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TOMOYO Linux Cross Reference
Linux/virt/kvm/arm/arch_timer.c

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  1 /*
  2  * Copyright (C) 2012 ARM Ltd.
  3  * Author: Marc Zyngier <marc.zyngier@arm.com>
  4  *
  5  * This program is free software; you can redistribute it and/or modify
  6  * it under the terms of the GNU General Public License version 2 as
  7  * published by the Free Software Foundation.
  8  *
  9  * This program is distributed in the hope that it will be useful,
 10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
 11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 12  * GNU General Public License for more details.
 13  *
 14  * You should have received a copy of the GNU General Public License
 15  * along with this program; if not, write to the Free Software
 16  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 17  */
 18 
 19 #include <linux/cpu.h>
 20 #include <linux/kvm.h>
 21 #include <linux/kvm_host.h>
 22 #include <linux/interrupt.h>
 23 #include <linux/irq.h>
 24 
 25 #include <clocksource/arm_arch_timer.h>
 26 #include <asm/arch_timer.h>
 27 #include <asm/kvm_hyp.h>
 28 
 29 #include <kvm/arm_vgic.h>
 30 #include <kvm/arm_arch_timer.h>
 31 
 32 #include "trace.h"
 33 
 34 static struct timecounter *timecounter;
 35 static unsigned int host_vtimer_irq;
 36 static u32 host_vtimer_irq_flags;
 37 
 38 void kvm_timer_vcpu_put(struct kvm_vcpu *vcpu)
 39 {
 40         vcpu_vtimer(vcpu)->active_cleared_last = false;
 41 }
 42 
 43 u64 kvm_phys_timer_read(void)
 44 {
 45         return timecounter->cc->read(timecounter->cc);
 46 }
 47 
 48 static bool timer_is_armed(struct arch_timer_cpu *timer)
 49 {
 50         return timer->armed;
 51 }
 52 
 53 /* timer_arm: as in "arm the timer", not as in ARM the company */
 54 static void timer_arm(struct arch_timer_cpu *timer, u64 ns)
 55 {
 56         timer->armed = true;
 57         hrtimer_start(&timer->timer, ktime_add_ns(ktime_get(), ns),
 58                       HRTIMER_MODE_ABS);
 59 }
 60 
 61 static void timer_disarm(struct arch_timer_cpu *timer)
 62 {
 63         if (timer_is_armed(timer)) {
 64                 hrtimer_cancel(&timer->timer);
 65                 cancel_work_sync(&timer->expired);
 66                 timer->armed = false;
 67         }
 68 }
 69 
 70 static irqreturn_t kvm_arch_timer_handler(int irq, void *dev_id)
 71 {
 72         struct kvm_vcpu *vcpu = *(struct kvm_vcpu **)dev_id;
 73 
 74         /*
 75          * We disable the timer in the world switch and let it be
 76          * handled by kvm_timer_sync_hwstate(). Getting a timer
 77          * interrupt at this point is a sure sign of some major
 78          * breakage.
 79          */
 80         pr_warn("Unexpected interrupt %d on vcpu %p\n", irq, vcpu);
 81         return IRQ_HANDLED;
 82 }
 83 
 84 /*
 85  * Work function for handling the backup timer that we schedule when a vcpu is
 86  * no longer running, but had a timer programmed to fire in the future.
 87  */
 88 static void kvm_timer_inject_irq_work(struct work_struct *work)
 89 {
 90         struct kvm_vcpu *vcpu;
 91 
 92         vcpu = container_of(work, struct kvm_vcpu, arch.timer_cpu.expired);
 93 
 94         /*
 95          * If the vcpu is blocked we want to wake it up so that it will see
 96          * the timer has expired when entering the guest.
 97          */
 98         kvm_vcpu_kick(vcpu);
 99 }
100 
101 static u64 kvm_timer_compute_delta(struct arch_timer_context *timer_ctx)
102 {
103         u64 cval, now;
104 
105         cval = timer_ctx->cnt_cval;
106         now = kvm_phys_timer_read() - timer_ctx->cntvoff;
107 
108         if (now < cval) {
109                 u64 ns;
110 
111                 ns = cyclecounter_cyc2ns(timecounter->cc,
112                                          cval - now,
113                                          timecounter->mask,
114                                          &timecounter->frac);
115                 return ns;
116         }
117 
118         return 0;
119 }
120 
121 static bool kvm_timer_irq_can_fire(struct arch_timer_context *timer_ctx)
122 {
123         return !(timer_ctx->cnt_ctl & ARCH_TIMER_CTRL_IT_MASK) &&
124                 (timer_ctx->cnt_ctl & ARCH_TIMER_CTRL_ENABLE);
125 }
126 
127 /*
128  * Returns the earliest expiration time in ns among guest timers.
