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

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

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 <pmorel@linux.ibm.com>
>> Reviewed-by: Nico Boehr <nrb@linux.ibm.com>
>> Reviewed-by: Janis Schoetterl-Glausch <scgl@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?

> 
>   Thomas
> 
> 

-- 
Pierre Morel
IBM Lab Boeblingen