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