KVM: s390: resetting the Topology-Change-Report

During a subsystem reset the Topology-Change-Report is cleared.

Let's give userland the possibility to clear the MTCR in the case
of a subsystem reset.

To migrate the MTCR, we give userland the possibility to
query the MTCR state.

We indicate KVM support for the CPU topology facility with a new
KVM capability: KVM_CAP_S390_CPU_TOPOLOGY.

Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
Reviewed-by: Janis Schoetterl-Glausch <scgl@linux.ibm.com>
Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
Message-Id: <20220714194334.127812-1-pmorel@linux.ibm.com>
Link: https://lore.kernel.org/all/20220714194334.127812-1-pmorel@linux.ibm.com/
[frankja@linux.ibm.com: Simple conflict resolution in Documentation/virt/kvm/api.rst]
Signed-off-by: Janosch Frank <frankja@linux.ibm.com>

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 5be5cc5..3c4551a 100644 (file)
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -8269,6 +8269,31 @@ The capability has no effect if the nx_huge_pages module parameter is not set.
 
 This capability may only be set before any vCPUs are created.
 
+8.39 KVM_CAP_S390_CPU_TOPOLOGY
+------------------------------
+
+:Capability: KVM_CAP_S390_CPU_TOPOLOGY
+:Architectures: s390
+:Type: vm
+
+This capability indicates that KVM will provide the S390 CPU Topology
+facility which consist of the interpretation of the PTF instruction for
+the function code 2 along with interception and forwarding of both the
+PTF instruction with function codes 0 or 1 and the STSI(15,1,x)
+instruction to the userland hypervisor.
+
+The stfle facility 11, CPU Topology facility, should not be indicated
+to the guest without this capability.
+
+When this capability is present, KVM provides a new attribute group
+on vm fd, KVM_S390_VM_CPU_TOPOLOGY.
+This new attribute allows to get, set or clear the Modified Change
+Topology Report (MTCR) bit of the SCA through the kvm_device_attr
+structure.
+
+When getting the Modified Change Topology Report value, the attr->addr
+must point to a byte where the value will be stored or retrieved from.
+
 9. Known KVM API problems
 =========================
 

diff --git a/arch/s390/include/uapi/asm/kvm.h b/arch/s390/include/uapi/asm/kvm.h
index 7a6b148..a73cf01 100644 (file)
--- a/arch/s390/include/uapi/asm/kvm.h
+++ b/arch/s390/include/uapi/asm/kvm.h
@@ -74,6 +74,7 @@ struct kvm_s390_io_adapter_req {
 #define KVM_S390_VM_CRYPTO             2
 #define KVM_S390_VM_CPU_MODEL          3
 #define KVM_S390_VM_MIGRATION          4
+#define KVM_S390_VM_CPU_TOPOLOGY       5
 
 /* kvm attributes for mem_ctrl */
 #define KVM_S390_VM_MEM_ENABLE_CMMA    0

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 5d18b66..edfd4bb 100644 (file)
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -642,6 +642,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
        case KVM_CAP_S390_ZPCI_OP:
                r = kvm_s390_pci_interp_allowed();
                break;
+       case KVM_CAP_S390_CPU_TOPOLOGY:
+               r = test_facility(11);
+               break;
        default:
                r = 0;
        }
@@ -853,6 +856,20 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm, struct kvm_enable_cap *cap)
                icpt_operexc_on_all_vcpus(kvm);
                r = 0;
                break;
+       case KVM_CAP_S390_CPU_TOPOLOGY:
+               r = -EINVAL;
+               mutex_lock(&kvm->lock);
+               if (kvm->created_vcpus) {
+                       r = -EBUSY;
+               } else if (test_facility(11)) {
+                       set_kvm_facility(kvm->arch.model.fac_mask, 11);
+                       set_kvm_facility(kvm->arch.model.fac_list, 11);
+                       r = 0;
+               }
+               mutex_unlock(&kvm->lock);
+               VM_EVENT(kvm, 3, "ENABLE: CAP_S390_CPU_TOPOLOGY %s",
+                        r ? "(not available)" : "(success)");
+               break;
        default:
                r = -EINVAL;
                break;
@@ -1789,6 +1806,31 @@ static void kvm_s390_update_topology_change_report(struct kvm *kvm, bool val)
        read_unlock(&kvm->arch.sca_lock);
 }
 
+static int kvm_s390_set_topo_change_indication(struct kvm *kvm,
+                                              struct kvm_device_attr *attr)
+{
+       if (!test_kvm_facility(kvm, 11))
+               return -ENXIO;
+
+       kvm_s390_update_topology_change_report(kvm, !!attr->attr);
+       return 0;
+}
+
+static int kvm_s390_get_topo_change_indication(struct kvm *kvm,
+                                              struct kvm_device_attr *attr)
+{
+       u8 topo;
+
+       if (!test_kvm_facility(kvm, 11))
+               return -ENXIO;
+
+       read_lock(&kvm->arch.sca_lock);
+       topo = ((struct bsca_block *)kvm->arch.sca)->utility.mtcr;
+       read_unlock(&kvm->arch.sca_lock);
+
+       return put_user(topo, (u8 __user *)attr->addr);
+}
+
 static int kvm_s390_vm_set_attr(struct kvm *kvm, struct kvm_device_attr *attr)
 {
        int ret;
@@ -1809,6 +1851,9 @@ static int kvm_s390_vm_set_attr(struct kvm *kvm, struct kvm_device_attr *attr)
        case KVM_S390_VM_MIGRATION:
                ret = kvm_s390_vm_set_migration(kvm, attr);
                break;
+       case KVM_S390_VM_CPU_TOPOLOGY:
+               ret = kvm_s390_set_topo_change_indication(kvm, attr);
+               break;
        default:
                ret = -ENXIO;
                break;
@@ -1834,6 +1879,9 @@ static int kvm_s390_vm_get_attr(struct kvm *kvm, struct kvm_device_attr *attr)
        case KVM_S390_VM_MIGRATION:
                ret = kvm_s390_vm_get_migration(kvm, attr);
                break;
+       case KVM_S390_VM_CPU_TOPOLOGY:
+               ret = kvm_s390_get_topo_change_indication(kvm, attr);
+               break;
        default:
                ret = -ENXIO;
                break;
@@ -1907,6 +1955,9 @@ static int kvm_s390_vm_has_attr(struct kvm *kvm, struct kvm_device_attr *attr)
        case KVM_S390_VM_MIGRATION:
                ret = 0;
                break;
+       case KVM_S390_VM_CPU_TOPOLOGY:
+               ret = test_kvm_facility(kvm, 11) ? 0 : -ENXIO;
+               break;
        default:
                ret = -ENXIO;
                break;

diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 20817dd..7e06194 100644 (file)
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1168,6 +1168,7 @@ struct kvm_ppc_resize_hpt {
 #define KVM_CAP_X86_NOTIFY_VMEXIT 219
 #define KVM_CAP_VM_DISABLE_NX_HUGE_PAGES 220
 #define KVM_CAP_S390_ZPCI_OP 221
+#define KVM_CAP_S390_CPU_TOPOLOGY 222
 
 #ifdef KVM_CAP_IRQ_ROUTING