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

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

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