xref: /openbmc/linux/arch/s390/kernel/vtime.c (revision 517a2390)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  *    Virtual cpu timer based timer functions.
4  *
5  *    Copyright IBM Corp. 2004, 2012
6  *    Author(s): Jan Glauber <jan.glauber@de.ibm.com>
7  */
8 
9 #include <linux/kernel_stat.h>
10 #include <linux/export.h>
11 #include <linux/kernel.h>
12 #include <linux/timex.h>
13 #include <linux/types.h>
14 #include <linux/time.h>
15 #include <asm/alternative.h>
16 #include <asm/cputime.h>
17 #include <asm/vtimer.h>
18 #include <asm/vtime.h>
19 #include <asm/cpu_mf.h>
20 #include <asm/smp.h>
21 
22 #include "entry.h"
23 
24 static void virt_timer_expire(void);
25 
26 static LIST_HEAD(virt_timer_list);
27 static DEFINE_SPINLOCK(virt_timer_lock);
28 static atomic64_t virt_timer_current;
29 static atomic64_t virt_timer_elapsed;
30 
31 DEFINE_PER_CPU(u64, mt_cycles[8]);
32 static DEFINE_PER_CPU(u64, mt_scaling_mult) = { 1 };
33 static DEFINE_PER_CPU(u64, mt_scaling_div) = { 1 };
34 static DEFINE_PER_CPU(u64, mt_scaling_jiffies);
35 
get_vtimer(void)36 static inline u64 get_vtimer(void)
37 {
38 	u64 timer;
39 
40 	asm volatile("stpt %0" : "=Q" (timer));
41 	return timer;
42 }
43 
set_vtimer(u64 expires)44 static inline void set_vtimer(u64 expires)
45 {
46 	u64 timer;
47 
48 	asm volatile(
49 		"	stpt	%0\n"	/* Store current cpu timer value */
50 		"	spt	%1"	/* Set new value imm. afterwards */
51 		: "=Q" (timer) : "Q" (expires));
52 	S390_lowcore.system_timer += S390_lowcore.last_update_timer - timer;
53 	S390_lowcore.last_update_timer = expires;
54 }
55 
virt_timer_forward(u64 elapsed)56 static inline int virt_timer_forward(u64 elapsed)
57 {
58 	BUG_ON(!irqs_disabled());
59 
60 	if (list_empty(&virt_timer_list))
61 		return 0;
62 	elapsed = atomic64_add_return(elapsed, &virt_timer_elapsed);
63 	return elapsed >= atomic64_read(&virt_timer_current);
64 }
65 
update_mt_scaling(void)66 static void update_mt_scaling(void)
67 {
68 	u64 cycles_new[8], *cycles_old;
69 	u64 delta, fac, mult, div;
70 	int i;
71 
72 	stcctm(MT_DIAG, smp_cpu_mtid + 1, cycles_new);
73 	cycles_old = this_cpu_ptr(mt_cycles);
74 	fac = 1;
75 	mult = div = 0;
76 	for (i = 0; i <= smp_cpu_mtid; i++) {
77 		delta = cycles_new[i] - cycles_old[i];
78 		div += delta;
79 		mult *= i + 1;
80 		mult += delta * fac;
81 		fac *= i + 1;
82 	}
83 	div *= fac;
84 	if (div > 0) {
85 		/* Update scaling factor */
86 		__this_cpu_write(mt_scaling_mult, mult);
87 		__this_cpu_write(mt_scaling_div, div);
88 		memcpy(cycles_old, cycles_new,
89 		       sizeof(u64) * (smp_cpu_mtid + 1));
90 	}
91 	__this_cpu_write(mt_scaling_jiffies, jiffies_64);
92 }
93 
update_tsk_timer(unsigned long * tsk_vtime,u64 new)94 static inline u64 update_tsk_timer(unsigned long *tsk_vtime, u64 new)
95 {
96 	u64 delta;
97 
98 	delta = new - *tsk_vtime;
99 	*tsk_vtime = new;
100 	return delta;
101 }
102 
103 
scale_vtime(u64 vtime)104 static inline u64 scale_vtime(u64 vtime)
105 {
106 	u64 mult = __this_cpu_read(mt_scaling_mult);
107 	u64 div = __this_cpu_read(mt_scaling_div);
108 
109 	if (smp_cpu_mtid)
110 		return vtime * mult / div;
111 	return vtime;
112 }
113 
account_system_index_scaled(struct task_struct * p,u64 cputime,enum cpu_usage_stat index)114 static void account_system_index_scaled(struct task_struct *p, u64 cputime,
115 					enum cpu_usage_stat index)
116 {
117 	p->stimescaled += cputime_to_nsecs(scale_vtime(cputime));
118 	account_system_index_time(p, cputime_to_nsecs(cputime), index);
119 }
120 
121 /*
122  * Update process times based on virtual cpu times stored by entry.S
123  * to the lowcore fields user_timer, system_timer & steal_clock.
