KVM: PPC: booke: Add watchdog emulation

This patch adds the watchdog emulation in KVM. The watchdog
emulation is enabled by KVM_ENABLE_CAP(KVM_CAP_PPC_BOOKE_WATCHDOG) ioctl.
The kernel timer are used for watchdog emulation and emulates
h/w watchdog state machine. On watchdog timer expiry, it exit to QEMU
if TCR.WRC is non ZERO. QEMU can reset/shutdown etc depending upon how
it is configured.

Signed-off-by: Liu Yu <yu.liu@freescale.com>
Signed-off-by: Scott Wood <scottwood@freescale.com>
[bharat.bhushan@freescale.com: reworked patch]
Signed-off-by: Bharat Bhushan <bharat.bhushan@freescale.com>
[agraf: adjust to new request framework]
Signed-off-by: Alexander Graf <agraf@suse.de>

1 files changed, 155 insertions, 0 deletions

diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
index c36493087dbf..09e8bf33a8c9 100644
--- a/arch/powerpc/kvm/booke.c
+++ b/arch/powerpc/kvm/booke.c
@@ -209,6 +209,16 @@ void kvmppc_core_dequeue_external(struct kvm_vcpu *vcpu,
 	clear_bit(BOOKE_IRQPRIO_EXTERNAL_LEVEL, &vcpu->arch.pending_exceptions);
 }
 
+static void kvmppc_core_queue_watchdog(struct kvm_vcpu *vcpu)
+{
+	kvmppc_booke_queue_irqprio(vcpu, BOOKE_IRQPRIO_WATCHDOG);
+}
+
+static void kvmppc_core_dequeue_watchdog(struct kvm_vcpu *vcpu)
+{
+	clear_bit(BOOKE_IRQPRIO_WATCHDOG, &vcpu->arch.pending_exceptions);
+}
+
 static void set_guest_srr(struct kvm_vcpu *vcpu, unsigned long srr0, u32 srr1)
 {
 #ifdef CONFIG_KVM_BOOKE_HV
@@ -328,6 +338,7 @@ static int kvmppc_booke_irqprio_deliver(struct kvm_vcpu *vcpu,
 		msr_mask = MSR_CE | MSR_ME | MSR_DE;
 		int_class = INT_CLASS_NONCRIT;
 		break;
+	case BOOKE_IRQPRIO_WATCHDOG:
 	case BOOKE_IRQPRIO_CRITICAL:
 	case BOOKE_IRQPRIO_DBELL_CRIT:
 		allowed = vcpu->arch.shared->msr & MSR_CE;
@@ -407,12 +418,121 @@ static int kvmppc_booke_irqprio_deliver(struct kvm_vcpu *vcpu,
 	return allowed;
 }
 
+/*
+ * 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);
+}
+
 static void update_timer_ints(struct kvm_vcpu *vcpu)
 {
 	if ((vcpu->arch.tcr & TCR_DIE) && (vcpu->arch.tsr & TSR_DIS))
 		kvmppc_core_queue_dec(vcpu);
 	else
 		kvmppc_core_dequeue_dec(vcpu);
+
+	if ((vcpu->arch.tcr & TCR_WIE) && (vcpu->arch.tsr & TSR_WIS))
+		kvmppc_core_queue_watchdog(vcpu);
+	else
+		kvmppc_core_dequeue_watchdog(vcpu);
 }
 
 static void kvmppc_core_check_exceptions(struct kvm_vcpu *vcpu)
@@ -466,6 +586,11 @@ int kvmppc_core_check_requests(struct kvm_vcpu *vcpu)
 		kvmppc_core_flush_tlb(vcpu);
 #endif
 
+	if (kvm_check_request(KVM_REQ_WATCHDOG, vcpu)) {
+		vcpu->run->exit_reason = KVM_EXIT_WATCHDOG;
+		r = 0;
+	}
+
 	return r;
 }
 
@@ -995,6 +1120,21 @@ int kvm_arch_vcpu_setup(struct kvm_vcpu *vcpu)
 	return r;
 }
 
+int kvmppc_subarch_vcpu_init(struct kvm_vcpu *vcpu)
+{
+	/* setup watchdog timer once */
+	spin_lock_init(&vcpu->arch.wdt_lock);
+	setup_timer(&vcpu->arch.wdt_timer, kvmppc_watchdog_func,
+		    (unsigned long)vcpu);
+
+	return 0;
+}
+
+void kvmppc_subarch_vcpu_uninit(struct kvm_vcpu *vcpu)
+{
+	del_timer_sync(&vcpu->arch.wdt_timer);
+}
+
 int kvm_arch_vcpu_ioctl_get_regs(struct kvm_vcpu *vcpu, struct kvm_regs *regs)
 {
 	int i;
@@ -1090,7 +1230,13 @@ static int set_sregs_base(struct kvm_vcpu *vcpu,
 	}
 
 	if (sregs->u.e.update_special & KVM_SREGS_E_UPDATE_TSR) {
+		u32 old_tsr = vcpu->arch.tsr;
+
 		vcpu->arch.tsr = sregs->u.e.tsr;
+
+		if ((old_tsr ^ vcpu->arch.tsr) & (TSR_ENW | TSR_WIS))
+			arm_next_watchdog(vcpu);
+
 		update_timer_ints(vcpu);
 	}
 
@@ -1251,6 +1397,7 @@ void kvmppc_core_commit_memory_region(struct kvm *kvm,
 void kvmppc_set_tcr(struct kvm_vcpu *vcpu, u32 new_tcr)
 {
 	vcpu->arch.tcr = new_tcr;
+	arm_next_watchdog(vcpu);
 	update_timer_ints(vcpu);
 }
 
@@ -1265,6 +1412,14 @@ void kvmppc_set_tsr_bits(struct kvm_vcpu *vcpu, u32 tsr_bits)
 void kvmppc_clr_tsr_bits(struct kvm_vcpu *vcpu, u32 tsr_bits)
 {
 	clear_bits(tsr_bits, &vcpu->arch.tsr);
+
+	/*
+	 * We may have stopped the watchdog due to
+	 * being stuck on final expiration.
+	 */
+	if (tsr_bits & (TSR_ENW | TSR_WIS))
+		arm_next_watchdog(vcpu);
+
 	update_timer_ints(vcpu);
 }