kernel/virt/kvm/arm/arch_timer.c

   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/of_irq.h>
  21 #include <linux/kvm.h>
  22 #include <linux/kvm_host.h>
  23 #include <linux/interrupt.h>
  24
  25 #include <clocksource/arm_arch_timer.h>
  26 #include <asm/arch_timer.h>
  27
  28 #include <kvm/arm_vgic.h>
  29 #include <kvm/arm_arch_timer.h>
  30
  31 #include "trace.h"
  32
  33 static struct timecounter *timecounter;
  34 static struct workqueue_struct *wqueue;
  35 static unsigned int host_vtimer_irq;
  36
  37 static cycle_t kvm_phys_timer_read(void)
  38 {
  39         return timecounter->cc->read(timecounter->cc);
  40 }
  41
  42 static bool timer_is_armed(struct arch_timer_cpu *timer)
  43 {
  44         return timer->armed;
  45 }
  46
  47 /* timer_arm: as in "arm the timer", not as in ARM the company */
  48 static void timer_arm(struct arch_timer_cpu *timer, u64 ns)
  49 {
  50         timer->armed = true;
  51         hrtimer_start(&timer->timer, ktime_add_ns(ktime_get(), ns),
  52                       HRTIMER_MODE_ABS);
  53 }
  54
  55 static void timer_disarm(struct arch_timer_cpu *timer)
  56 {
  57         if (timer_is_armed(timer)) {
  58                 hrtimer_cancel(&timer->timer);
  59                 cancel_work_sync(&timer->expired);
  60                 timer->armed = false;
  61         }
  62 }
  63
  64 static irqreturn_t kvm_arch_timer_handler(int irq, void *dev_id)
  65 {
  66         struct kvm_vcpu *vcpu = *(struct kvm_vcpu **)dev_id;
  67
  68         /*
  69          * We disable the timer in the world switch and let it be
  70          * handled by kvm_timer_sync_hwstate(). Getting a timer
  71          * interrupt at this point is a sure sign of some major
  72          * breakage.
  73          */
  74         pr_warn("Unexpected interrupt %d on vcpu %p\n", irq, vcpu);
  75         return IRQ_HANDLED;
  76 }
  77
  78 /*
  79  * Work function for handling the backup timer that we schedule when a vcpu is
  80  * no longer running, but had a timer programmed to fire in the future.
  81  */
  82 static void kvm_timer_inject_irq_work(struct work_struct *work)
  83 {
  84         struct kvm_vcpu *vcpu;
  85
  86         vcpu = container_of(work, struct kvm_vcpu, arch.timer_cpu.expired);
  87         vcpu->arch.timer_cpu.armed = false;
  88
  89         WARN_ON(!kvm_timer_should_fire(vcpu));
  90
  91         /*
  92          * If the vcpu is blocked we want to wake it up so that it will see
  93          * the timer has expired when entering the guest.
  94          */
  95         kvm_vcpu_kick(vcpu);
  96 }
  97
  98 static u64 kvm_timer_compute_delta(struct kvm_vcpu *vcpu)
  99 {
 100         cycle_t cval, now;
 101
 102         cval = vcpu->arch.timer_cpu.cntv_cval;
 103         now = kvm_phys_timer_read() - vcpu->kvm->arch.timer.cntvoff;
 104
 105         if (now < cval) {
 106                 u64 ns;
 107
 108                 ns = cyclecounter_cyc2ns(timecounter->cc,
 109                                          cval - now,
 110                                          timecounter->mask,
 111                                          &timecounter->frac);
 112                 return ns;
 113         }
 114
 115         return 0;
 116 }
 117
 118 static enum hrtimer_restart kvm_timer_expire(struct hrtimer *hrt)
 119 {
 120         struct arch_timer_cpu *timer;
 121         struct kvm_vcpu *vcpu;
 122         u64 ns;
 123
 124         timer = container_of(hrt, struct arch_timer_cpu, timer);
 125         vcpu = container_of(timer, struct kvm_vcpu, arch.timer_cpu);
 126
 127         /*
 128          * Check that the timer has really expired from the guest's
 129          * PoV (NTP on the host may have forced it to expire
 130          * early). If we should have slept longer, restart it.
