1 /*
2  * SN Platform GRU Driver
3  *
4  * 		MMUOPS callbacks  + TLB flushing
5  *
6  * This file handles emu notifier callbacks from the core kernel. The callbacks
7  * are used to update the TLB in the GRU as a result of changes in the
8  * state of a process address space. This file also handles TLB invalidates
9  * from the GRU driver.
10  *
11  *  Copyright (c) 2008 Silicon Graphics, Inc.  All Rights Reserved.
12  *
13  *  This program is free software; you can redistribute it and/or modify
14  *  it under the terms of the GNU General Public License as published by
15  *  the Free Software Foundation; either version 2 of the License, or
16  *  (at your option) any later version.
17  *
18  *  This program is distributed in the hope that it will be useful,
19  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
20  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
21  *  GNU General Public License for more details.
22  *
23  *  You should have received a copy of the GNU General Public License
24  *  along with this program; if not, write to the Free Software
25  *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
26  */
27 
28 #include <linux/kernel.h>
29 #include <linux/list.h>
30 #include <linux/spinlock.h>
31 #include <linux/mm.h>
32 #include <linux/slab.h>
33 #include <linux/device.h>
34 #include <linux/hugetlb.h>
35 #include <linux/delay.h>
36 #include <linux/timex.h>
37 #include <linux/srcu.h>
38 #include <asm/processor.h>
39 #include "gru.h"
40 #include "grutables.h"
41 #include <asm/uv/uv_hub.h>
42 
43 #define gru_random()	get_cycles()
44 
45 /* ---------------------------------- TLB Invalidation functions --------
46  * get_tgh_handle
47  *
48  * Find a TGH to use for issuing a TLB invalidate. For GRUs that are on the
49  * local blade, use a fixed TGH that is a function of the blade-local cpu
50  * number. Normally, this TGH is private to the cpu & no contention occurs for
51  * the TGH. For offblade GRUs, select a random TGH in the range above the
52  * private TGHs. A spinlock is required to access this TGH & the lock must be
53  * released when the invalidate is completes. This sucks, but it is the best we
54  * can do.
55  *
56  * Note that the spinlock is IN the TGH handle so locking does not involve
57  * additional cache lines.
58  *
59  */
60 static inline int get_off_blade_tgh(struct gru_state *gru)
61 {
62 	int n;
63 
64 	n = GRU_NUM_TGH - gru->gs_tgh_first_remote;
65 	n = gru_random() % n;
66 	n += gru->gs_tgh_first_remote;
67 	return n;
68 }
69 
70 static inline int get_on_blade_tgh(struct gru_state *gru)
71 {
72 	return uv_blade_processor_id() >> gru->gs_tgh_local_shift;
73 }
74 
75 static struct gru_tlb_global_handle *get_lock_tgh_handle(struct gru_state
76 							 *gru)
77 {
78 	struct gru_tlb_global_handle *tgh;
79 	int n;
80 
81 	preempt_disable();
82 	if (uv_numa_blade_id() == gru->gs_blade_id)
83 		n = get_on_blade_tgh(gru);
84 	else
85 		n = get_off_blade_tgh(gru);
86 	tgh = get_tgh_by_index(gru, n);
87 	lock_tgh_handle(tgh);
88 
89 	return tgh;
90 }
91 
92 static void get_unlock_tgh_handle(struct gru_tlb_global_handle *tgh)
93 {
94 	unlock_tgh_handle(tgh);
95 	preempt_enable();
96 }
97 
98 /*
99  * gru_flush_tlb_range
100  *
101  * General purpose TLB invalidation function. This function scans every GRU in
102  * the ENTIRE system (partition) looking for GRUs where the specified MM has
103  * been accessed by the GRU. For each GRU found, the TLB must be invalidated OR
104  * the ASID invalidated. Invalidating an ASID causes a new ASID to be assigned
105  * on the next fault. This effectively flushes the ENTIRE TLB for the MM at the
106  * cost of (possibly) a large number of future TLBmisses.
