KVM: PPC: Book3S HV: Reject mflags=2 (LPCR[AIL]=2) ADDR_TRANS_MODE mode

AIL=2 mode has no known users, so is not well tested or supported.
Disallow guests from selecting this mode because it may become
deprecated in future versions of the architecture.

This policy decision is not left to QEMU because KVM support is
required for AIL=2 (when injecting interrupts).
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

arch/powerpc/kvm/book3s_hv.c

@@ -779,6 +779,11 @@ static int kvmppc_h_set_mode(struct kvm_vcpu *vcpu, unsigned long mflags,
 		vcpu->arch.dawr  = value1;
 		vcpu->arch.dawrx = value2;
 		return H_SUCCESS;
+	case H_SET_MODE_RESOURCE_ADDR_TRANS_MODE:
+		/* KVM does not support mflags=2 (AIL=2) */
+		if (mflags != 0 && mflags != 3)
+			return H_UNSUPPORTED_FLAG_START;
+		return H_TOO_HARD;
 	default:
 		return H_TOO_HARD;
 	}