Re: [PULL 06/25] s390x/cpu topology: resetting the Topology-Change-Report

[Stefan Hajnoczi]

On Wed, 18 Oct 2023 at 06:09, Thomas Huth <thuth@redhat.com> wrote:
>
> From: Pierre Morel <pmorel@linux.ibm.com>
>
> 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: Thomas Huth <thuth@redhat.com>
> Reviewed-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
> Co-developed-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
> Signed-off-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
> Message-ID: <20231016183925.2384704-7-nsg@linux.ibm.com>
> Signed-off-by: Thomas Huth <thuth@redhat.com>
> ---
>  include/hw/s390x/cpu-topology.h |  1 +
>  target/s390x/cpu.h              |  1 +
>  target/s390x/kvm/kvm_s390x.h    |  1 +
>  hw/s390x/cpu-topology.c         | 11 +++++++++++
>  hw/s390x/s390-virtio-ccw.c      |  3 +++
>  target/s390x/cpu-sysemu.c       | 13 +++++++++++++
>  target/s390x/kvm/kvm.c          | 17 +++++++++++++++++
>  7 files changed, 47 insertions(+)
>
> diff --git a/include/hw/s390x/cpu-topology.h b/include/hw/s390x/cpu-topology.h
> index f95d26d37c..e33e7c66df 100644
> --- a/include/hw/s390x/cpu-topology.h
> +++ b/include/hw/s390x/cpu-topology.h
> @@ -56,6 +56,7 @@ static inline void s390_topology_setup_cpu(MachineState *ms,
>  #endif
>
>  extern S390Topology s390_topology;
> +void s390_topology_reset(void);

Please take a look at the following CI failure:

/usr/bin/ld: libqemu-s390x-softmmu.fa.p/hw_s390x_s390-virtio-ccw.c.o:
in function `subsystem_reset':
/home/gitlab-runner/builds/E8PpwMky/0/qemu-project/qemu/build/../hw/s390x/s390-virtio-ccw.c:128:
undefined reference to `s390_topology_reset'

https://gitlab.com/qemu-project/qemu/-/jobs/5330218593

>
>  static inline int s390_std_socket(int n, CpuTopology *smp)
>  {
> diff --git a/target/s390x/cpu.h b/target/s390x/cpu.h
> index 09bff39fe4..40c5cedd0e 100644
> --- a/target/s390x/cpu.h
> +++ b/target/s390x/cpu.h
> @@ -654,6 +654,7 @@ typedef struct SysIBCPUListEntry {
>  QEMU_BUILD_BUG_ON(sizeof(SysIBCPUListEntry) != 16);
>
>  void insert_stsi_15_1_x(S390CPU *cpu, int sel2, uint64_t addr, uint8_t ar, 
> uintptr_t ra);
> +void s390_cpu_topology_set_changed(bool changed);
>
>  /* MMU defines */
>  #define ASCE_ORIGIN           (~0xfffULL) /* segment table origin            
>  */
> diff --git a/target/s390x/kvm/kvm_s390x.h b/target/s390x/kvm/kvm_s390x.h
> index f9785564d0..649dae5948 100644
> --- a/target/s390x/kvm/kvm_s390x.h
> +++ b/target/s390x/kvm/kvm_s390x.h
> @@ -47,5 +47,6 @@ 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 13168341b6..7ec9319272 100644
> --- a/hw/s390x/cpu-topology.c
> +++ b/hw/s390x/cpu-topology.c
> @@ -90,6 +90,17 @@ static void s390_topology_init(MachineState *ms)
>                                              smp->books * smp->drawers);
>  }
>
> +/**
> + * s390_topology_reset:
> + *
> + * Generic reset for CPU topology, calls s390_topology_reset()
> + * to reset the kernel Modified Topology Change Record.
> + */
> +void s390_topology_reset(void)
> +{
> +    s390_cpu_topology_set_changed(false);
> +}
> +
>  /**
>   * s390_topology_cpu_default:
>   * @cpu: pointer to a S390CPU
> diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
> index 7fe2bce20c..6012165d41 100644
> --- a/hw/s390x/s390-virtio-ccw.c
> +++ b/hw/s390x/s390-virtio-ccw.c
> @@ -124,6 +124,9 @@ static void subsystem_reset(void)
>              device_cold_reset(dev);
>          }
>      }
> +    if (s390_has_topology()) {
> +        s390_topology_reset();
> +    }
>  }
>
>  static int virtio_ccw_hcall_notify(const uint64_t *args)
> diff --git a/target/s390x/cpu-sysemu.c b/target/s390x/cpu-sysemu.c
> index 8112561e5e..1cd30c1d84 100644
> --- a/target/s390x/cpu-sysemu.c
> +++ b/target/s390x/cpu-sysemu.c
> @@ -307,3 +307,16 @@ 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_set_changed(bool changed)
> +{
> +    int ret;
> +
> +    if (kvm_enabled()) {
> +        ret = kvm_s390_topology_set_mtcr(changed);
> +        if (ret) {
> +            error_report("Failed to set Modified Topology Change Report: %s",
> +                         strerror(-ret));
> +        }
> +    }
> +}
> diff --git a/target/s390x/kvm/kvm.c b/target/s390x/kvm/kvm.c
> index 53d6300809..d6bda3a2a8 100644
> --- a/target/s390x/kvm/kvm.c
> +++ b/target/s390x/kvm/kvm.c
> @@ -2664,6 +2664,23 @@ 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,
> +    };
> +
> +    if (!s390_has_feat(S390_FEAT_CONFIGURATION_TOPOLOGY)) {
> +        return 0;
> +    }
> +    if (!kvm_vm_check_attr(kvm_state, KVM_S390_VM_CPU_TOPOLOGY, attr)) {
> +        return -ENOTSUP;
> +    }
> +
> +    return kvm_vm_ioctl(kvm_state, KVM_SET_DEVICE_ATTR, &attribute);
> +}
> +
>  void kvm_arch_accel_class_init(ObjectClass *oc)
>  {
>  }
> --
> 2.41.0
>
>