KVM: PPC: booke: Improve timer register emulation

Decrementers are now properly driven by TCR/TSR, and the guest
has full read/write access to these registers.

The decrementer keeps ticking (and setting the TSR bit) regardless of
whether the interrupts are enabled with TCR.

The decrementer stops at zero, rather than going negative.

Decrementers (and FITs, once implemented) are delivered as
level-triggered interrupts -- dequeued when the TSR bit is cleared, not
on delivery.

Signed-off-by: Liu Yu <yu.liu@freescale.com>
[scottwood@freescale.com: significant changes]
Signed-off-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 51 insertions, 16 deletions

diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
index 50803dd0b8f2..9e41f45d07ed 100644
--- a/arch/powerpc/kvm/booke.c
+++ b/arch/powerpc/kvm/booke.c
@@ -252,9 +252,11 @@ static int kvmppc_booke_irqprio_deliver(struct kvm_vcpu *vcpu,
 		allowed = vcpu->arch.shared->msr & MSR_ME;
 		msr_mask = 0;
 		break;
-	case BOOKE_IRQPRIO_EXTERNAL:
 	case BOOKE_IRQPRIO_DECREMENTER:
 	case BOOKE_IRQPRIO_FIT:
+		keep_irq = true;
+		/* fall through */
+	case BOOKE_IRQPRIO_EXTERNAL:
 		allowed = vcpu->arch.shared->msr & MSR_EE;
 		allowed = allowed && !crit;
 		msr_mask = MSR_CE|MSR_ME|MSR_DE;
@@ -282,11 +284,26 @@ static int kvmppc_booke_irqprio_deliver(struct kvm_vcpu *vcpu,
 	return allowed;
 }
 
+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);
+}
+
 static void kvmppc_core_check_exceptions(struct kvm_vcpu *vcpu)
 {
 	unsigned long *pending = &vcpu->arch.pending_exceptions;
 	unsigned int priority;
 
+	if (vcpu->requests) {
+		if (kvm_check_request(KVM_REQ_PENDING_TIMER, vcpu)) {
+			smp_mb();
+			update_timer_ints(vcpu);
+		}
+	}
+
 	priority = __ffs(*pending);
 	while (priority <= BOOKE_IRQPRIO_MAX) {
 		if (kvmppc_booke_irqprio_deliver(vcpu, priority))
@@ -749,25 +766,16 @@ static int set_sregs_base(struct kvm_vcpu *vcpu,
 	vcpu->arch.shared->esr = sregs->u.e.esr;
 	vcpu->arch.shared->dar = sregs->u.e.dear;
 	vcpu->arch.vrsave = sregs->u.e.vrsave;
-	vcpu->arch.tcr = sregs->u.e.tcr;
+	kvmppc_set_tcr(vcpu, sregs->u.e.tcr);
 
-	if (sregs->u.e.update_special & KVM_SREGS_E_UPDATE_DEC)
+	if (sregs->u.e.update_special & KVM_SREGS_E_UPDATE_DEC) {
 		vcpu->arch.dec = sregs->u.e.dec;
-
-	kvmppc_emulate_dec(vcpu);
+		kvmppc_emulate_dec(vcpu);
+	}
 
 	if (sregs->u.e.update_special & KVM_SREGS_E_UPDATE_TSR) {
-		/*
-		 * FIXME: existing KVM timer handling is incomplete.
-		 * TSR cannot be read by the guest, and its value in
-		 * vcpu->arch is always zero.  For now, just handle
-		 * the case where the caller is trying to inject a
-		 * decrementer interrupt.
-		 */
-
-		if ((sregs->u.e.tsr & TSR_DIS) &&
-		    (vcpu->arch.tcr & TCR_DIE))
-			kvmppc_core_queue_dec(vcpu);
+		vcpu->arch.tsr = sregs->u.e.tsr;
+		update_timer_ints(vcpu);
 	}
 
 	return 0;
@@ -923,6 +931,33 @@ void kvmppc_core_destroy_vm(struct kvm *kvm)
 {
 }
 
+void kvmppc_set_tcr(struct kvm_vcpu *vcpu, u32 new_tcr)
+{
+	vcpu->arch.tcr = new_tcr;
+	update_timer_ints(vcpu);
+}
+
+void kvmppc_set_tsr_bits(struct kvm_vcpu *vcpu, u32 tsr_bits)
+{
+	set_bits(tsr_bits, &vcpu->arch.tsr);
+	smp_wmb();
+	kvm_make_request(KVM_REQ_PENDING_TIMER, vcpu);
+	kvm_vcpu_kick(vcpu);
+}
+
+void kvmppc_clr_tsr_bits(struct kvm_vcpu *vcpu, u32 tsr_bits)
+{
+	clear_bits(tsr_bits, &vcpu->arch.tsr);
+	update_timer_ints(vcpu);
+}
+
+void kvmppc_decrementer_func(unsigned long data)
+{
+	struct kvm_vcpu *vcpu = (struct kvm_vcpu *)data;
+
+	kvmppc_set_tsr_bits(vcpu, TSR_DIS);
+}
+
 int __init kvmppc_booke_init(void)
 {
 	unsigned long ivor[16];