KVM: PPC: Check privilege level on SPRs

We have 3 privilege levels: problem state, supervisor state and hypervisor
state. Each of them can access different SPRs, so we need to check on every
SPR if it's accessible in the respective mode.

Signed-off-by: Alexander Graf <[e-mail]>

arch/powerpc/kvm/book3s_emulate.c

···
  * function pointers, so let's just disable the define. */
 #undef mfsrin
 
+enum priv_level {
+	PRIV_PROBLEM = 0,
+	PRIV_SUPER = 1,
+	PRIV_HYPER = 2,
+};
+
+static bool spr_allowed(struct kvm_vcpu *vcpu, enum priv_level level)
+{
+	/* PAPR VMs only access supervisor SPRs */
+	if (vcpu->arch.papr_enabled && (level > PRIV_SUPER))
+		return false;
+
+	/* Limit user space to its own small SPR set */
+	if ((vcpu->arch.shared->msr & MSR_PR) && level > PRIV_PROBLEM)
+		return false;
+
+	return true;
+}
+
 int kvmppc_core_emulate_op(struct kvm_run *run, struct kvm_vcpu *vcpu,
                            unsigned int inst, int *advance)
 {
···
 
 	switch (sprn) {
 	case SPRN_SDR1:
+		if (!spr_allowed(vcpu, PRIV_HYPER))
+			goto unprivileged;
 		to_book3s(vcpu)->sdr1 = spr_val;
 		break;
 	case SPRN_DSISR:
···
 	case SPRN_PMC4_GEKKO:
 	case SPRN_WPAR_GEKKO:
 		break;
+unprivileged:
 	default:
 		printk(KERN_INFO "KVM: invalid SPR write: %d\n", sprn);
 #ifndef DEBUG_SPR
···
 		break;
 	}
 	case SPRN_SDR1:
+		if (!spr_allowed(vcpu, PRIV_HYPER))
+			goto unprivileged;
 		kvmppc_set_gpr(vcpu, rt, to_book3s(vcpu)->sdr1);
 		break;
 	case SPRN_DSISR:
···
 		kvmppc_set_gpr(vcpu, rt, 0);
 		break;
 	default:
+unprivileged:
 		printk(KERN_INFO "KVM: invalid SPR read: %d\n", sprn);
 #ifndef DEBUG_SPR
 		emulated = EMULATE_FAIL;