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>

arch/powerpc/kvm/booke_emulate.c

@@ -13,6 +13,7 @@
  * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  *
  * Copyright IBM Corp. 2008
+ * Copyright 2011 Freescale Semiconductor, Inc.
  *
  * Authors: Hollis Blanchard <hollisb@us.ibm.com>
  */
@@ -115,10 +116,10 @@ int kvmppc_booke_emulate_mtspr(struct kvm_vcpu *vcpu, int sprn, int rs)
 	case SPRN_DBSR:
 		vcpu->arch.dbsr &= ~spr_val; break;
 	case SPRN_TSR:
-		vcpu->arch.tsr &= ~spr_val; break;
+		kvmppc_clr_tsr_bits(vcpu, spr_val);
+		break;
 	case SPRN_TCR:
-		vcpu->arch.tcr = spr_val;
-		kvmppc_emulate_dec(vcpu);
+		kvmppc_set_tcr(vcpu, spr_val);
 		break;
 
 	/* Note: SPRG4-7 are user-readable. These values are
@@ -209,6 +210,10 @@ int kvmppc_booke_emulate_mfspr(struct kvm_vcpu *vcpu, int sprn, int rt)
 		kvmppc_set_gpr(vcpu, rt, vcpu->arch.dbcr1); break;
 	case SPRN_DBSR:
 		kvmppc_set_gpr(vcpu, rt, vcpu->arch.dbsr); break;
+	case SPRN_TSR:
+		kvmppc_set_gpr(vcpu, rt, vcpu->arch.tsr); break;
+	case SPRN_TCR:
+		kvmppc_set_gpr(vcpu, rt, vcpu->arch.tcr); break;
 
 	case SPRN_IVOR0:
 		kvmppc_set_gpr(vcpu, rt, vcpu->arch.ivor[BOOKE_IRQPRIO_CRITICAL]);