LICENSE("GPL");