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From:   Pierre Morel <pmorel@linux.ibm.com>
To:     kvm@vger.kernel.org
Cc:     linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org,
        borntraeger@de.ibm.com, frankja@linux.ibm.com, cohuck@redhat.com,
        david@redhat.com, thuth@redhat.com, imbrenda@linux.ibm.com,
        hca@linux.ibm.com, gor@linux.ibm.com, pmorel@linux.ibm.com,
        wintera@linux.ibm.com, seiden@linux.ibm.com, nrb@linux.ibm.com,
        scgl@linux.ibm.com
Subject: [PATCH v12 3/3] KVM: s390: resetting the Topology-Change-Report
Date:   Mon, 11 Jul 2022 10:41:48 +0200
Message-Id: <20220711084148.25017-4-pmorel@linux.ibm.com>
In-Reply-To: <20220711084148.25017-1-pmorel@linux.ibm.com>
References: <20220711084148.25017-1-pmorel@linux.ibm.com>
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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>
---
 Documentation/virt/kvm/api.rst   | 25 ++++++++++++++
 arch/s390/include/uapi/asm/kvm.h |  1 +
 arch/s390/kvm/kvm-s390.c         | 56 ++++++++++++++++++++++++++++++++
 include/uapi/linux/kvm.h         |  1 +
 4 files changed, 83 insertions(+)

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 11e00a46c610..5e086125d8ad 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -7956,6 +7956,31 @@ should adjust CPUID leaf 0xA to reflect that the PMU is disabled.
 When enabled, KVM will exit to userspace with KVM_EXIT_SYSTEM_EVENT of
 type KVM_SYSTEM_EVENT_SUSPEND to process the guest suspend request.
 
+8.37 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.
+
 9. Known KVM API problems
 =========================
 
diff --git a/arch/s390/include/uapi/asm/kvm.h b/arch/s390/include/uapi/asm/kvm.h
index 7a6b14874d65..a73cf01a1606 100644
--- 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 70436bfff53a..b18e0b940b26 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -606,6 +606,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 	case KVM_CAP_S390_PROTECTED:
 		r = is_prot_virt_host();
 		break;
+	case KVM_CAP_S390_CPU_TOPOLOGY:
+		r = test_facility(11);
+		break;
 	default:
 		r = 0;
 	}
@@ -817,6 +820,20 @@ 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;
@@ -1717,6 +1734,36 @@ static void kvm_s390_update_topology_change_report(struct kvm *kvm, bool val)
 	read_unlock(&kvm->arch.sca_lock);
 }
 
+static int kvm_s390_set_topology(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_topology(struct kvm *kvm, struct kvm_device_attr *attr)
+{
+	union sca_utility utility;
+	struct bsca_block *sca;
+	__u8 topo;
+
+	if (!test_kvm_facility(kvm, 11))
+		return -ENXIO;
+
+	read_lock(&kvm->arch.sca_lock);
+	sca = kvm->arch.sca;
+	utility.val = READ_ONCE(sca->utility.val);
+	read_unlock(&kvm->arch.sca_lock);
+	topo = utility.mtcr;
+
+	if (copy_to_user((void __user *)attr->addr, &topo, sizeof(topo)))
+		return -EFAULT;
+
+	return 0;
+}
+
 static int kvm_s390_vm_set_attr(struct kvm *kvm, struct kvm_device_attr *attr)
 {
 	int ret;
@@ -1737,6 +1784,9 @@ 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_topology(kvm, attr);
+		break;
 	default:
 		ret = -ENXIO;
 		break;
@@ -1762,6 +1812,9 @@ 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_topology(kvm, attr);
+		break;
 	default:
 		ret = -ENXIO;
 		break;
@@ -1835,6 +1888,9 @@ 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 5088bd9f1922..33317d820032 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1157,6 +1157,7 @@ struct kvm_ppc_resize_hpt {
 #define KVM_CAP_VM_TSC_CONTROL 214
 #define KVM_CAP_SYSTEM_EVENT_DATA 215
 #define KVM_CAP_ARM_SYSTEM_SUSPEND 216
+#define KVM_CAP_S390_CPU_TOPOLOGY 217
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
-- 
2.31.1