linux-kernel - [PATCH v9 3/3] s390x: KVM: resetting the Topology-Change-Report

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Message-Id: <20220506092403.47406-4-pmorel@linux.ibm.com>
Date:   Fri,  6 May 2022 11:24:03 +0200
From:   Pierre Morel <pmorel@...ux.ibm.com>
To:     kvm@...r.kernel.org
Cc:     linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        borntraeger@...ibm.com, frankja@...ux.ibm.com, cohuck@...hat.com,
        david@...hat.com, thuth@...hat.com, imbrenda@...ux.ibm.com,
        hca@...ux.ibm.com, gor@...ux.ibm.com, pmorel@...ux.ibm.com,
        wintera@...ux.ibm.com, seiden@...ux.ibm.com, nrb@...ux.ibm.com
Subject: [PATCH v9 3/3] s390x: KVM: 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, let's give userland the possibility to
query the MTCR state.

Signed-off-by: Pierre Morel <pmorel@...ux.ibm.com>
---
 arch/s390/include/uapi/asm/kvm.h |  5 ++
 arch/s390/kvm/kvm-s390.c         | 79 ++++++++++++++++++++++++++++++++
 2 files changed, 84 insertions(+)

diff --git a/arch/s390/include/uapi/asm/kvm.h b/arch/s390/include/uapi/asm/kvm.h
index 7a6b14874d65..abdcf4069343 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 +172,10 @@ 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
+
 /* 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 c8bdce31464f..80a1244f0ead 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -1731,6 +1731,76 @@ static void kvm_s390_sca_set_mtcr(struct kvm *kvm)
 	ipte_unlock(kvm);
 }
 
+/**
+ * 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 void kvm_s390_sca_clear_mtcr(struct kvm *kvm)
+{
+	struct bsca_block *sca = kvm->arch.sca; /* SCA version doesn't matter */
+
+	ipte_lock(kvm);
+	sca->utility  &= ~SCA_UTILITY_MTCR;
+	ipte_unlock(kvm);
+}
+
+static int kvm_s390_set_topology(struct kvm *kvm, struct kvm_device_attr *attr)
+{
+	if (!test_kvm_facility(kvm, 11))
+		return -ENXIO;
+
+	switch (attr->attr) {
+	case KVM_S390_VM_CPU_TOPO_MTR_SET:
+		kvm_s390_sca_set_mtcr(kvm);
+		break;
+	case KVM_S390_VM_CPU_TOPO_MTR_CLEAR:
+		kvm_s390_sca_clear_mtcr(kvm);
+		break;
+	}
+	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; /* SCA version doesn't matter */
+	int val;
+
+	ipte_lock(kvm);
+	val = !!(sca->utility & SCA_UTILITY_MTCR);
+	ipte_unlock(kvm);
+
+	return val;
+}
+
+static int kvm_s390_get_topology(struct kvm *kvm, struct kvm_device_attr *attr)
+{
+	int mtcr;
+
+	if (!test_kvm_facility(kvm, 11))
+		return -ENXIO;
+
+	mtcr = kvm_s390_sca_get_mtcr(kvm);
+	if (copy_to_user((void __user *)attr->addr, &mtcr, sizeof(mtcr)))
+		return -EFAULT;
+
+	return 0;
+}
+
 static int kvm_s390_vm_set_attr(struct kvm *kvm, struct kvm_device_attr *attr)
 {
 	int ret;
@@ -1751,6 +1821,9 @@ 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;
@@ -1776,6 +1849,9 @@ 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;
@@ -1849,6 +1925,9 @@ 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