+/*
+ * Return the number of jiffies until the next timeout. If the timeout is
+ * longer than the NEXT_TIMER_MAX_DELTA, then return NEXT_TIMER_MAX_DELTA
+ * because the larger value can break the timer APIs.
+ */
+static unsigned long watchdog_next_timeout(struct kvm_vcpu *vcpu)
+{
+ u64 tb, wdt_tb, wdt_ticks = 0;
+ u64 nr_jiffies = 0;
+ u32 period = TCR_GET_WP(vcpu->arch.tcr);
+
+ wdt_tb = 1ULL << (63 - period);
+ tb = get_tb();
+ /*
+ * The watchdog timeout will hapeen when TB bit corresponding
+ * to watchdog will toggle from 0 to 1.
+ */
+ if (tb & wdt_tb)
+ wdt_ticks = wdt_tb;
+
+ wdt_ticks += wdt_tb - (tb & (wdt_tb - 1));
+
+ /* Convert timebase ticks to jiffies */
+ nr_jiffies = wdt_ticks;
+
+ if (do_div(nr_jiffies, tb_ticks_per_jiffy))
+ nr_jiffies++;
+
+ return min_t(unsigned long long, nr_jiffies, NEXT_TIMER_MAX_DELTA);
+}
+
+static void arm_next_watchdog(struct kvm_vcpu *vcpu)
+{
+ unsigned long nr_jiffies;
+ unsigned long flags;
+
+ /*
+ * If TSR_ENW and TSR_WIS are not set then no need to exit to
+ * userspace, so clear the KVM_REQ_WATCHDOG request.
+ */
+ if ((vcpu->arch.tsr & (TSR_ENW | TSR_WIS)) != (TSR_ENW | TSR_WIS))
+ clear_bit(KVM_REQ_WATCHDOG, &vcpu->requests);
+
+ spin_lock_irqsave(&vcpu->arch.wdt_lock, flags);
+ nr_jiffies = watchdog_next_timeout(vcpu);
+ /*
+ * If the number of jiffies of watchdog timer >= NEXT_TIMER_MAX_DELTA
+ * then do not run the watchdog timer as this can break timer APIs.
+ */
+ if (nr_jiffies < NEXT_TIMER_MAX_DELTA)
+ mod_timer(&vcpu->arch.wdt_timer, jiffies + nr_jiffies);
+ else
+ del_timer(&vcpu->arch.wdt_timer);
+ spin_unlock_irqrestore(&vcpu->arch.wdt_lock, flags);
+}
+
+void kvmppc_watchdog_func(unsigned long data)
+{
+ struct kvm_vcpu *vcpu = (struct kvm_vcpu *)data;
+ u32 tsr, new_tsr;
+ int final;
+
+ do {
+ new_tsr = tsr = vcpu->arch.tsr;
+ final = 0;
+
+ /* Time out event */
+ if (tsr & TSR_ENW) {
+ if (tsr & TSR_WIS)
+ final = 1;
+ else
+ new_tsr = tsr | TSR_WIS;
+ } else {
+ new_tsr = tsr | TSR_ENW;
+ }
+ } while (cmpxchg(&vcpu->arch.tsr, tsr, new_tsr) != tsr);
+
+ if (new_tsr & TSR_WIS) {
+ smp_wmb();
+ kvm_make_request(KVM_REQ_PENDING_TIMER, vcpu);
+ kvm_vcpu_kick(vcpu);
+ }
+
+ /*
+ * If this is final watchdog expiry and some action is required
+ * then exit to userspace.
+ */
+ if (final && (vcpu->arch.tcr & TCR_WRC_MASK) &&
+ vcpu->arch.watchdog_enabled) {
+ smp_wmb();
+ kvm_make_request(KVM_REQ_WATCHDOG, vcpu);
+ kvm_vcpu_kick(vcpu);
+ }
+
+ /*
+ * Stop running the watchdog timer after final expiration to
+ * prevent the host from being flooded with timers if the
+ * guest sets a short period.
+ * Timers will resume when TSR/TCR is updated next time.
+ */
+ if (!final)
+ arm_next_watchdog(vcpu);
+}
+