129  * Note that it will return 0 if none of timers can fire.
130  */
131 static u64 kvm_timer_earliest_exp(struct kvm_vcpu *vcpu)
132 {
133         u64 min_virt = ULLONG_MAX, min_phys = ULLONG_MAX;
134         struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
135         struct arch_timer_context *ptimer = vcpu_ptimer(vcpu);
136 
137         if (kvm_timer_irq_can_fire(vtimer))
138                 min_virt = kvm_timer_compute_delta(vtimer);
139 
140         if (kvm_timer_irq_can_fire(ptimer))
141                 min_phys = kvm_timer_compute_delta(ptimer);
142 
143         /* If none of timers can fire, then return 0 */
144         if ((min_virt == ULLONG_MAX) && (min_phys == ULLONG_MAX))
145                 return 0;
146 
147         return min(min_virt, min_phys);
148 }
149 
150 static enum hrtimer_restart kvm_timer_expire(struct hrtimer *hrt)
151 {
152         struct arch_timer_cpu *timer;
153         struct kvm_vcpu *vcpu;
154         u64 ns;
155 
156         timer = container_of(hrt, struct arch_timer_cpu, timer);
157         vcpu = container_of(timer, struct kvm_vcpu, arch.timer_cpu);
158 
159         /*
160          * Check that the timer has really expired from the guest's
161          * PoV (NTP on the host may have forced it to expire
162          * early). If we should have slept longer, restart it.
163          */
164         ns = kvm_timer_earliest_exp(vcpu);
165         if (unlikely(ns)) {
166                 hrtimer_forward_now(hrt, ns_to_ktime(ns));
167                 return HRTIMER_RESTART;
168         }
169 
170         schedule_work(&timer->expired);
171         return HRTIMER_NORESTART;
172 }
173 
174 bool kvm_timer_should_fire(struct arch_timer_context *timer_ctx)
175 {
176         u64 cval, now;
177 
178         if (!kvm_timer_irq_can_fire(timer_ctx))
179                 return false;
180 
181         cval = timer_ctx->cnt_cval;
182         now = kvm_phys_timer_read() - timer_ctx->cntvoff;
183 
184         return cval <= now;
185 }
186 
187 static void kvm_timer_update_irq(struct kvm_vcpu *vcpu, bool new_level,
188                                  struct arch_timer_context *timer_ctx)
189 {
190         int ret;
191 
192         BUG_ON(!vgic_initialized(vcpu->kvm));
193 
194         timer_ctx->active_cleared_last = false;
195         timer_ctx->irq.level = new_level;
196         trace_kvm_timer_update_irq(vcpu->vcpu_id, timer_ctx->irq.irq,
197                                    timer_ctx->irq.level);
198 
199         ret = kvm_vgic_inject_irq(vcpu->kvm, vcpu->vcpu_id, timer_ctx->irq.irq,
200                                   timer_ctx->irq.level);
201         WARN_ON(ret);
202 }
203 
204 /*
205  * Check if there was a change in the timer state (should we raise or lower
206  * the line level to the GIC).
207  */
208 static int kvm_timer_update_state(struct kvm_vcpu *vcpu)
209 {
210         struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
211         struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
212         struct arch_timer_context *ptimer = vcpu_ptimer(vcpu);
213 
214         /*
215          * If userspace modified the timer registers via SET_ONE_REG before
216          * the vgic was initialized, we mustn't set the vtimer->irq.level value
217          * because the guest would never see the interrupt.  Instead wait
218          * until we call this function from kvm_timer_flush_hwstate.
219          */
220         if (!vgic_initialized(vcpu->kvm) || !timer->enabled)
221                 return -ENODEV;
222 
223         if (kvm_timer_should_fire(vtimer) != vtimer->irq.level)
224                 kvm_timer_update_irq(vcpu, !vtimer->irq.level, vtimer);
225 
226         if (kvm_timer_should_fire(ptimer) != ptimer->irq.level)
227                 kvm_timer_update_irq(vcpu, !ptimer->irq.level, ptimer);
228 
229         return 0;
230 }
231 
232 /* Schedule the background timer for the emulated timer. */
233 static void kvm_timer_emulate(struct kvm_vcpu *vcpu,
234                               struct arch_timer_context *timer_ctx)
235 {
236         struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
237 
238         if (kvm_timer_should_fire(timer_ctx))
239                 return;
240 
241         if (!kvm_timer_irq_can_fire(timer_ctx))
242                 return;
243 
244         /*  The timer has not yet expired, schedule a background timer */
245         timer_arm(timer, kvm_timer_compute_delta(timer_ctx));
246 }
247 
248 /*
249  * Schedule the background timer before calling kvm_vcpu_block, so that this
250  * thread is removed from its waitqueue and made runnable when there's a timer
251  * interrupt to handle.
