[PATCH v8 2/2] s390x: KVM: resetting the Topology-Change-Report

[Pierre Morel <pmorel@linux.ibm.com>]

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, let's give userland the possibility to
query the MTCR state.

Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
---
 arch/s390/include/uapi/asm/kvm.h |   9 +++
 arch/s390/kvm/kvm-s390.c         | 103 +++++++++++++++++++++++++++++++
 2 files changed, 112 insertions(+)

diff --git a/arch/s390/include/uapi/asm/kvm.h b/arch/s390/include/uapi/asm/kvm.h
index 7a6b14874d65..bb3df6d49f27 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
@@ -171,6 +172,14 @@ struct kvm_s390_vm_cpu_subfunc {
 #define KVM_S390_VM_MIGRATION_START	1
 #define KVM_S390_VM_MIGRATION_STATUS	2
 
+/* kvm attributes for cpu topology */
+#define KVM_S390_VM_CPU_TOPO_MTR_CLEAR	0
+#define KVM_S390_VM_CPU_TOPO_MTR_SET	1
+
+struct kvm_s390_cpu_topology {
+	__u16 mtcr;
+};
+
 /* 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 925ccc59f283..755f325c9e70 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -1756,6 +1756,100 @@ static int kvm_s390_sca_set_mtcr(struct kvm *kvm)
 	return 0;
 }
 
+/**
+ * kvm_s390_sca_clear_mtcr
+ * @kvm: guest KVM description
+ *
+ * Is only relevant if the topology facility is present,
+ * the caller should check KVM facility 11
+ *
+ * Updates the Multiprocessor Topology-Change-Report to signal
+ * the guest with a topology change.
+ */
+static int kvm_s390_sca_clear_mtcr(struct kvm *kvm)
+{
+	struct bsca_block *sca = kvm->arch.sca;
+	struct kvm_vcpu *vcpu;
+	int val;
+
+	vcpu = kvm_s390_get_first_vcpu(kvm);
+	if (!vcpu)
+		return -ENODEV;
+
+	ipte_lock(vcpu);
+	val = READ_ONCE(sca->utility);
+	WRITE_ONCE(sca->utility, sca->utility & ~SCA_UTILITY_MTCR);
+	ipte_unlock(vcpu);
+
+	return 0;
+}
+
+/**
+ * kvm_s390_sca_get_mtcr
+ * @kvm: guest KVM description
+ *
+ * Is only relevant if the topology facility is present,
+ * the caller should check KVM facility 11
+ *
+ * reports to QEMU the Multiprocessor Topology-Change-Report.
+ */
+static int kvm_s390_sca_get_mtcr(struct kvm *kvm)
+{
+	struct bsca_block *sca = kvm->arch.sca;
+	struct kvm_vcpu *vcpu;
+	int val;
+
+	vcpu = kvm_s390_get_first_vcpu(kvm);
+	if (!vcpu)
+		return -ENODEV;
+
+	ipte_lock(vcpu);
+	val = READ_ONCE(sca->utility);
+	ipte_unlock(vcpu);
+
+	return val;
+}
+
+static int kvm_s390_set_topology(struct kvm *kvm, struct kvm_device_attr *attr)
+{
+	int ret = -EFAULT;
+
+	if (!test_kvm_facility(kvm, 11))
+		return -ENXIO;
+
+	switch (attr->attr) {
+	case KVM_S390_VM_CPU_TOPO_MTR_SET:
+		ret = kvm_s390_sca_set_mtcr(kvm);
+		break;
+	case KVM_S390_VM_CPU_TOPO_MTR_CLEAR:
+		ret = kvm_s390_sca_clear_mtcr(kvm);
+		break;
+	}
+
+	return ret;
+}
+
+static int kvm_s390_get_topology(struct kvm *kvm, struct kvm_device_attr *attr)
+{
+	struct kvm_s390_cpu_topology *topology;
+	int ret = 0;
+
+	if (!test_kvm_facility(kvm, 11))
+		return -ENXIO;
+
+	topology = kzalloc(sizeof(*topology), GFP_KERNEL);
+	if (!topology)
+		return -ENOMEM;
+
+	topology->mtcr =  kvm_s390_sca_get_mtcr(kvm);
+	if (copy_to_user((void __user *)attr->addr, topology,
+			 sizeof(struct kvm_s390_cpu_topology)))
+		ret = -EFAULT;
+
+	kfree(topology);
+	return ret;
+}
+
 static int kvm_s390_vm_set_attr(struct kvm *kvm, struct kvm_device_attr *attr)
 {
 	int ret;
@@ -1776,6 +1870,9 @@ 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;
@@ -1801,6 +1898,9 @@ 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;
@@ -1874,6 +1974,9 @@ 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;
-- 
2.27.0