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Commit f9cbd9b0 authored by David Hildenbrand's avatar David Hildenbrand Committed by Christian Borntraeger
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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: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: default avatarDavid Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
parent c24cc9c8

Documentation/virtual/kvm/api.txt

+2 −0
Original line number Original line Diff line number Diff line
@@ -2520,6 +2520,7 @@ Parameters: struct kvm_device_attr 
Returns: 0 on success, -1 on error

Returns: 0 on success, -1 on error

Errors:

Errors:

  ENXIO:  The group or attribute is unknown/unsupported for this device

  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

  EPERM:  The attribute cannot (currently) be accessed this way

          (e.g. read-only attribute, or attribute that only makes

          (e.g. read-only attribute, or attribute that only makes

          sense when the device is in a different state)

          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

Returns: 0 on success, -1 on error

Errors:

Errors:

  ENXIO:  The group or attribute is unknown/unsupported for this device

  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

Tests whether a device supports a particular attribute.  A successful

return indicates the attribute is implemented.  It does not necessarily

return indicates the attribute is implemented.  It does not necessarily

Documentation/virtual/kvm/devices/vm.txt

+2 −1
Original line number Original line Diff line number Diff line
@@ -20,7 +20,8 @@ Enables Collaborative Memory Management Assist (CMMA) for the virtual machine. 




1.2. ATTRIBUTE: KVM_S390_VM_MEM_CLR_CMMA

1.2. ATTRIBUTE: KVM_S390_VM_MEM_CLR_CMMA

Parameters: none

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

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.

as unused are again used any may not be reclaimed by the host.

arch/s390/kvm/kvm-s390.c

+6 −1
Original line number Original line Diff line number Diff line
@@ -485,7 +485,7 @@ static int kvm_s390_set_mem_control(struct kvm *kvm, struct kvm_device_attr *att 
	unsigned int idx;

	unsigned int idx;

	switch (attr->attr) {

	switch (attr->attr) {

	case KVM_S390_VM_MEM_ENABLE_CMMA:

	case KVM_S390_VM_MEM_ENABLE_CMMA:

		ret = -EINVAL;

		ret = -ENXIO;

		if (!sclp.has_cmma)

		if (!sclp.has_cmma)

			break;

			break;
@@ -499,6 +499,9 @@ static int kvm_s390_set_mem_control(struct kvm *kvm, struct kvm_device_attr *att 
		mutex_unlock(&kvm->lock);

		mutex_unlock(&kvm->lock);

		break;

		break;

	case KVM_S390_VM_MEM_CLR_CMMA:

	case KVM_S390_VM_MEM_CLR_CMMA:

		ret = -ENXIO;

		if (!sclp.has_cmma)

			break;

		ret = -EINVAL;

		ret = -EINVAL;

		if (!kvm->arch.use_cmma)

		if (!kvm->arch.use_cmma)

			break;

			break;
@@ -964,6 +967,8 @@ static int kvm_s390_vm_has_attr(struct kvm *kvm, struct kvm_device_attr *attr) 
		switch (attr->attr) {

		switch (attr->attr) {

		case KVM_S390_VM_MEM_ENABLE_CMMA:

		case KVM_S390_VM_MEM_ENABLE_CMMA:

		case KVM_S390_VM_MEM_CLR_CMMA:

		case KVM_S390_VM_MEM_CLR_CMMA:

			ret = sclp.has_cmma ? 0 : -ENXIO;

			break;

		case KVM_S390_VM_MEM_LIMIT_SIZE:

		case KVM_S390_VM_MEM_LIMIT_SIZE:

			ret = 0;

			ret = 0;

			break;

			break;