Re: [PATCH v10 3/9] s390x/cpu_topology: resetting the Topology-Change-Report

[Pierre Morel]

On 10/27/22 11:58, Cédric Le Goater wrote:

On 10/27/22 11:11, Pierre Morel wrote:

On 10/27/22 10:14, Thomas Huth wrote:

On 12/10/2022 18.21, Pierre Morel wrote:

During a subsystem reset the Topology-Change-Report is cleared
by the machine.
Let's ask KVM to clear the Modified Topology Change Report (MTCR)
  bit of the SCA in the case of a subsystem reset.

Signed-off-by: Pierre Morel <pmo...@linux.ibm.com>
Reviewed-by: Nico Boehr <n...@linux.ibm.com>
Reviewed-by: Janis Schoetterl-Glausch <s...@linux.ibm.com>
---
  target/s390x/cpu.h           |  1 +
  target/s390x/kvm/kvm_s390x.h |  1 +
  hw/s390x/cpu-topology.c      | 12 ++++++++++++
  hw/s390x/s390-virtio-ccw.c   |  1 +
  target/s390x/cpu-sysemu.c    |  7 +++++++
  target/s390x/kvm/kvm.c       | 23 +++++++++++++++++++++++
  6 files changed, 45 insertions(+)

diff --git a/target/s390x/cpu.h b/target/s390x/cpu.h
index d604aa9c78..9b35795ac8 100644
--- a/target/s390x/cpu.h
+++ b/target/s390x/cpu.h
@@ -825,6 +825,7 @@ void s390_enable_css_support(S390CPU *cpu);
  void s390_do_cpu_set_diag318(CPUState *cs, run_on_cpu_data arg);

  int s390_assign_subch_ioeventfd(EventNotifier *notifier, uint32_t sch_id,

                                  int vq, bool assign);
+void s390_cpu_topology_reset(void);
  #ifndef CONFIG_USER_ONLY
  unsigned int s390_cpu_set_state(uint8_t cpu_state, S390CPU *cpu);
  #else

diff --git a/target/s390x/kvm/kvm_s390x.h b/target/s390x/kvm/kvm_s390x.h

index aaae8570de..a13c8fb9a3 100644
--- a/target/s390x/kvm/kvm_s390x.h
+++ b/target/s390x/kvm/kvm_s390x.h
@@ -46,5 +46,6 @@ void kvm_s390_crypto_reset(void);
  void kvm_s390_restart_interrupt(S390CPU *cpu);
  void kvm_s390_stop_interrupt(S390CPU *cpu);
  void kvm_s390_set_diag318(CPUState *cs, uint64_t diag318_info);
+int kvm_s390_topology_set_mtcr(uint64_t attr);
  #endif /* KVM_S390X_H */
diff --git a/hw/s390x/cpu-topology.c b/hw/s390x/cpu-topology.c
index c73cebfe6f..9f202621d0 100644
--- a/hw/s390x/cpu-topology.c
+++ b/hw/s390x/cpu-topology.c

@@ -107,6 +107,17 @@ static void s390_topology_realize(DeviceState *dev, Error **errp)

      qemu_mutex_init(&topo->topo_mutex);
  }
+/**
+ * s390_topology_reset:
+ * @dev: the device
+ *
+ * Calls the sysemu topology reset
+ */
+static void s390_topology_reset(DeviceState *dev)
+{
+    s390_cpu_topology_reset();
+}
+
  /**
   * topology_class_init:
   * @oc: Object class

@@ -120,6 +131,7 @@ static void topology_class_init(ObjectClass *oc, void *data)

      dc->realize = s390_topology_realize;
      set_bit(DEVICE_CATEGORY_MISC, dc->categories);
+    dc->reset = s390_topology_reset;
  }
  static const TypeInfo cpu_topology_info = {
diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
index aa99a62e42..362378454a 100644
--- a/hw/s390x/s390-virtio-ccw.c
+++ b/hw/s390x/s390-virtio-ccw.c
@@ -113,6 +113,7 @@ static const char *const reset_dev_types[] = {
      "s390-flic",
      "diag288",
      TYPE_S390_PCI_HOST_BRIDGE,
+    TYPE_S390_CPU_TOPOLOGY,
  };
  static void subsystem_reset(void)
diff --git a/target/s390x/cpu-sysemu.c b/target/s390x/cpu-sysemu.c
index 948e4bd3e0..707c0b658c 100644
--- a/target/s390x/cpu-sysemu.c
+++ b/target/s390x/cpu-sysemu.c

@@ -306,3 +306,10 @@ void s390_do_cpu_set_diag318(CPUState *cs, run_on_cpu_data arg)

          kvm_s390_set_diag318(cs, arg.host_ulong);
      }
  }
+
+void s390_cpu_topology_reset(void)
+{
+    if (kvm_enabled()) {
+        kvm_s390_topology_set_mtcr(0);
+    }
+}
diff --git a/target/s390x/kvm/kvm.c b/target/s390x/kvm/kvm.c
index f96630440b..9c994d27d5 100644
--- a/target/s390x/kvm/kvm.c
+++ b/target/s390x/kvm/kvm.c
@@ -2585,3 +2585,26 @@ int kvm_s390_get_zpci_op(void)
  {
      return cap_zpci_op;
  }
+
+int kvm_s390_topology_set_mtcr(uint64_t attr)
+{
+    struct kvm_device_attr attribute = {
+        .group = KVM_S390_VM_CPU_TOPOLOGY,
+        .attr  = attr,
+    };
+    int ret;
+
+    if (!s390_has_feat(S390_FEAT_CONFIGURATION_TOPOLOGY)) {
+        return -EFAULT;

EFAULT is something that indicates a bad address (e.g. a segmentation fault) ... so this definitely sounds like a bad choice for an error code here.

Hum, yes, ENODEV seems besser no?

-ENOTSUP would be 'meilleur' may be ?  :)

yes better :)

thanks,
Pierre

--
Pierre Morel
IBM Lab Boeblingen