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mspec.c

/*
 * 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/system.h>
#include <asm/pgtable.h>
#include <asm/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);
            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_nopfn
 *
 * Creates a mspec page and maps it to user space.
 */
static unsigned long
mspec_nopfn(struct vm_area_struct *vma, unsigned long address)
{
      unsigned long paddr, maddr;
      unsigned long pfn;
      int index;
      struct vma_data *vdata = vma->vm_private_data;

      BUG_ON(address < vdata->vm_start || address >= vdata->vm_end);
      index = (address - vdata->vm_start) >> PAGE_SHIFT;
      maddr = (volatile unsigned long) vdata->maddr[index];
      if (maddr == 0) {
            maddr = uncached_alloc_page(numa_node_id());
            if (maddr == 0)
                  return NOPFN_OOM;

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

      return pfn;
}

static struct vm_operations_struct mspec_vm_ops = {
      .open = mspec_open,
      .close = mspec_close,
      .nopfn = mspec_nopfn
};

/*
 * mspec_mmap
 *
 * Called when mmaping 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 = kmalloc(vdata_size, GFP_KERNEL);
      else {
            vdata = vmalloc(vdata_size);
            flags = VMD_VMALLOCED;
      }
      if (!vdata)
            return -ENOMEM;
      memset(vdata, 0, vdata_size);

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

      vma->vm_flags |= (VM_IO | VM_RESERVED | VM_PFNMAP | VM_DONTEXPAND);
      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
};

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
};

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
};

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);
                        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]);
      }
      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]);
            }
      }
}

module_init(mspec_init);
module_exit(mspec_exit);

MODULE_AUTHOR("Silicon Graphics, Inc. <linux-altix@sgi.com>");
MODULE_DESCRIPTION("Driver for SGI SN special memory operations");
MODULE_LICENSE("GPL");

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