124  */
do_account_vtime(struct task_struct * tsk)125 static int do_account_vtime(struct task_struct *tsk)
126 {
127 	u64 timer, clock, user, guest, system, hardirq, softirq;
128 
129 	timer = S390_lowcore.last_update_timer;
130 	clock = S390_lowcore.last_update_clock;
131 	asm volatile(
132 		"	stpt	%0\n"	/* Store current cpu timer value */
133 		"	stckf	%1"	/* Store current tod clock value */
134 		: "=Q" (S390_lowcore.last_update_timer),
135 		  "=Q" (S390_lowcore.last_update_clock)
136 		: : "cc");
137 	clock = S390_lowcore.last_update_clock - clock;
138 	timer -= S390_lowcore.last_update_timer;
139 
140 	if (hardirq_count())
141 		S390_lowcore.hardirq_timer += timer;
142 	else
143 		S390_lowcore.system_timer += timer;
144 
145 	/* Update MT utilization calculation */
146 	if (smp_cpu_mtid &&
147 	    time_after64(jiffies_64, this_cpu_read(mt_scaling_jiffies)))
148 		update_mt_scaling();
149 
150 	/* Calculate cputime delta */
151 	user = update_tsk_timer(&tsk->thread.user_timer,
152 				READ_ONCE(S390_lowcore.user_timer));
153 	guest = update_tsk_timer(&tsk->thread.guest_timer,
154 				 READ_ONCE(S390_lowcore.guest_timer));
155 	system = update_tsk_timer(&tsk->thread.system_timer,
156 				  READ_ONCE(S390_lowcore.system_timer));
157 	hardirq = update_tsk_timer(&tsk->thread.hardirq_timer,
158 				   READ_ONCE(S390_lowcore.hardirq_timer));
159 	softirq = update_tsk_timer(&tsk->thread.softirq_timer,
160 				   READ_ONCE(S390_lowcore.softirq_timer));
161 	S390_lowcore.steal_timer +=
162 		clock - user - guest - system - hardirq - softirq;
163 
164 	/* Push account value */
165 	if (user) {
166 		account_user_time(tsk, cputime_to_nsecs(user));
167 		tsk->utimescaled += cputime_to_nsecs(scale_vtime(user));
168 	}
169 
170 	if (guest) {
171 		account_guest_time(tsk, cputime_to_nsecs(guest));
172 		tsk->utimescaled += cputime_to_nsecs(scale_vtime(guest));
173 	}
174 
175 	if (system)
176 		account_system_index_scaled(tsk, system, CPUTIME_SYSTEM);
177 	if (hardirq)
178 		account_system_index_scaled(tsk, hardirq, CPUTIME_IRQ);
179 	if (softirq)
180 		account_system_index_scaled(tsk, softirq, CPUTIME_SOFTIRQ);
181 
182 	return virt_timer_forward(user + guest + system + hardirq + softirq);
183 }
184 
vtime_task_switch(struct task_struct * prev)185 void vtime_task_switch(struct task_struct *prev)
186 {
187 	do_account_vtime(prev);
188 	prev->thread.user_timer = S390_lowcore.user_timer;
189 	prev->thread.guest_timer = S390_lowcore.guest_timer;
190 	prev->thread.system_timer = S390_lowcore.system_timer;
191 	prev->thread.hardirq_timer = S390_lowcore.hardirq_timer;
192 	prev->thread.softirq_timer = S390_lowcore.softirq_timer;
193 	S390_lowcore.user_timer = current->thread.user_timer;
194 	S390_lowcore.guest_timer = current->thread.guest_timer;
195 	S390_lowcore.system_timer = current->thread.system_timer;
196 	S390_lowcore.hardirq_timer = current->thread.hardirq_timer;
197 	S390_lowcore.softirq_timer = current->thread.softirq_timer;
198 }
199 
200 /*
201  * In s390, accounting pending user time also implies
202  * accounting system time in order to correctly compute
203  * the stolen time accounting.
