Re: [PATCH v2 2/5] s390x: kvm: topology: interception of PTF instruction

[Thomas Huth <thuth@redhat.com>]

On 22/07/2021 19.42, Pierre Morel wrote:
> Interception of the PTF instruction depending on the new
> KVM_CAP_S390_CPU_TOPOLOGY KVM extension.
> 
> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
> ---
>   hw/s390x/s390-virtio-ccw.c         | 45 ++++++++++++++++++++++++++++++
>   include/hw/s390x/s390-virtio-ccw.h |  7 +++++
>   target/s390x/kvm/kvm.c             | 21 ++++++++++++++
>   3 files changed, 73 insertions(+)
> 
> diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
> index e4b18aef49..500e856974 100644
> --- a/hw/s390x/s390-virtio-ccw.c
> +++ b/hw/s390x/s390-virtio-ccw.c
> @@ -404,6 +404,49 @@ static void s390_pv_prepare_reset(S390CcwMachineState *ms)
>       s390_pv_prep_reset();
>   }
>   
> +int s390_handle_ptf(S390CPU *cpu, uint8_t r1, uintptr_t ra)
> +{
> +    S390CcwMachineState *ms = S390_CCW_MACHINE(qdev_get_machine());
> +    CPUS390XState *env = &cpu->env;
> +    uint64_t reg = env->regs[r1];
> +    uint8_t fc = reg & S390_TOPO_FC_MASK;
> +
> +    if (!s390_has_feat(S390_FEAT_CONFIGURATION_TOPOLOGY)) {
> +        s390_program_interrupt(env, PGM_OPERAND, ra);

I think that should be PGM_OPERATION instead?

> +        return 0;
> +    }
> +
> +    if (env->psw.mask & PSW_MASK_PSTATE) {
> +        s390_program_interrupt(env, PGM_PRIVILEGED, ra);
> +        return 0;
> +    }
> +
> +    if (reg & ~S390_TOPO_FC_MASK) {
> +        s390_program_interrupt(env, PGM_SPECIFICATION, ra);
> +        return 0;
> +    }
> +
> +    switch (fc) {
> +    case 0:    /* Horizontal polarization is already set */
> +        env->regs[r1] = S390_PTF_REASON_DONE; > +        return 2;
> +    case 1:    /* Vertical polarization is not supported */
> +        env->regs[r1] = S390_PTF_REASON_NONE;


This way, you're clearing the bits in the FC field. Is this intended by the 
architecture? If I get the PoP right, it just sets the bits in the RC field, 
but likely it should not clear the 1 in the FC field? Did you try on LPAR or 
z/VM to see what happens there?

> +        return 2;
> +    case 2:    /* Report if a topology change report is pending */
> +        if (ms->topology_change_report_pending) {
> +            ms->topology_change_report_pending = false;
> +            return 1;
> +        }
> +        return 0;
> +    default:
> +        s390_program_interrupt(env, PGM_SPECIFICATION, ra);
> +        break;

Just a matter of taste - but you could drop the break here.

> +    }
> +
> +    return 0;
> +}
> +
>   static void s390_machine_reset(MachineState *machine)
>   {
>       S390CcwMachineState *ms = S390_CCW_MACHINE(machine);
> @@ -433,6 +476,8 @@ static void s390_machine_reset(MachineState *machine)
>           run_on_cpu(cs, s390_do_cpu_ipl, RUN_ON_CPU_NULL);
>           break;
>       case S390_RESET_MODIFIED_CLEAR:
> +        /* clear topology_change_report pending condition on subsystem reset */
> +        ms->topology_change_report_pending = false;
>           /*
>            * Susbsystem reset needs to be done before we unshare memory
>            * and lose access to VIRTIO structures in guest memory.
> diff --git a/include/hw/s390x/s390-virtio-ccw.h b/include/hw/s390x/s390-virtio-ccw.h
> index 3331990e02..fbde357332 100644
> --- a/include/hw/s390x/s390-virtio-ccw.h
> +++ b/include/hw/s390x/s390-virtio-ccw.h
> @@ -27,9 +27,16 @@ struct S390CcwMachineState {
>       bool aes_key_wrap;
>       bool dea_key_wrap;
>       bool pv;
> +    bool topology_change_report_pending;
>       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
> +int s390_handle_ptf(S390CPU *cpu, uint8_t r1, uintptr_t ra);
> +
>   struct S390CcwMachineClass {
>       /*< private >*/
>       MachineClass parent_class;
> diff --git a/target/s390x/kvm/kvm.c b/target/s390x/kvm/kvm.c
> index 5b1fdb55c4..9a0c13d4ac 100644
> --- a/target/s390x/kvm/kvm.c
> +++ b/target/s390x/kvm/kvm.c
> @@ -97,6 +97,7 @@
>   
>   #define PRIV_B9_EQBS                    0x9c
>   #define PRIV_B9_CLP                     0xa0
> +#define PRIV_B9_PTF                     0xa2
>   #define PRIV_B9_PCISTG                  0xd0
>   #define PRIV_B9_PCILG                   0xd2
>   #define PRIV_B9_RPCIT                   0xd3
> @@ -1452,6 +1453,16 @@ static int kvm_mpcifc_service_call(S390CPU *cpu, struct kvm_run *run)
>       }
>   }
>   
> +static int kvm_handle_ptf(S390CPU *cpu, struct kvm_run *run)
> +{
> +    uint8_t r1 = (run->s390_sieic.ipb >> 20) & 0x0f;
> +    uint8_t ret;

Why is ret an uint8_t ? s390_handle_ptf() returns an "int".

> +    ret = s390_handle_ptf(cpu, r1, RA_IGNORED);
> +    setcc(cpu, ret);
> +    return 0; > +}

  Thomas