Re: [PATCH v20 06/21] s390x/cpu topology: interception of PTF instruction

[Nina Schoetterl-Glausch <nsg@linux.ibm.com>]

On Tue, 2023-04-25 at 18:14 +0200, Pierre Morel wrote:
> When the host supports the CPU topology facility, the PTF
> instruction with function code 2 is interpreted by the SIE,
> provided that the userland hypervisor activates the interpretation
> by using the KVM_CAP_S390_CPU_TOPOLOGY KVM extension.
> 
> The PTF instructions with function code 0 and 1 are intercepted
> and must be emulated by the userland hypervisor.
> 
> During RESET all CPU of the configuration are placed in
> horizontal polarity.
> 
> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>

Reviewed-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>

See nit below.
> ---
>  include/hw/s390x/s390-virtio-ccw.h |  6 ++++
>  hw/s390x/cpu-topology.c            | 51 ++++++++++++++++++++++++++++++
>  target/s390x/kvm/kvm.c             | 11 +++++++
>  3 files changed, 68 insertions(+)
> 
> diff --git a/include/hw/s390x/s390-virtio-ccw.h b/include/hw/s390x/s390-virtio-ccw.h
> index 9bba21a916..c1d46e78af 100644
> --- a/include/hw/s390x/s390-virtio-ccw.h
> +++ b/include/hw/s390x/s390-virtio-ccw.h
> @@ -30,6 +30,12 @@ struct S390CcwMachineState {
>      uint8_t loadparm[8];
>  };
>  
> +#define S390_PTF_REASON_NONE (0x00 << 8)
> +#define S390_PTF_REASON_DONE (0x01 << 8)
> +#define S390_PTF_REASON_BUSY (0x02 << 8)
> +#define S390_TOPO_FC_MASK 0xffUL
> +void s390_handle_ptf(S390CPU *cpu, uint8_t r1, uintptr_t ra);
> +
>  struct S390CcwMachineClass {
>      /*< private >*/
>      MachineClass parent_class;
> diff --git a/hw/s390x/cpu-topology.c b/hw/s390x/cpu-topology.c
> index c98439ff7a..3c7bbff4bc 100644
> --- a/hw/s390x/cpu-topology.c
> +++ b/hw/s390x/cpu-topology.c
> @@ -96,6 +96,56 @@ static void s390_topology_init(MachineState *ms)
>      QTAILQ_INSERT_HEAD(&s390_topology.list, entry, next);
>  }
>  
> +/*
> + * s390_handle_ptf:
> + *
> + * @register 1: contains the function code
> + *
> + * Function codes 0 (horizontal) and 1 (vertical) define the CPU
> + * polarization requested by the guest.
> + *
> + * Function code 2 is handling topology changes and is interpreted
> + * by the SIE.
> + */
> +void s390_handle_ptf(S390CPU *cpu, uint8_t r1, uintptr_t ra)
> +{
> +    CPUS390XState *env = &cpu->env;
> +    uint64_t reg = env->regs[r1];
> +    int fc = reg & S390_TOPO_FC_MASK;
> +
> +    if (!s390_has_feat(S390_FEAT_CONFIGURATION_TOPOLOGY)) {
> +        s390_program_interrupt(env, PGM_OPERATION, ra);
> +        return;
> +    }
> +
> +    if (env->psw.mask & PSW_MASK_PSTATE) {
> +        s390_program_interrupt(env, PGM_PRIVILEGED, ra);
> +        return;
> +    }
> +
> +    if (reg & ~S390_TOPO_FC_MASK) {
> +        s390_program_interrupt(env, PGM_SPECIFICATION, ra);
> +        return;
> +    }
> +
> +    switch (fc) {
> +    case S390_CPU_POLARIZATION_VERTICAL:
> +    case S390_CPU_POLARIZATION_HORIZONTAL:

I'd give this a name.
bool requested_vertical = !!fc;

> +        if (s390_topology.vertical_polarization == !!fc) {
> +            env->regs[r1] |= S390_PTF_REASON_DONE;
> +            setcc(cpu, 2);
> +        } else {
> +            s390_topology.vertical_polarization = !!fc;
> +            s390_cpu_topology_set_changed(true);
> +            setcc(cpu, 0);
> +        }
> +        break;
> +    default:
> +        /* Note that fc == 2 is interpreted by the SIE */
> +        s390_program_interrupt(env, PGM_SPECIFICATION, ra);
> +    }
> +}
> +

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