252  */
253 void kvm_timer_schedule(struct kvm_vcpu *vcpu)
254 {
255         struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
256         struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
257         struct arch_timer_context *ptimer = vcpu_ptimer(vcpu);
258 
259         BUG_ON(timer_is_armed(timer));
260 
261         /*
262          * No need to schedule a background timer if any guest timer has
263          * already expired, because kvm_vcpu_block will return before putting
264          * the thread to sleep.
265          */
266         if (kvm_timer_should_fire(vtimer) || kvm_timer_should_fire(ptimer))
267                 return;
268 
269         /*
270          * If both timers are not capable of raising interrupts (disabled or
271          * masked), then there's no more work for us to do.
272          */
273         if (!kvm_timer_irq_can_fire(vtimer) && !kvm_timer_irq_can_fire(ptimer))
274                 return;
275 
276         /*
277          * The guest timers have not yet expired, schedule a background timer.
278          * Set the earliest expiration time among the guest timers.
279          */
280         timer_arm(timer, kvm_timer_earliest_exp(vcpu));
281 }
282 
283 void kvm_timer_unschedule(struct kvm_vcpu *vcpu)
284 {
285         struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
286         timer_disarm(timer);
287 }
288 
289 /**
290  * kvm_timer_flush_hwstate - prepare to move the virt timer to the cpu
291  * @vcpu: The vcpu pointer
292  *
293  * Check if the virtual timer has expired while we were running in the host,
294  * and inject an interrupt if that was the case.
295  */
296 void kvm_timer_flush_hwstate(struct kvm_vcpu *vcpu)
297 {
298         struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
299         bool phys_active;
300         int ret;
301 
302         if (kvm_timer_update_state(vcpu))
303                 return;
304 
305         /* Set the background timer for the physical timer emulation. */
306         kvm_timer_emulate(vcpu, vcpu_ptimer(vcpu));
307 
308         /*
309         * If we enter the guest with the virtual input level to the VGIC
310         * asserted, then we have already told the VGIC what we need to, and
311         * we don't need to exit from the guest until the guest deactivates
312         * the already injected interrupt, so therefore we should set the
313         * hardware active state to prevent unnecessary exits from the guest.
314         *
315         * Also, if we enter the guest with the virtual timer interrupt active,
316         * then it must be active on the physical distributor, because we set
317         * the HW bit and the guest must be able to deactivate the virtual and
318         * physical interrupt at the same time.
319         *
320         * Conversely, if the virtual input level is deasserted and the virtual
321         * interrupt is not active, then always clear the hardware active state
322         * to ensure that hardware interrupts from the timer triggers a guest
323         * exit.
324         */
325         phys_active = vtimer->irq.level ||
326                         kvm_vgic_map_is_active(vcpu, vtimer->irq.irq);
327 
328         /*
329          * We want to avoid hitting the (re)distributor as much as
330          * possible, as this is a potentially expensive MMIO access
331          * (not to mention locks in the irq layer), and a solution for
332          * this is to cache the "active" state in memory.
333          *
334          * Things to consider: we cannot cache an "active set" state,
335          * because the HW can change this behind our back (it becomes
336          * "clear" in the HW). We must then restrict the caching to
337          * the "clear" state.
338          *
339          * The cache is invalidated on:
340          * - vcpu put, indicating that the HW cannot be trusted to be
341          *   in a sane state on the next vcpu load,
342          * - any change in the interrupt state
343          *
344          * Usage conditions:
345          * - cached value is "active clear"
346          * - value to be programmed is "active clear"
347          */
348         if (vtimer->active_cleared_last && !phys_active)
349                 return;
350 
351         ret = irq_set_irqchip_state(host_vtimer_irq,
352                                     IRQCHIP_STATE_ACTIVE,
353                                     phys_active);
354         WARN_ON(ret);
355 
356         vtimer->active_cleared_last = !phys_active;
357 }
358 
359 /**
360  * kvm_timer_sync_hwstate - sync timer state from cpu
361  * @vcpu: The vcpu pointer
362  *
363  * Check if the virtual timer has expired while we were running in the guest,
364  * and inject an interrupt if that was the case.