204  */
vtime_flush(struct task_struct * tsk)205 void vtime_flush(struct task_struct *tsk)
206 {
207 	u64 steal, avg_steal;
208 
209 	if (do_account_vtime(tsk))
210 		virt_timer_expire();
211 
212 	steal = S390_lowcore.steal_timer;
213 	avg_steal = S390_lowcore.avg_steal_timer;
214 	if ((s64) steal > 0) {
215 		S390_lowcore.steal_timer = 0;
216 		account_steal_time(cputime_to_nsecs(steal));
217 		avg_steal += steal;
218 	}
219 	S390_lowcore.avg_steal_timer = avg_steal / 2;
220 }
221 
vtime_delta(void)222 static u64 vtime_delta(void)
223 {
224 	u64 timer = S390_lowcore.last_update_timer;
225 
226 	S390_lowcore.last_update_timer = get_vtimer();
227 
228 	return timer - S390_lowcore.last_update_timer;
229 }
230 
231 /*
232  * Update process times based on virtual cpu times stored by entry.S
233  * to the lowcore fields user_timer, system_timer & steal_clock.
234  */
vtime_account_kernel(struct task_struct * tsk)235 void vtime_account_kernel(struct task_struct *tsk)
236 {
237 	u64 delta = vtime_delta();
238 
239 	if (tsk->flags & PF_VCPU)
240 		S390_lowcore.guest_timer += delta;
241 	else
242 		S390_lowcore.system_timer += delta;
243 
244 	virt_timer_forward(delta);
245 }
246 EXPORT_SYMBOL_GPL(vtime_account_kernel);
247 
vtime_account_softirq(struct task_struct * tsk)248 void vtime_account_softirq(struct task_struct *tsk)
249 {
250 	u64 delta = vtime_delta();
251 
252 	S390_lowcore.softirq_timer += delta;
253 
254 	virt_timer_forward(delta);
255 }
256 
vtime_account_hardirq(struct task_struct * tsk)257 void vtime_account_hardirq(struct task_struct *tsk)
258 {
259 	u64 delta = vtime_delta();
260 
261 	S390_lowcore.hardirq_timer += delta;
262 
263 	virt_timer_forward(delta);
264 }
265 
266 /*
267  * Sorted add to a list. List is linear searched until first bigger
268  * element is found.
269  */
list_add_sorted(struct vtimer_list * timer,struct list_head * head)270 static void list_add_sorted(struct vtimer_list *timer, struct list_head *head)
271 {
272 	struct vtimer_list *tmp;
273 
274 	list_for_each_entry(tmp, head, entry) {
275 		if (tmp->expires > timer->expires) {
276 			list_add_tail(&timer->entry, &tmp->entry);
277 			return;
278 		}
279 	}
280 	list_add_tail(&timer->entry, head);
281 }
282 
283 /*
284  * Handler for expired virtual CPU timer.
285  */
virt_timer_expire(void)286 static void virt_timer_expire(void)
287 {
288 	struct vtimer_list *timer, *tmp;
289 	unsigned long elapsed;
290 	LIST_HEAD(cb_list);
291 
292 	/* walk timer list, fire all expired timers */
293 	spin_lock(&virt_timer_lock);
294 	elapsed = atomic64_read(&virt_timer_elapsed);
295 	list_for_each_entry_safe(timer, tmp, &virt_timer_list, entry) {
296 		if (timer->expires < elapsed)
297 			/* move expired timer to the callback queue */
298 			list_move_tail(&timer->entry, &cb_list);
299 		else
300 			timer->expires -= elapsed;
301 	}
302 	if (!list_empty(&virt_timer_list)) {
303 		timer = list_first_entry(&virt_timer_list,
304 					 struct vtimer_list, entry);
305 		atomic64_set(&virt_timer_current, timer->expires);
306 	}
307 	atomic64_sub(elapsed, &virt_timer_elapsed);
308 	spin_unlock(&virt_timer_lock);
309 
310 	/* Do callbacks and recharge periodic timers */
311 	list_for_each_entry_safe(timer, tmp, &cb_list, entry) {
312 		list_del_init(&timer->entry);
313 		timer->function(timer->data);
314 		if (timer->interval) {
315 			/* Recharge interval timer */
316 			timer->expires = timer->interval +
317 				atomic64_read(&virt_timer_elapsed);
318 			spin_lock(&virt_timer_lock);
319 			list_add_sorted(timer, &virt_timer_list);
320 			spin_unlock(&virt_timer_lock);
321 		}
322 	}
323 }
324 
init_virt_timer(struct vtimer_list * timer)325 void init_virt_timer(struct vtimer_list *timer)
326 {
327 	timer->function = NULL;
328 	INIT_LIST_HEAD(&timer->entry);
329 }
330 EXPORT_SYMBOL(init_virt_timer);
331 
vtimer_pending(struct vtimer_list * timer)332 static inline int vtimer_pending(struct vtimer_list *timer)
333 {
