KVM: s390: provide CMMA attributes only if available

Let's not provide the device attribute for cmma enabling and clearing
if the hardware doesn't support it.

This also helps getting rid of the undocumented return value "-EINVAL"
in case CMMA is not available when trying to enable it.

Also properly document the meaning of -EINVAL for CMMA clearing.

Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

1 files changed, 6 insertions, 1 deletions

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 005e664f6360..f695c6e08337 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -485,7 +485,7 @@ static int kvm_s390_set_mem_control(struct kvm *kvm, struct kvm_device_attr *att
         unsigned int idx;
         switch (attr->attr) {
         case KVM_S390_VM_MEM_ENABLE_CMMA:
-                ret = -EINVAL;
+                ret = -ENXIO;
                 if (!sclp.has_cmma)
                         break;
 
@@ -499,6 +499,9 @@ static int kvm_s390_set_mem_control(struct kvm *kvm, struct kvm_device_attr *att
                 mutex_unlock(&kvm->lock);
                 break;
         case KVM_S390_VM_MEM_CLR_CMMA:
+                ret = -ENXIO;
+                if (!sclp.has_cmma)
+                        break;
                 ret = -EINVAL;
                 if (!kvm->arch.use_cmma)
                         break;
@@ -964,6 +967,8 @@ static int kvm_s390_vm_has_attr(struct kvm *kvm, struct kvm_device_attr *attr)
                 switch (attr->attr) {
                 case KVM_S390_VM_MEM_ENABLE_CMMA:
                 case KVM_S390_VM_MEM_CLR_CMMA:
+                        ret = sclp.has_cmma ? 0 : -ENXIO;
+                        break;
                 case KVM_S390_VM_MEM_LIMIT_SIZE:
                         ret = 0;
                         break;