365  */
366 void kvm_timer_sync_hwstate(struct kvm_vcpu *vcpu)
367 {
368         struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
369 
370         /*
371          * This is to cancel the background timer for the physical timer
372          * emulation if it is set.
373          */
374         timer_disarm(timer);
375 
376         /*
377          * The guest could have modified the timer registers or the timer
378          * could have expired, update the timer state.
379          */
380         kvm_timer_update_state(vcpu);
381 }
382 
383 int kvm_timer_vcpu_reset(struct kvm_vcpu *vcpu,
384                          const struct kvm_irq_level *virt_irq,
385                          const struct kvm_irq_level *phys_irq)
386 {
387         struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
388         struct arch_timer_context *ptimer = vcpu_ptimer(vcpu);
389 
390         /*
391          * The vcpu timer irq number cannot be determined in
392          * kvm_timer_vcpu_init() because it is called much before
393          * kvm_vcpu_set_target(). To handle this, we determine
394          * vcpu timer irq number when the vcpu is reset.
395          */
396         vtimer->irq.irq = virt_irq->irq;
397         ptimer->irq.irq = phys_irq->irq;
398 
399         /*
400          * The bits in CNTV_CTL are architecturally reset to UNKNOWN for ARMv8
401          * and to 0 for ARMv7.  We provide an implementation that always
402          * resets the timer to be disabled and unmasked and is compliant with
403          * the ARMv7 architecture.
404          */
405         vtimer->cnt_ctl = 0;
406         ptimer->cnt_ctl = 0;
407         kvm_timer_update_state(vcpu);
408 
409         return 0;
410 }
411 
412 /* Make the updates of cntvoff for all vtimer contexts atomic */
413 static void update_vtimer_cntvoff(struct kvm_vcpu *vcpu, u64 cntvoff)
414 {
415         int i;
416         struct kvm *kvm = vcpu->kvm;
417         struct kvm_vcpu *tmp;
418 
419         mutex_lock(&kvm->lock);
420         kvm_for_each_vcpu(i, tmp, kvm)
421                 vcpu_vtimer(tmp)->cntvoff = cntvoff;
422 
423         /*
424          * When called from the vcpu create path, the CPU being created is not
425          * included in the loop above, so we just set it here as well.
426          */
427         vcpu_vtimer(vcpu)->cntvoff = cntvoff;
428         mutex_unlock(&kvm->lock);
429 }
430 
431 void kvm_timer_vcpu_init(struct kvm_vcpu *vcpu)
432 {
433         struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
434 
435         /* Synchronize cntvoff across all vtimers of a VM. */
436         update_vtimer_cntvoff(vcpu, kvm_phys_timer_read());
437         vcpu_ptimer(vcpu)->cntvoff = 0;
438 
439         INIT_WORK(&timer->expired, kvm_timer_inject_irq_work);
440         hrtimer_init(&timer->timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
441         timer->timer.function = kvm_timer_expire;
442 }
443 
444 static void kvm_timer_init_interrupt(void *info)
445 {
446         enable_percpu_irq(host_vtimer_irq, host_vtimer_irq_flags);
447 }
448 
449 int kvm_arm_timer_set_reg(struct kvm_vcpu *vcpu, u64 regid, u64 value)
450 {
451         struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
452 
453         switch (regid) {
454         case KVM_REG_ARM_TIMER_CTL:
455                 vtimer->cnt_ctl = value;
456                 break;
457         case KVM_REG_ARM_TIMER_CNT:
458                 update_vtimer_cntvoff(vcpu, kvm_phys_timer_read() - value);
459                 break;
460         case KVM_REG_ARM_TIMER_CVAL:
461                 vtimer->cnt_cval = value;
462                 break;
463         default:
464                 return -1;
465         }
466 
467         kvm_timer_update_state(vcpu);
468         return 0;
469 }
470 
471 u64 kvm_arm_timer_get_reg(struct kvm_vcpu *vcpu, u64 regid)
472 {
473         struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
474 
475         switch (regid) {
476         case KVM_REG_ARM_TIMER_CTL:
477                 return vtimer->cnt_ctl;
478         case KVM_REG_ARM_TIMER_CNT:
479                 return kvm_phys_timer_read() - vtimer->cntvoff;
480         case KVM_REG_ARM_TIMER_CVAL:
481                 return vtimer->cnt_cval;
482         }
483         return (u64)-1;
484 }
485 
486 static int kvm_timer_starting_cpu(unsigned int cpu)
487 {