107  *
108  * The current algorithm is optimized based on the following (somewhat true)
109  * assumptions:
110  * 	- GRU contexts are not loaded into a GRU unless a reference is made to
111  * 	  the data segment or control block (this is true, not an assumption).
112  * 	  If a DS/CB is referenced, the user will also issue instructions that
113  * 	  cause TLBmisses. It is not necessary to optimize for the case where
114  * 	  contexts are loaded but no instructions cause TLB misses. (I know
115  * 	  this will happen but I'm not optimizing for it).
116  * 	- GRU instructions to invalidate TLB entries are SLOOOOWWW - normally
117  * 	  a few usec but in unusual cases, it could be longer. Avoid if
118  * 	  possible.
119  * 	- intrablade process migration between cpus is not frequent but is
120  * 	  common.
121  * 	- a GRU context is not typically migrated to a different GRU on the
122  * 	  blade because of intrablade migration
123  *	- interblade migration is rare. Processes migrate their GRU context to
124  *	  the new blade.
125  *	- if interblade migration occurs, migration back to the original blade
126  *	  is very very rare (ie., no optimization for this case)
127  *	- most GRU instruction operate on a subset of the user REGIONS. Code
128  *	  & shared library regions are not likely targets of GRU instructions.
129  *
130  * To help improve the efficiency of TLB invalidation, the GMS data
131  * structure is maintained for EACH address space (MM struct). The GMS is
132  * also the structure that contains the pointer to the mmu callout
133  * functions. This structure is linked to the mm_struct for the address space
134  * using the mmu "register" function. The mmu interfaces are used to
135  * provide the callbacks for TLB invalidation. The GMS contains:
136  *
137  * 	- asid[maxgrus] array. ASIDs are assigned to a GRU when a context is
138  * 	  loaded into the GRU.
139  * 	- asidmap[maxgrus]. bitmap to make it easier to find non-zero asids in
140  * 	  the above array
141  *	- ctxbitmap[maxgrus]. Indicates the contexts that are currently active
142  *	  in the GRU for the address space. This bitmap must be passed to the
143  *	  GRU to do an invalidate.
144  *
145  * The current algorithm for invalidating TLBs is:
146  * 	- scan the asidmap for GRUs where the context has been loaded, ie,
147  * 	  asid is non-zero.
148  * 	- for each gru found:
149  * 		- if the ctxtmap is non-zero, there are active contexts in the
150  * 		  GRU. TLB invalidate instructions must be issued to the GRU.
151  *		- if the ctxtmap is zero, no context is active. Set the ASID to
152  *		  zero to force a full TLB invalidation. This is fast but will
153  *		  cause a lot of TLB misses if the context is reloaded onto the
154  *		  GRU
155  *
156  */
157 
158 void gru_flush_tlb_range(struct gru_mm_struct *gms, unsigned long start,
159 			 unsigned long len)
160 {
161 	struct gru_state *gru;
162 	struct gru_mm_tracker *asids;
163 	struct gru_tlb_global_handle *tgh;
164 	unsigned long num;
165 	int grupagesize, pagesize, pageshift, gid, asid;
166 
167 	/* ZZZ TODO - handle huge pages */
168 	pageshift = PAGE_SHIFT;
