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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>
This commit is contained in:
David Hildenbrand 2016-03-03 09:48:47 +01:00 committed by Christian Borntraeger
parent c24cc9c8a6
commit f9cbd9b025
3 changed files with 10 additions and 2 deletions
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2
Documentation/virtual/kvm/api.txt
View File

@ -2520,6 +2520,7 @@ Parameters: struct kvm_device_attr
Returns: 0 on success, -1 on error
Errors:
ENXIO: The group or attribute is unknown/unsupported for this device
or hardware support is missing.
EPERM: The attribute cannot (currently) be accessed this way
(e.g. read-only attribute, or attribute that only makes
sense when the device is in a different state)
@ -2547,6 +2548,7 @@ Parameters: struct kvm_device_attr
Returns: 0 on success, -1 on error
Errors:
ENXIO: The group or attribute is unknown/unsupported for this device
or hardware support is missing.
Tests whether a device supports a particular attribute. A successful
return indicates the attribute is implemented. It does not necessarily

3
Documentation/virtual/kvm/devices/vm.txt
View File

@ -20,7 +20,8 @@ Enables Collaborative Memory Management Assist (CMMA) for the virtual machine.
1.2. ATTRIBUTE: KVM_S390_VM_MEM_CLR_CMMA
Parameters: none
Returns: 0
Returns: -EINVAL if CMMA was not enabled
0 otherwise
Clear the CMMA status for all guest pages, so any pages the guest marked
as unused are again used any may not be reclaimed by the host.

7
arch/s390/kvm/kvm-s390.c
View File

@ -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;