488         kvm_timer_init_interrupt(NULL);
489         return 0;
490 }
491 
492 static int kvm_timer_dying_cpu(unsigned int cpu)
493 {
494         disable_percpu_irq(host_vtimer_irq);
495         return 0;
496 }
497 
498 int kvm_timer_hyp_init(void)
499 {
500         struct arch_timer_kvm_info *info;
501         int err;
502 
503         info = arch_timer_get_kvm_info();
504         timecounter = &info->timecounter;
505 
506         if (!timecounter->cc) {
507                 kvm_err("kvm_arch_timer: uninitialized timecounter\n");
508                 return -ENODEV;
509         }
510 
511         if (info->virtual_irq <= 0) {
512                 kvm_err("kvm_arch_timer: invalid virtual timer IRQ: %d\n",
513                         info->virtual_irq);
514                 return -ENODEV;
515         }
516         host_vtimer_irq = info->virtual_irq;
517 
518         host_vtimer_irq_flags = irq_get_trigger_type(host_vtimer_irq);
519         if (host_vtimer_irq_flags != IRQF_TRIGGER_HIGH &&
520             host_vtimer_irq_flags != IRQF_TRIGGER_LOW) {
521                 kvm_err("Invalid trigger for IRQ%d, assuming level low\n",
522                         host_vtimer_irq);
523                 host_vtimer_irq_flags = IRQF_TRIGGER_LOW;
524         }
525 
526         err = request_percpu_irq(host_vtimer_irq, kvm_arch_timer_handler,
527                                  "kvm guest timer", kvm_get_running_vcpus());
528         if (err) {
529                 kvm_err("kvm_arch_timer: can't request interrupt %d (%d)\n",
530                         host_vtimer_irq, err);
531                 return err;
532         }
533 
534         kvm_info("virtual timer IRQ%d\n", host_vtimer_irq);
535 
536         cpuhp_setup_state(CPUHP_AP_KVM_ARM_TIMER_STARTING,
537                           "kvm/arm/timer:starting", kvm_timer_starting_cpu,
538                           kvm_timer_dying_cpu);
539         return err;
540 }
541 
542 void kvm_timer_vcpu_terminate(struct kvm_vcpu *vcpu)
543 {
544         struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
545         struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
546 
547         timer_disarm(timer);
548         kvm_vgic_unmap_phys_irq(vcpu, vtimer->irq.irq);
549 }
550 
551 int kvm_timer_enable(struct kvm_vcpu *vcpu)
552 {
553         struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
554         struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
555         struct irq_desc *desc;
556         struct irq_data *data;
557         int phys_irq;
558         int ret;
559 
560         if (timer->enabled)
561                 return 0;
562 
563         /*
564          * Find the physical IRQ number corresponding to the host_vtimer_irq
565          */
566         desc = irq_to_desc(host_vtimer_irq);
567         if (!desc) {
568                 kvm_err("%s: no interrupt descriptor\n", __func__);
569                 return -EINVAL;
570         }
571 
572         data = irq_desc_get_irq_data(desc);
573         while (data->parent_data)
574                 data = data->parent_data;
575 
576         phys_irq = data->hwirq;
577 
578         /*
579          * Tell the VGIC that the virtual interrupt is tied to a
580          * physical interrupt. We do that once per VCPU.
581          */
582         ret = kvm_vgic_map_phys_irq(vcpu, vtimer->irq.irq, phys_irq);
583         if (ret)
584                 return ret;
585 
586         timer->enabled = 1;
587 
588         return 0;
589 }
590 
591 /*
592  * On VHE system, we only need to configure trap on physical timer and counter
593  * accesses in EL0 and EL1 once, not for every world switch.
594  * The host kernel runs at EL2 with HCR_EL2.TGE == 1,
595  * and this makes those bits have no effect for the host kernel execution.
596  */
597 void kvm_timer_init_vhe(void)
598 {
599         /* When HCR_EL2.E2H ==1, EL1PCEN and EL1PCTEN are shifted by 10 */
600         u32 cnthctl_shift = 10;
601         u64 val;
602 
603         /*
604          * Disallow physical timer access for the guest.
605          * Physical counter access is allowed.
606          */
607         val = read_sysreg(cnthctl_el2);
608         val &= ~(CNTHCTL_EL1PCEN << cnthctl_shift);
609         val |= (CNTHCTL_EL1PCTEN << cnthctl_shift);
610         write_sysreg(val, cnthctl_el2);
611 }
612 

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