334 	return !list_empty(&timer->entry);
335 }
336 
internal_add_vtimer(struct vtimer_list * timer)337 static void internal_add_vtimer(struct vtimer_list *timer)
338 {
339 	if (list_empty(&virt_timer_list)) {
340 		/* First timer, just program it. */
341 		atomic64_set(&virt_timer_current, timer->expires);
342 		atomic64_set(&virt_timer_elapsed, 0);
343 		list_add(&timer->entry, &virt_timer_list);
344 	} else {
345 		/* Update timer against current base. */
346 		timer->expires += atomic64_read(&virt_timer_elapsed);
347 		if (likely((s64) timer->expires <
348 			   (s64) atomic64_read(&virt_timer_current)))
349 			/* The new timer expires before the current timer. */
350 			atomic64_set(&virt_timer_current, timer->expires);
351 		/* Insert new timer into the list. */
352 		list_add_sorted(timer, &virt_timer_list);
353 	}
354 }
355 
__add_vtimer(struct vtimer_list * timer,int periodic)356 static void __add_vtimer(struct vtimer_list *timer, int periodic)
357 {
358 	unsigned long flags;
359 
360 	timer->interval = periodic ? timer->expires : 0;
361 	spin_lock_irqsave(&virt_timer_lock, flags);
362 	internal_add_vtimer(timer);
363 	spin_unlock_irqrestore(&virt_timer_lock, flags);
364 }
365 
366 /*
367  * add_virt_timer - add a oneshot virtual CPU timer
368  */
add_virt_timer(struct vtimer_list * timer)369 void add_virt_timer(struct vtimer_list *timer)
370 {
371 	__add_vtimer(timer, 0);
372 }
373 EXPORT_SYMBOL(add_virt_timer);
374 
375 /*
376  * add_virt_timer_int - add an interval virtual CPU timer
377  */
add_virt_timer_periodic(struct vtimer_list * timer)378 void add_virt_timer_periodic(struct vtimer_list *timer)
379 {
380 	__add_vtimer(timer, 1);
381 }
382 EXPORT_SYMBOL(add_virt_timer_periodic);
383 
__mod_vtimer(struct vtimer_list * timer,u64 expires,int periodic)384 static int __mod_vtimer(struct vtimer_list *timer, u64 expires, int periodic)
385 {
386 	unsigned long flags;
387 	int rc;
388 
389 	BUG_ON(!timer->function);
390 
391 	if (timer->expires == expires && vtimer_pending(timer))
392 		return 1;
393 	spin_lock_irqsave(&virt_timer_lock, flags);
394 	rc = vtimer_pending(timer);
395 	if (rc)
396 		list_del_init(&timer->entry);
397 	timer->interval = periodic ? expires : 0;
398 	timer->expires = expires;
399 	internal_add_vtimer(timer);
400 	spin_unlock_irqrestore(&virt_timer_lock, flags);
401 	return rc;
402 }
403 
404 /*
405  * returns whether it has modified a pending timer (1) or not (0)
406  */
mod_virt_timer(struct vtimer_list * timer,u64 expires)407 int mod_virt_timer(struct vtimer_list *timer, u64 expires)
408 {
409 	return __mod_vtimer(timer, expires, 0);
410 }
411 EXPORT_SYMBOL(mod_virt_timer);
412 
413 /*
414  * returns whether it has modified a pending timer (1) or not (0)
415  */
mod_virt_timer_periodic(struct vtimer_list * timer,u64 expires)416 int mod_virt_timer_periodic(struct vtimer_list *timer, u64 expires)
417 {
418 	return __mod_vtimer(timer, expires, 1);
419 }
420 EXPORT_SYMBOL(mod_virt_timer_periodic);
421 
422 /*
423  * Delete a virtual timer.
424  *
425  * returns whether the deleted timer was pending (1) or not (0)
426  */
del_virt_timer(struct vtimer_list * timer)427 int del_virt_timer(struct vtimer_list *timer)
428 {
429 	unsigned long flags;
430 
431 	if (!vtimer_pending(timer))
432 		return 0;
433 	spin_lock_irqsave(&virt_timer_lock, flags);
434 	list_del_init(&timer->entry);
435 	spin_unlock_irqrestore(&virt_timer_lock, flags);
436 	return 1;
437 }
438 EXPORT_SYMBOL(del_virt_timer);
439 
440 /*
441  * Start the virtual CPU timer on the current CPU.
442  */
vtime_init(void)443 void vtime_init(void)
444 {
445 	/* set initial cpu timer */
446 	set_vtimer(VTIMER_MAX_SLICE);
447 	/* Setup initial MT scaling values */
448 	if (smp_cpu_mtid) {
449 		__this_cpu_write(mt_scaling_jiffies, jiffies);
450 		__this_cpu_write(mt_scaling_mult, 1);
451 		__this_cpu_write(mt_scaling_div, 1);
452 		stcctm(MT_DIAG, smp_cpu_mtid + 1, this_cpu_ptr(mt_cycles));
453 	}
454 }
455