169 	pagesize = (1UL << pageshift);
170 	grupagesize = GRU_PAGESIZE(pageshift);
171 	num = min(((len + pagesize - 1) >> pageshift), GRUMAXINVAL);
172 
173 	STAT(flush_tlb);
174 	gru_dbg(grudev, "gms %p, start 0x%lx, len 0x%lx, asidmap 0x%lx\n", gms,
175 		start, len, gms->ms_asidmap[0]);
176 
177 	spin_lock(&gms->ms_asid_lock);
178 	for_each_gru_in_bitmap(gid, gms->ms_asidmap) {
179 		STAT(flush_tlb_gru);
180 		gru = GID_TO_GRU(gid);
181 		asids = gms->ms_asids + gid;
182 		asid = asids->mt_asid;
183 		if (asids->mt_ctxbitmap && asid) {
184 			STAT(flush_tlb_gru_tgh);
185 			asid = GRUASID(asid, start);
186 			gru_dbg(grudev,
187 	"  FLUSH gruid %d, asid 0x%x, vaddr 0x%lx, vamask 0x%x, num %ld, cbmap 0x%x\n",
188 			      gid, asid, start, grupagesize, num, asids->mt_ctxbitmap);
189 			tgh = get_lock_tgh_handle(gru);
190 			tgh_invalidate(tgh, start, ~0, asid, grupagesize, 0,
191 				       num - 1, asids->mt_ctxbitmap);
192 			get_unlock_tgh_handle(tgh);
193 		} else {
194 			STAT(flush_tlb_gru_zero_asid);
195 			asids->mt_asid = 0;
196 			__clear_bit(gru->gs_gid, gms->ms_asidmap);
197 			gru_dbg(grudev,
198 	"  CLEARASID gruid %d, asid 0x%x, cbtmap 0x%x, asidmap 0x%lx\n",
199 				gid, asid, asids->mt_ctxbitmap,
200 				gms->ms_asidmap[0]);
201 		}
202 	}
203 	spin_unlock(&gms->ms_asid_lock);
204 }
205 
206 /*
207  * Flush the entire TLB on a chiplet.
208  */
209 void gru_flush_all_tlb(struct gru_state *gru)
210 {
211 	struct gru_tlb_global_handle *tgh;
212 
213 	gru_dbg(grudev, "gid %d\n", gru->gs_gid);
214 	tgh = get_lock_tgh_handle(gru);
215 	tgh_invalidate(tgh, 0, ~0, 0, 1, 1, GRUMAXINVAL - 1, 0xffff);
216 	get_unlock_tgh_handle(tgh);
217 }
218 
219 /*
220  * MMUOPS notifier callout functions
221  */
222 static int gru_invalidate_range_start(struct mmu_notifier *mn,
223 				       struct mm_struct *mm,
224 				       unsigned long start, unsigned long end,
225 				       bool blockable)
226 {
227 	struct gru_mm_struct *gms = container_of(mn, struct gru_mm_struct,
228 						 ms_notifier);
229 
230 	STAT(mmu_invalidate_range);
231 	atomic_inc(&gms->ms_range_active);
232 	gru_dbg(grudev, "gms %p, start 0x%lx, end 0x%lx, act %d\n", gms,
233 		start, end, atomic_read(&gms->ms_range_active));
234 	gru_flush_tlb_range(gms, start, end - start);
235 
236 	return 0;
237 }
238 
239 static void gru_invalidate_range_end(struct mmu_notifier *mn,
240 				     struct mm_struct *mm, unsigned long start,
241 				     unsigned long end)
242 {
243 	struct gru_mm_struct *gms = container_of(mn, struct gru_mm_struct,
244 						 ms_notifier);
245 
246 	/* ..._and_test() provides needed barrier */
247 	(void)atomic_dec_and_test(&gms->ms_range_active);
248 
249 	wake_up_all(&gms->ms_wait_queue);
250 	gru_dbg(grudev, "gms %p, start 0x%lx, end 0x%lx\n", gms, start, end);
251 }
252 
253 static void gru_release(struct mmu_notifier *mn, struct mm_struct *mm)
254 {
255 	struct gru_mm_struct *gms = container_of(mn, struct gru_mm_struct,
256 						 ms_notifier);
257 
258 	gms->ms_released = 1;
259 	gru_dbg(grudev, "gms %p\n", gms);
260 }
261 
262 
263 static const struct mmu_notifier_ops gru_mmuops = {
