Re: [PATCH v14 06/11] s390x/cpu topology: interception of PTF instruction

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

On 1/16/23 19:24, Nina Schoetterl-Glausch wrote:
> On Thu, 2023-01-05 at 15:53 +0100, 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 hypervizor 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 hypervizor.
>>
>> During RESET all CPU of the configuration are placed in
>> horizontal polarity.
>>
>> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
>> ---
>>   include/hw/s390x/cpu-topology.h    |  3 +
>>   include/hw/s390x/s390-virtio-ccw.h |  6 ++
>>   target/s390x/cpu.h                 |  1 +
>>   hw/s390x/cpu-topology.c            | 92 ++++++++++++++++++++++++++++++
>>   target/s390x/cpu-sysemu.c          | 16 ++++++
>>   target/s390x/kvm/kvm.c             | 11 ++++
>>   6 files changed, 129 insertions(+)
>>
>> diff --git a/include/hw/s390x/cpu-topology.h b/include/hw/s390x/cpu-topology.h
>> index 9571aa70e5..33e23d78b9 100644
>> --- a/include/hw/s390x/cpu-topology.h
>> +++ b/include/hw/s390x/cpu-topology.h
>> @@ -55,11 +55,13 @@ typedef struct S390Topology {
>>       QTAILQ_HEAD(, S390TopologyEntry) list;
>>       uint8_t *sockets;
>>       CpuTopology *smp;
>> +    int polarity;
>>   } S390Topology;
>>   
>>   #ifdef CONFIG_KVM
>>   bool s390_has_topology(void);
>>   void s390_topology_set_cpu(MachineState *ms, S390CPU *cpu, Error **errp);
>> +void s390_topology_set_polarity(int polarity);
>>   #else
>>   static inline bool s390_has_topology(void)
>>   {
>> @@ -68,6 +70,7 @@ static inline bool s390_has_topology(void)
>>   static inline void s390_topology_set_cpu(MachineState *ms,
>>                                            S390CPU *cpu,
>>                                            Error **errp) {}
>> +static inline void s390_topology_set_polarity(int polarity) {}
>>   #endif
>>   extern S390Topology s390_topology;
>>   
>> 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/target/s390x/cpu.h b/target/s390x/cpu.h
>> index 01ade07009..5da4041576 100644
>> --- a/target/s390x/cpu.h
>> +++ b/target/s390x/cpu.h
>> @@ -864,6 +864,7 @@ void s390_do_cpu_set_diag318(CPUState *cs, run_on_cpu_data arg);
>>   int s390_assign_subch_ioeventfd(EventNotifier *notifier, uint32_t sch_id,
>>                                   int vq, bool assign);
>>   void s390_cpu_topology_reset(void);
>> +void s390_cpu_topology_set(void);
> 
> I don't like this name much, it's nondescript.
> s390_cpu_topology_set_modified ?
> 
>>   #ifndef CONFIG_USER_ONLY
>>   unsigned int s390_cpu_set_state(uint8_t cpu_state, S390CPU *cpu);
>>   #else
>> diff --git a/hw/s390x/cpu-topology.c b/hw/s390x/cpu-topology.c
>> index 438055c612..e6b4692581 100644
>> --- a/hw/s390x/cpu-topology.c
>> +++ b/hw/s390x/cpu-topology.c
>> @@ -97,6 +97,98 @@ static s390_topology_id s390_topology_from_cpu(S390CPU *cpu)
>>   }
>>   
>>   /**
>> + * s390_topology_set_polarity
>> + * @polarity: horizontal or vertical
>> + *
>> + * Changes the polarity of all the CPU in the configuration.
>> + *
>> + * If the dedicated CPU modifier attribute is set a vertical
>> + * polarization is always high (Architecture).
>> + * Otherwise we decide to set it as medium.
>> + *
>> + * Once done, advertise a topology change.
>> + */
>> +void s390_topology_set_polarity(int polarity)
> 
> I don't like that this function ignores what kind of vertical polarization is passed,
> it's confusing.
> That seems like a further reason to split horizontal/vertical from the entitlement.
> 

Yes.
I will also make the ordering of the TLE at the last moment instead of 
doing it during hotplug or QAPI command.
This is something Cedric proposed some time ago and I think it is right, 
it will be easier to do it once in STSI than on every change of topology,
hotplug, QAPI and polarization change with PTF.

Regards,
Pierre

-- 
Pierre Morel
IBM Lab Boeblingen