KVM: PPC: Convert DSISR to shared page

The DSISR register contains information about a data page fault. It is fully
read/write from inside the guest context and we don't need to worry about
interacting based on writes of this register.

This patch converts all users of the current field to the shared page.

Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/arch/powerpc/kvm/book3s_emulate.c b/arch/powerpc/kvm/book3s_emulate.c
index 35d3c16..9982ff1 100644
--- a/arch/powerpc/kvm/book3s_emulate.c
+++ b/arch/powerpc/kvm/book3s_emulate.c
@@ -221,7 +221,7 @@
 				else if (r == -EPERM)
 					dsisr |= DSISR_PROTFAULT;
 
-				to_book3s(vcpu)->dsisr = dsisr;
+				vcpu->arch.shared->dsisr = dsisr;
 				to_svcpu(vcpu)->fault_dsisr = dsisr;
 
 				kvmppc_book3s_queue_irqprio(vcpu,
@@ -327,7 +327,7 @@
 		to_book3s(vcpu)->sdr1 = spr_val;
 		break;
 	case SPRN_DSISR:
-		to_book3s(vcpu)->dsisr = spr_val;
+		vcpu->arch.shared->dsisr = spr_val;
 		break;
 	case SPRN_DAR:
 		vcpu->arch.dear = spr_val;
@@ -440,7 +440,7 @@
 		kvmppc_set_gpr(vcpu, rt, to_book3s(vcpu)->sdr1);
 		break;
 	case SPRN_DSISR:
-		kvmppc_set_gpr(vcpu, rt, to_book3s(vcpu)->dsisr);
+		kvmppc_set_gpr(vcpu, rt, vcpu->arch.shared->dsisr);
 		break;
 	case SPRN_DAR:
 		kvmppc_set_gpr(vcpu, rt, vcpu->arch.dear);