 131          */
 132         ns = kvm_timer_compute_delta(vcpu);
 133         if (unlikely(ns)) {
 134                 hrtimer_forward_now(hrt, ns_to_ktime(ns));
 135                 return HRTIMER_RESTART;
 136         }
 137
 138         queue_work(wqueue, &timer->expired);
 139         return HRTIMER_NORESTART;
 140 }
 141
 142 static bool kvm_timer_irq_can_fire(struct kvm_vcpu *vcpu)
 143 {
 144         struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
 145
 146         return !(timer->cntv_ctl & ARCH_TIMER_CTRL_IT_MASK) &&
 147                 (timer->cntv_ctl & ARCH_TIMER_CTRL_ENABLE);
 148 }
 149
 150 bool kvm_timer_should_fire(struct kvm_vcpu *vcpu)
 151 {
 152         struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
 153         cycle_t cval, now;
 154
 155         if (!kvm_timer_irq_can_fire(vcpu))
 156                 return false;
 157
 158         cval = timer->cntv_cval;
 159         now = kvm_phys_timer_read() - vcpu->kvm->arch.timer.cntvoff;
 160
 161         return cval <= now;
 162 }
 163
 164 static void kvm_timer_update_irq(struct kvm_vcpu *vcpu, bool new_level)
 165 {
 166         int ret;
 167         struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
 168
 169         BUG_ON(!vgic_initialized(vcpu->kvm));
 170
 171         timer->irq.level = new_level;
 172         trace_kvm_timer_update_irq(vcpu->vcpu_id, timer->map->virt_irq,
 173                                    timer->irq.level);
 174         ret = kvm_vgic_inject_mapped_irq(vcpu->kvm, vcpu->vcpu_id,
 175                                          timer->map,
 176                                          timer->irq.level);
 177         WARN_ON(ret);
 178 }
 179
 180 /*
 181  * Check if there was a change in the timer state (should we raise or lower
 182  * the line level to the GIC).
 183  */
 184 static int kvm_timer_update_state(struct kvm_vcpu *vcpu)
 185 {
 186         struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
 187
 188         /*
 189          * If userspace modified the timer registers via SET_ONE_REG before
 190          * the vgic was initialized, we mustn't set the timer->irq.level value
 191          * because the guest would never see the interrupt.  Instead wait
 192          * until we call this function from kvm_timer_flush_hwstate.
 193          */
 194         if (!vgic_initialized(vcpu->kvm))
 195                 return -ENODEV;
 196
 197         if (kvm_timer_should_fire(vcpu) != timer->irq.level)
 198                 kvm_timer_update_irq(vcpu, !timer->irq.level);
 199
 200         return 0;
 201 }
 202
 203 /*
 204  * Schedule the background timer before calling kvm_vcpu_block, so that this
 205  * thread is removed from its waitqueue and made runnable when there's a timer
 206  * interrupt to handle.
 207  */
 208 void kvm_timer_schedule(struct kvm_vcpu *vcpu)
 209 {
 210         struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
 211
 212         BUG_ON(timer_is_armed(timer));
 213
 214         /*
 215          * No need to schedule a background timer if the guest timer has
 216          * already expired, because kvm_vcpu_block will return before putting
 217          * the thread to sleep.
 218          */
 219         if (kvm_timer_should_fire(vcpu))
 220                 return;
 221
 222         /*
 223          * If the timer is not capable of raising interrupts (disabled or
 224          * masked), then there's no more work for us to do.
 225          */
 226         if (!kvm_timer_irq_can_fire(vcpu))
 227                 return;
 228
 229         /*  The timer has not yet expired, schedule a background timer */
 230         timer_arm(timer, kvm_timer_compute_delta(vcpu));
 231 }
 232
 233 void kvm_timer_unschedule(struct kvm_vcpu *vcpu)
 234 {
 235         struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
 236         timer_disarm(timer);
 237 }
 238
 239 /**
 240  * kvm_timer_flush_hwstate - prepare to move the virt timer to the cpu
 241  * @vcpu: The vcpu pointer
 242  *
 243  * Check if the virtual timer has expired while we were running in the host,
 244  * and inject an interrupt if that was the case.
 245  */
 246 void kvm_timer_flush_hwstate(struct kvm_vcpu *vcpu)
 247 {
 248         struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
 249         bool phys_active;
 250         int ret;
 251
 252         if (kvm_timer_update_state(vcpu))
 253                 return;
 254
 255         /*
 256         * If we enter the guest with the virtual input level to the VGIC
 257         * asserted, then we have already told the VGIC what we need to, and
 258         * we don't need to exit from the guest until the guest deactivates
 259         * the already injected interrupt, so therefore we should set the
 260         * hardware active state to prevent unnecessary exits from the guest.
