LoongArch: KVM: Make function kvm_own_lbt() robust

commit 4be8cef upstream.

Add the flag KVM_LARCH_LBT checking in function kvm_own_lbt(), so that
it can be called safely rather than duplicated enabling again.

Cc: stable@vger.kernel.org
Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: bibo-mao

arch/loongarch/kvm/vcpu.c

@@ -1277,9 +1277,11 @@ int kvm_own_lbt(struct kvm_vcpu *vcpu)
 		return -EINVAL;
 
 	preempt_disable();
-	set_csr_euen(CSR_EUEN_LBTEN);
-	_restore_lbt(&vcpu->arch.lbt);
-	vcpu->arch.aux_inuse |= KVM_LARCH_LBT;
+	if (!(vcpu->arch.aux_inuse & KVM_LARCH_LBT)) {
+		set_csr_euen(CSR_EUEN_LBTEN);
+		_restore_lbt(&vcpu->arch.lbt);
+		vcpu->arch.aux_inuse |= KVM_LARCH_LBT;
+	}
 	preempt_enable();
 
 	return 0;