[PATCH] mspec driver

Implement the special memory driver (mspec) based on the do_no_pfn
approach.  The driver is currently used only on SN2 hardware with special
fetchop support but could be beneficial on other architectures using the
uncached mode.

Signed-off-by: Jes Sorensen <jes@sgi.com>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 421 insertions, 0 deletions

diff --git a/drivers/char/mspec.c b/drivers/char/mspec.c
new file mode 100644
index 000000000000..5426b1e5595f
--- /dev/null
+++ b/drivers/char/mspec.c
@@ -0,0 +1,421 @@
+/*
+ * 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/config.h>
+#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/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_FETCHOP = 1,
+        MSPEC_CACHED,
+        MSPEC_UNCACHED
+};
+
+static int is_sn2;
+
+/*
+ * 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.
+ */
+struct vma_data {
+        atomic_t refcnt;        /* Number of vmas sharing the data. */
+        spinlock_t lock;        /* Serialize access to the vma. */
+        int count;              /* Number of pages allocated. */
+        int type;               /* Type of pages allocated. */
+        unsigned long maddr[0]; /* Array of MSPEC addresses. */
+};
+
+/* 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, 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 the vma.
+ */
+static void
+mspec_close(struct vm_area_struct *vma)
+{
+        struct vma_data *vdata;
+        int i, pages, result, vdata_size;
+
+        vdata = vma->vm_private_data;
+        if (!atomic_dec_and_test(&vdata->refcnt))
+                return;
+
+        pages = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
+        vdata_size = sizeof(struct vma_data) + pages * sizeof(long);
+        for (i = 0; i < pages; i++) {
+                if (vdata->maddr[i] == 0)
+                        continue;
+                /*
+                 * Clear the page before sticking it back
+                 * into the pool.
+                 */
+                result = mspec_zero_block(vdata->maddr[i], PAGE_SIZE);
+                if (!result)
+                        uncached_free_page(vdata->maddr[i]);
+                else
+                        printk(KERN_WARNING "mspec_close(): "
+                               "failed to zero page %i\n",
+                               result);
+        }
+
+        if (vdata_size <= PAGE_SIZE)
+                kfree(vdata);
+        else
+                vfree(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;
+
+        index = (address - vma->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 = __pa(TO_CAC(maddr));
+
+        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, int type)
+{
+        struct vma_data *vdata;
+        int pages, vdata_size;
+
+        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);
+        if (!vdata)
+                return -ENOMEM;
+        memset(vdata, 0, vdata_size);
+
+        vdata->type = type;
+        spin_lock_init(&vdata->lock);
+        vdata->refcnt = ATOMIC_INIT(1);
+        vma->vm_private_data = vdata;
+
+        vma->vm_flags |= (VM_IO | VM_LOCKED | VM_RESERVED | VM_PFNMAP);
+        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 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 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 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
+         */
+        if (ia64_platform_is("sn2")) {
+                is_sn2 = 1;
+                if (is_shub2()) {
+                        ret = -ENOMEM;
+                        for_each_online_node(nid) {
+                                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;
+                }
+        }
+        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");