 261         *
 262         * Also, if we enter the guest with the virtual timer interrupt active,
 263         * then it must be active on the physical distributor, because we set
 264         * the HW bit and the guest must be able to deactivate the virtual and
 265         * physical interrupt at the same time.
 266         *
 267         * Conversely, if the virtual input level is deasserted and the virtual
 268         * interrupt is not active, then always clear the hardware active state
 269         * to ensure that hardware interrupts from the timer triggers a guest
 270         * exit.
 271         */
 272         if (timer->irq.level || kvm_vgic_map_is_active(vcpu, timer->map))
 273                 phys_active = true;
 274         else
 275                 phys_active = false;
 276
 277         ret = irq_set_irqchip_state(timer->map->irq,
 278                                     IRQCHIP_STATE_ACTIVE,
 279                                     phys_active);
 280         WARN_ON(ret);
 281 }
 282
 283 /**
 284  * kvm_timer_sync_hwstate - sync timer state from cpu
 285  * @vcpu: The vcpu pointer
 286  *
 287  * Check if the virtual timer has expired while we were running in the guest,
 288  * and inject an interrupt if that was the case.
 289  */
 290 void kvm_timer_sync_hwstate(struct kvm_vcpu *vcpu)
 291 {
 292         struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
 293
 294         BUG_ON(timer_is_armed(timer));
 295
 296         /*
 297          * The guest could have modified the timer registers or the timer
 298          * could have expired, update the timer state.
 299          */
 300         kvm_timer_update_state(vcpu);
 301 }
 302
 303 int kvm_timer_vcpu_reset(struct kvm_vcpu *vcpu,
 304                          const struct kvm_irq_level *irq)
 305 {
 306         struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
 307         struct irq_phys_map *map;
 308
 309         /*
 310          * The vcpu timer irq number cannot be determined in
 311          * kvm_timer_vcpu_init() because it is called much before
 312          * kvm_vcpu_set_target(). To handle this, we determine
 313          * vcpu timer irq number when the vcpu is reset.
 314          */
 315         timer->irq.irq = irq->irq;
 316
 317         /*
 318          * The bits in CNTV_CTL are architecturally reset to UNKNOWN for ARMv8
 319          * and to 0 for ARMv7.  We provide an implementation that always
 320          * resets the timer to be disabled and unmasked and is compliant with
 321          * the ARMv7 architecture.
 322          */
 323         timer->cntv_ctl = 0;
 324         kvm_timer_update_state(vcpu);
 325
 326         /*
 327          * Tell the VGIC that the virtual interrupt is tied to a
 328          * physical interrupt. We do that once per VCPU.
 329          */
 330         map = kvm_vgic_map_phys_irq(vcpu, irq->irq, host_vtimer_irq);
 331         if (WARN_ON(IS_ERR(map)))
 332                 return PTR_ERR(map);
 333
 334         timer->map = map;
 335         return 0;
 336 }
 337
 338 void kvm_timer_vcpu_init(struct kvm_vcpu *vcpu)
 339 {
 340         struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
 341
 342         INIT_WORK(&timer->expired, kvm_timer_inject_irq_work);
 343         hrtimer_init(&timer->timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
 344         timer->timer.function = kvm_timer_expire;
 345 }
 346
 347 static void kvm_timer_init_interrupt(void *info)
 348 {
 349         enable_percpu_irq(host_vtimer_irq, 0);
 350 }
 351
 352 int kvm_arm_timer_set_reg(struct kvm_vcpu *vcpu, u64 regid, u64 value)
 353 {
 354         struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
 355
 356         switch (regid) {
 357         case KVM_REG_ARM_TIMER_CTL:
 358                 timer->cntv_ctl = value;
 359                 break;
 360         case KVM_REG_ARM_TIMER_CNT:
 361                 vcpu->kvm->arch.timer.cntvoff = kvm_phys_timer_read() - value;
 362                 break;
 363         case KVM_REG_ARM_TIMER_CVAL:
 364                 timer->cntv_cval = value;
 365                 break;
 366         default:
 367                 return -1;
 368         }
 369
 370         kvm_timer_update_state(vcpu);
 371         return 0;
 372 }
 373
