1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Copyright (C) 2001-2006 Silicon Graphics, Inc. All rights
4 * reserved.
5 */
6
7 /*
8 * SN Platform Special Memory (mspec) Support
9 *
10 * This driver exports the SN special memory (mspec) facility to user
11 * processes.
12 * There are two types of memory made available thru this driver:
13 * uncached and cached.
14 *
15 * Uncached are used for memory write combining feature of the ia64
16 * cpu.
17 *
18 * Cached are used for areas of memory that are used as cached addresses
19 * on our partition and used as uncached addresses from other partitions.
20 * Due to a design constraint of the SN2 Shub, you can not have processors
21 * on the same FSB perform both a cached and uncached reference to the
22 * same cache line. These special memory cached regions prevent the
23 * kernel from ever dropping in a TLB entry and therefore prevent the
24 * processor from ever speculating a cache line from this page.
25 */
26
27 #include <linux/types.h>
28 #include <linux/kernel.h>
29 #include <linux/module.h>
30 #include <linux/init.h>
31 #include <linux/errno.h>
32 #include <linux/miscdevice.h>
33 #include <linux/spinlock.h>
34 #include <linux/mm.h>
35 #include <linux/fs.h>
36 #include <linux/vmalloc.h>
37 #include <linux/string.h>
38 #include <linux/slab.h>
39 #include <linux/numa.h>
40 #include <linux/refcount.h>
41 #include <asm/page.h>
42 #include <asm/pgtable.h>
43 #include <linux/atomic.h>
44 #include <asm/tlbflush.h>
45 #include <asm/uncached.h>
46
47
48 #define CACHED_ID "Cached,"
49 #define UNCACHED_ID "Uncached"
50 #define REVISION "4.0"
51 #define MSPEC_BASENAME "mspec"
52
53 /*
54 * Page types allocated by the device.
55 */
56 enum mspec_page_type {
57 MSPEC_CACHED = 2,
58 MSPEC_UNCACHED
59 };
60
61 /*
62 * One of these structures is allocated when an mspec region is mmaped. The
63 * structure is pointed to by the vma->vm_private_data field in the vma struct.
64 * This structure is used to record the addresses of the mspec pages.
65 * This structure is shared by all vma's that are split off from the
66 * original vma when split_vma()'s are done.
67 *
68 * The refcnt is incremented atomically because mm->mmap_sem does not
69 * protect in fork case where multiple tasks share the vma_data.
70 */
71 struct vma_data {
72 refcount_t refcnt; /* Number of vmas sharing the data. */
73 spinlock_t lock; /* Serialize access to this structure. */
74 int count; /* Number of pages allocated. */
75 enum mspec_page_type type; /* Type of pages allocated. */
76 unsigned long vm_start; /* Original (unsplit) base. */
77 unsigned long vm_end; /* Original (unsplit) end. */
78 unsigned long maddr[0]; /* Array of MSPEC addresses. */
79 };
80
81 /*
82 * mspec_open
83 *
84 * Called when a device mapping is created by a means other than mmap
85 * (via fork, munmap, etc.). Increments the reference count on the
86 * underlying mspec data so it is not freed prematurely.
87 */
88 static void
mspec_open(struct vm_area_struct * vma)89 mspec_open(struct vm_area_struct *vma)
90 {
91 struct vma_data *vdata;
92
93 vdata = vma->vm_private_data;
94 refcount_inc(&vdata->refcnt);
95 }
96
97 /*
98 * mspec_close
99 *
100 * Called when unmapping a device mapping. Frees all mspec pages
101 * belonging to all the vma's sharing this vma_data structure.
102 */
103 static void
mspec_close(struct vm_area_struct * vma)104 mspec_close(struct vm_area_struct *vma)
105 {
106 struct vma_data *vdata;
107 int index, last_index;
108 unsigned long my_page;
109
110 vdata = vma->vm_private_data;
111
112 if (!refcount_dec_and_test(&vdata->refcnt))
113 return;
114
115 last_index = (vdata->vm_end - vdata->vm_start) >> PAGE_SHIFT;
116 for (index = 0; index < last_index; index++) {
117 if (vdata->maddr[index] == 0)
118 continue;
119 /*
120 * Clear the page before sticking it back
121 * into the pool.
122 */
123 my_page = vdata->maddr[index];
124 vdata->maddr[index] = 0;
125 memset((char *)my_page, 0, PAGE_SIZE);
126 uncached_free_page(my_page, 1);
127 }
128
129 kvfree(vdata);
130 }
131
132 /*
133 * mspec_fault
134 *
135 * Creates a mspec page and maps it to user space.
