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

[Pierre Morel]

On 9/6/21 7:21 PM, Thomas Huth wrote:
> 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?

Right, I thought I did do the modification since v1.
Seems I forgot or it get lost :(
I will take care of this for the next time.

> > +        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?

You are right, the FC field is not changed on LPAR.

> > +        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.

ok

> > +    }
> > +
> > +    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".

No reason, I must have use the same type as the line before.
I change to int.

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

Thanks for the comments,
Pierre

--
Pierre Morel
IBM Lab Boeblingen