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: Dominik Dingel <dingel@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

diff --git a/Documentation/virtual/kvm/devices/vm.txt b/Documentation/virtual/kvm/devices/vm.txt
index 562bee6e600b916419b18e4b6bc2fb8f4f96922a..0d16f96c0eac9672a540498bbefe773dc55f03a0 100644 (file)
--- a/Documentation/virtual/kvm/devices/vm.txt
+++ b/Documentation/virtual/kvm/devices/vm.txt
@@ -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.

diff --git a/arch/s390/include/uapi/asm/kvm.h b/arch/s390/include/uapi/asm/kvm.h
index c003c6a73b1e3e883b814aff03704a43c3c0d9a4..e35c79821d29dbb5d368c1c952b27fe15bc31402 100644 (file)
--- a/arch/s390/include/uapi/asm/kvm.h
+++ b/arch/s390/include/uapi/asm/kvm.h
@@ -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 */

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index fc2fe49488c0fc61425847507288e976b1254921..fe2396cc0856232d9334baf4a46f90df2b6e892b 100644 (file)
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -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;