 374 u64 kvm_arm_timer_get_reg(struct kvm_vcpu *vcpu, u64 regid)
 375 {
 376         struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
 377
 378         switch (regid) {
 379         case KVM_REG_ARM_TIMER_CTL:
 380                 return timer->cntv_ctl;
 381         case KVM_REG_ARM_TIMER_CNT:
 382                 return kvm_phys_timer_read() - vcpu->kvm->arch.timer.cntvoff;
 383         case KVM_REG_ARM_TIMER_CVAL:
 384                 return timer->cntv_cval;
 385         }
 386         return (u64)-1;
 387 }
 388
 389 static int kvm_timer_cpu_notify(struct notifier_block *self,
 390                                 unsigned long action, void *cpu)
 391 {
 392         switch (action) {
 393         case CPU_STARTING:
 394         case CPU_STARTING_FROZEN:
 395                 kvm_timer_init_interrupt(NULL);
 396                 break;
 397         case CPU_DYING:
 398         case CPU_DYING_FROZEN:
 399                 disable_percpu_irq(host_vtimer_irq);
 400                 break;
 401         }
 402
 403         return NOTIFY_OK;
 404 }
 405
 406 static struct notifier_block kvm_timer_cpu_nb = {
 407         .notifier_call = kvm_timer_cpu_notify,
 408 };
 409
 410 static const struct of_device_id arch_timer_of_match[] = {
 411         { .compatible   = "arm,armv7-timer",    },
 412         { .compatible   = "arm,armv8-timer",    },
 413         {},
 414 };
 415
 416 int kvm_timer_hyp_init(void)
 417 {
 418         struct device_node *np;
 419         unsigned int ppi;
 420         int err;
 421
 422         timecounter = arch_timer_get_timecounter();
 423         if (!timecounter)
 424                 return -ENODEV;
 425
 426         np = of_find_matching_node(NULL, arch_timer_of_match);
 427         if (!np) {
 428                 kvm_err("kvm_arch_timer: can't find DT node\n");
 429                 return -ENODEV;
 430         }
 431
 432         ppi = irq_of_parse_and_map(np, 2);
 433         if (!ppi) {
 434                 kvm_err("kvm_arch_timer: no virtual timer interrupt\n");
 435                 err = -EINVAL;
 436                 goto out;
 437         }
 438
 439         err = request_percpu_irq(ppi, kvm_arch_timer_handler,
 440                                  "kvm guest timer", kvm_get_running_vcpus());
 441         if (err) {
 442                 kvm_err("kvm_arch_timer: can't request interrupt %d (%d)\n",
 443                         ppi, err);
 444                 goto out;
 445         }
 446
 447         host_vtimer_irq = ppi;
 448
 449         err = __register_cpu_notifier(&kvm_timer_cpu_nb);
 450         if (err) {
 451                 kvm_err("Cannot register timer CPU notifier\n");
 452                 goto out_free;
 453         }
 454
 455         wqueue = create_singlethread_workqueue("kvm_arch_timer");
 456         if (!wqueue) {
 457                 err = -ENOMEM;
 458                 goto out_free;
 459         }
 460
 461         kvm_info("%s IRQ%d\n", np->name, ppi);
 462         on_each_cpu(kvm_timer_init_interrupt, NULL, 1);
 463
 464         goto out;
 465 out_free:
 466         free_percpu_irq(ppi, kvm_get_running_vcpus());
 467 out:
 468         of_node_put(np);
 469         return err;
 470 }
 471
 472 void kvm_timer_vcpu_terminate(struct kvm_vcpu *vcpu)
 473 {
 474         struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
 475
 476         timer_disarm(timer);
 477         if (timer->map)
 478                 kvm_vgic_unmap_phys_irq(vcpu, timer->map);
 479 }
 480
 481 void kvm_timer_enable(struct kvm *kvm)
 482 {
 483         if (kvm->arch.timer.enabled)
 484                 return;
 485
 486         /*
 487          * There is a potential race here between VCPUs starting for the first
 488          * time, which may be enabling the timer multiple times.  That doesn't
 489          * hurt though, because we're just setting a variable to the same
 490          * variable that it already was.  The important thing is that all
 491          * VCPUs have the enabled variable set, before entering the guest, if
 492          * the arch timers are enabled.
 493          */
 494         if (timecounter && wqueue)
 495                 kvm->arch.timer.enabled = 1;
 496 }
 497
 498 void kvm_timer_init(struct kvm *kvm)
 499 {
 500         kvm->arch.timer.cntvoff = kvm_phys_timer_read();
 501 }