136 */
137 static vm_fault_t
mspec_fault(struct vm_fault * vmf)138 mspec_fault(struct vm_fault *vmf)
139 {
140 unsigned long paddr, maddr;
141 unsigned long pfn;
142 pgoff_t index = vmf->pgoff;
143 struct vma_data *vdata = vmf->vma->vm_private_data;
144
145 maddr = (volatile unsigned long) vdata->maddr[index];
146 if (maddr == 0) {
147 maddr = uncached_alloc_page(numa_node_id(), 1);
148 if (maddr == 0)
149 return VM_FAULT_OOM;
150
151 spin_lock(&vdata->lock);
152 if (vdata->maddr[index] == 0) {
153 vdata->count++;
154 vdata->maddr[index] = maddr;
155 } else {
156 uncached_free_page(maddr, 1);
157 maddr = vdata->maddr[index];
158 }
159 spin_unlock(&vdata->lock);
160 }
161
162 paddr = maddr & ~__IA64_UNCACHED_OFFSET;
163 pfn = paddr >> PAGE_SHIFT;
164
165 return vmf_insert_pfn(vmf->vma, vmf->address, pfn);
166 }
167
168 static const struct vm_operations_struct mspec_vm_ops = {
169 .open = mspec_open,
170 .close = mspec_close,
171 .fault = mspec_fault,
172 };
173
174 /*
175 * mspec_mmap
176 *
177 * Called when mmapping the device. Initializes the vma with a fault handler
178 * and private data structure necessary to allocate, track, and free the
179 * underlying pages.
180 */
181 static int
mspec_mmap(struct file * file,struct vm_area_struct * vma,enum mspec_page_type type)182 mspec_mmap(struct file *file, struct vm_area_struct *vma,
183 enum mspec_page_type type)
184 {
185 struct vma_data *vdata;
186 int pages, vdata_size;
187
188 if (vma->vm_pgoff != 0)
189 return -EINVAL;
190
191 if ((vma->vm_flags & VM_SHARED) == 0)
192 return -EINVAL;
193
194 if ((vma->vm_flags & VM_WRITE) == 0)
195 return -EPERM;
196
197 pages = vma_pages(vma);
198 vdata_size = sizeof(struct vma_data) + pages * sizeof(long);
199 if (vdata_size <= PAGE_SIZE)
200 vdata = kzalloc(vdata_size, GFP_KERNEL);
201 else
202 vdata = vzalloc(vdata_size);
203 if (!vdata)
204 return -ENOMEM;
205
206 vdata->vm_start = vma->vm_start;
207 vdata->vm_end = vma->vm_end;
208 vdata->type = type;
209 spin_lock_init(&vdata->lock);
210 refcount_set(&vdata->refcnt, 1);
211 vma->vm_private_data = vdata;
212
213 vma->vm_flags |= VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP;
214 if (vdata->type == MSPEC_UNCACHED)
215 vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
216 vma->vm_ops = &mspec_vm_ops;
217
218 return 0;
219 }
220
221 static int
cached_mmap(struct file * file,struct vm_area_struct * vma)222 cached_mmap(struct file *file, struct vm_area_struct *vma)
223 {
224 return mspec_mmap(file, vma, MSPEC_CACHED);
225 }
226
227 static int
uncached_mmap(struct file * file,struct vm_area_struct * vma)228 uncached_mmap(struct file *file, struct vm_area_struct *vma)
229 {
230 return mspec_mmap(file, vma, MSPEC_UNCACHED);
231 }
232
233 static const struct file_operations cached_fops = {
234 .owner = THIS_MODULE,
235 .mmap = cached_mmap,
236 .llseek = noop_llseek,
237 };
238
239 static struct miscdevice cached_miscdev = {
240 .minor = MISC_DYNAMIC_MINOR,
241 .name = "mspec_cached",
242 .fops = &cached_fops
243 };
244
245 static const struct file_operations uncached_fops = {
246 .owner = THIS_MODULE,
247 .mmap = uncached_mmap,
248 .llseek = noop_llseek,
249 };
250
251 static struct miscdevice uncached_miscdev = {
252 .minor = MISC_DYNAMIC_MINOR,
253 .name = "mspec_uncached",
254 .fops = &uncached_fops
255 };
256
257 /*
258 * mspec_init
259 *
260 * Called at boot time to initialize the mspec facility.
261 */
262 static int __init
mspec_init(void)263 mspec_init(void)
264 {
265 int ret;
266
267 ret = misc_register(&cached_miscdev);
268 if (ret) {
269 printk(KERN_ERR "%s: failed to register device %i\n",
270 CACHED_ID, ret);
271 return ret;
272 }
273 ret = misc_register(&uncached_miscdev);
274 if (ret) {
275 printk(KERN_ERR "%s: failed to register device %i\n",
276 UNCACHED_ID, ret);
277 misc_deregister(&cached_miscdev);
278 return ret;
279 }
280
281 printk(KERN_INFO "%s %s initialized devices: %s %s\n",
282 MSPEC_BASENAME, REVISION, CACHED_ID, UNCACHED_ID);
283
284 return 0;
285 }
286
287 static void __exit
mspec_exit(void)288 mspec_exit(void)
289 {
290 misc_deregister(&uncached_miscdev);
291 misc_deregister(&cached_miscdev);
292 }
293
294 module_init(mspec_init);
295 module_exit(mspec_exit);
296
297 MODULE_AUTHOR("Silicon Graphics, Inc. <linux-altix@sgi.com>");
298 MODULE_DESCRIPTION("Driver for SGI SN special memory operations");
299 MODULE_LICENSE("GPL");
300