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Commit 4f718eab authored by Dominik Dingel's avatar Dominik Dingel Committed by Christian Borntraeger
Browse files

KVM: s390: Exploiting generic userspace interface for cmma 



To enable CMMA and to reset its state we use the vm kvm_device ioctls,
encapsulating attributes within the KVM_S390_VM_MEM_CTRL group.

Signed-off-by: default avatarDominik Dingel <dingel@linux.vnet.ibm.com>
Signed-off-by: default avatarChristian Borntraeger <borntraeger@de.ibm.com>
parent b31605c1

Documentation/virtual/kvm/devices/vm.txt

+16 −0
Original line number Diff line number Diff line
@@ -8,3 +8,19 @@ and controls. 


The groups and attributes per virtual machine, if any, are architecture

specific.



1. GROUP: KVM_S390_VM_MEM_CTRL

Architectures: s390



1.1. ATTRIBUTE: KVM_S390_VM_MEM_CTRL

Parameters: none

Returns: -EBUSY if already a vcpus is defined, otherwise 0



Enables CMMA for the virtual machine



1.2. ATTRIBUTE: KVM_S390_VM_CLR_CMMA

Parameteres: none

Returns: 0



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.

arch/s390/include/uapi/asm/kvm.h

+7 −0
Original line number Diff line number Diff line
@@ -54,6 +54,13 @@ struct kvm_s390_io_adapter_req { 
	__u64 addr;

};



/* kvm attr_group  on vm fd */

#define KVM_S390_VM_MEM_CTRL		0



/* kvm attributes for mem_ctrl */

#define KVM_S390_VM_MEM_ENABLE_CMMA	0

#define KVM_S390_VM_MEM_CLR_CMMA	1



/* for KVM_GET_REGS and KVM_SET_REGS */

struct kvm_regs {

	/* general purpose regs for s390 */

arch/s390/kvm/kvm-s390.c

+43 −0
Original line number Diff line number Diff line
@@ -258,11 +258,43 @@ static int kvm_vm_ioctl_enable_cap(struct kvm *kvm, struct kvm_enable_cap *cap) 
	return r;

}



static int kvm_s390_mem_control(struct kvm *kvm, struct kvm_device_attr *attr)

{

	int ret;

	unsigned int idx;

	switch (attr->attr) {

	case KVM_S390_VM_MEM_ENABLE_CMMA:

		ret = -EBUSY;

		mutex_lock(&kvm->lock);

		if (atomic_read(&kvm->online_vcpus) == 0) {

			kvm->arch.use_cmma = 1;

			ret = 0;

		}

		mutex_unlock(&kvm->lock);

		break;

	case KVM_S390_VM_MEM_CLR_CMMA:

		mutex_lock(&kvm->lock);

		idx = srcu_read_lock(&kvm->srcu);

		page_table_reset_pgste(kvm->arch.gmap->mm, 0, TASK_SIZE, false);

		srcu_read_unlock(&kvm->srcu, idx);

		mutex_unlock(&kvm->lock);

		ret = 0;

		break;

	default:

		ret = -ENXIO;

		break;

	}

	return ret;

}



static int kvm_s390_vm_set_attr(struct kvm *kvm, struct kvm_device_attr *attr)

{

	int ret;



	switch (attr->group) {

	case KVM_S390_VM_MEM_CTRL:

		ret = kvm_s390_mem_control(kvm, attr);

		break;

	default:

		ret = -ENXIO;

		break;
@@ -281,6 +313,17 @@ static int kvm_s390_vm_has_attr(struct kvm *kvm, struct kvm_device_attr *attr) 
	int ret;



	switch (attr->group) {

	case KVM_S390_VM_MEM_CTRL:

		switch (attr->attr) {

		case KVM_S390_VM_MEM_ENABLE_CMMA:

		case KVM_S390_VM_MEM_CLR_CMMA:

			ret = 0;

			break;

		default:

			ret = -ENXIO;

			break;

		}

		break;

	default:

		ret = -ENXIO;

		break;