264 	.invalidate_range_start	= gru_invalidate_range_start,
265 	.invalidate_range_end	= gru_invalidate_range_end,
266 	.release		= gru_release,
267 };
268 
269 /* Move this to the basic mmu_notifier file. But for now... */
270 static struct mmu_notifier *mmu_find_ops(struct mm_struct *mm,
271 			const struct mmu_notifier_ops *ops)
272 {
273 	struct mmu_notifier *mn, *gru_mn = NULL;
274 
275 	if (mm->mmu_notifier_mm) {
276 		rcu_read_lock();
277 		hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list,
278 					 hlist)
279 		    if (mn->ops == ops) {
280 			gru_mn = mn;
281 			break;
282 		}
283 		rcu_read_unlock();
284 	}
285 	return gru_mn;
286 }
287 
288 struct gru_mm_struct *gru_register_mmu_notifier(void)
289 {
290 	struct gru_mm_struct *gms;
291 	struct mmu_notifier *mn;
292 	int err;
293 
294 	mn = mmu_find_ops(current->mm, &gru_mmuops);
295 	if (mn) {
296 		gms = container_of(mn, struct gru_mm_struct, ms_notifier);
297 		atomic_inc(&gms->ms_refcnt);
298 	} else {
299 		gms = kzalloc(sizeof(*gms), GFP_KERNEL);
300 		if (!gms)
301 			return ERR_PTR(-ENOMEM);
302 		STAT(gms_alloc);
303 		spin_lock_init(&gms->ms_asid_lock);
304 		gms->ms_notifier.ops = &gru_mmuops;
305 		atomic_set(&gms->ms_refcnt, 1);
306 		init_waitqueue_head(&gms->ms_wait_queue);
307 		err = __mmu_notifier_register(&gms->ms_notifier, current->mm);
308 		if (err)
309 			goto error;
310 	}
311 	if (gms)
312 		gru_dbg(grudev, "gms %p, refcnt %d\n", gms,
313 			atomic_read(&gms->ms_refcnt));
314 	return gms;
315 error:
316 	kfree(gms);
317 	return ERR_PTR(err);
318 }
319 
320 void gru_drop_mmu_notifier(struct gru_mm_struct *gms)
321 {
322 	gru_dbg(grudev, "gms %p, refcnt %d, released %d\n", gms,
323 		atomic_read(&gms->ms_refcnt), gms->ms_released);
324 	if (atomic_dec_return(&gms->ms_refcnt) == 0) {
325 		if (!gms->ms_released)
326 			mmu_notifier_unregister(&gms->ms_notifier, current->mm);
327 		kfree(gms);
328 		STAT(gms_free);
329 	}
330 }
331 
332 /*
333  * Setup TGH parameters. There are:
334  * 	- 24 TGH handles per GRU chiplet
335  * 	- a portion (MAX_LOCAL_TGH) of the handles are reserved for
336  * 	  use by blade-local cpus
337  * 	- the rest are used by off-blade cpus. This usage is
338  * 	  less frequent than blade-local usage.
339  *
340  * For now, use 16 handles for local flushes, 8 for remote flushes. If the blade
341  * has less tan or equal to 16 cpus, each cpu has a unique handle that it can
342  * use.
343  */
344 #define MAX_LOCAL_TGH	16
345 
346 void gru_tgh_flush_init(struct gru_state *gru)
347 {
348 	int cpus, shift = 0, n;
349 
350 	cpus = uv_blade_nr_possible_cpus(gru->gs_blade_id);
351 
352 	/* n = cpus rounded up to next power of 2 */
353 	if (cpus) {
354 		n = 1 << fls(cpus - 1);
355 
356 		/*
357 		 * shift count for converting local cpu# to TGH index
358 		 *      0 if cpus <= MAX_LOCAL_TGH,
359 		 *      1 if cpus <= 2*MAX_LOCAL_TGH,
360 		 *      etc
361 		 */
362 		shift = max(0, fls(n - 1) - fls(MAX_LOCAL_TGH - 1));
363 	}
364 	gru->gs_tgh_local_shift = shift;
365 
366 	/* first starting TGH index to use for remote purges */
367 	gru->gs_tgh_first_remote = (cpus + (1 << shift) - 1) >> shift;
368 
369 }
370