Re: [PATCH v4 2/5] spapr_numa.c: split FORM1 code into helpers

[Daniel Henrique Barboza <danielhb413@gmail.com>]

On 9/6/21 9:30 PM, David Gibson wrote:
> On Fri, Aug 27, 2021 at 06:24:52AM -0300, Daniel Henrique Barboza wrote:
>> The upcoming FORM2 NUMA affinity will support asymmetric NUMA topologies
>> and doesn't need be concerned with all the legacy support for older
>> pseries FORM1 guests.
>>
>> We're also not going to calculate associativity domains based on numa
>> distance (via spapr_numa_define_associativity_domains) since the
>> distances will be written directly into new DT properties.
>>
>> Let's split FORM1 code into its own functions to allow for easier
>> insertion of FORM2 logic later on.
>>
>> Reviewed-by: Greg Kurz <groug@kaod.org>
>> Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
>> ---
>>   hw/ppc/spapr_numa.c | 61 +++++++++++++++++++++++++++++----------------
>>   1 file changed, 39 insertions(+), 22 deletions(-)
>>
>> diff --git a/hw/ppc/spapr_numa.c b/hw/ppc/spapr_numa.c
>> index 779f18b994..04a86f9b5b 100644
>> --- a/hw/ppc/spapr_numa.c
>> +++ b/hw/ppc/spapr_numa.c
>> @@ -155,6 +155,32 @@ static void spapr_numa_define_associativity_domains(SpaprMachineState *spapr)
>>   
>>   }
>>   
>> +/*
>> + * Set NUMA machine state data based on FORM1 affinity semantics.
>> + */
>> +static void spapr_numa_FORM1_affinity_init(SpaprMachineState *spapr,
>> +                                           MachineState *machine)
>> +{
>> +    bool using_legacy_numa = spapr_machine_using_legacy_numa(spapr);
>> +
>> +    /*
>> +     * Legacy NUMA guests (pseries-5.1 and older, or guests with only
>> +     * 1 NUMA node) will not benefit from anything we're going to do
>> +     * after this point.
>> +     */
>> +    if (using_legacy_numa) {
>> +        return;
>> +    }
> 
> My only concern with this patch is that handling the
> "using_legacy_numa" case might logically belong outside the FORM1
> code.  I mean, I'm pretty sure using_legacy_numa implies FORM1 in
> practice, but conceptually it seems like a more fundamental question
> than the DT encoding of the NUMA information.

I'll carry on this suggestion for the next spin, v6, given that the v5 I sent
a few minutes ago is also verifying legacy numa in FORM1 code.


Thanks,


Daniel

> 
>> +
>> +    if (!spapr_numa_is_symmetrical(machine)) {
>> +        error_report("Asymmetrical NUMA topologies aren't supported "
>> +                     "in the pSeries machine");
>> +        exit(EXIT_FAILURE);
>> +    }
>> +
>> +    spapr_numa_define_associativity_domains(spapr);
>> +}
>> +
>>   void spapr_numa_associativity_init(SpaprMachineState *spapr,
>>                                      MachineState *machine)
>>   {
>> @@ -210,22 +236,7 @@ void spapr_numa_associativity_init(SpaprMachineState *spapr,
>>           spapr->numa_assoc_array[i][MAX_DISTANCE_REF_POINTS] = cpu_to_be32(i);
>>       }
>>   
>> -    /*
>> -     * Legacy NUMA guests (pseries-5.1 and older, or guests with only
>> -     * 1 NUMA node) will not benefit from anything we're going to do
>> -     * after this point.
>> -     */
>> -    if (using_legacy_numa) {
>> -        return;
>> -    }
>> -
>> -    if (!spapr_numa_is_symmetrical(machine)) {
>> -        error_report("Asymmetrical NUMA topologies aren't supported "
>> -                     "in the pSeries machine");
>> -        exit(EXIT_FAILURE);
>> -    }
>> -
>> -    spapr_numa_define_associativity_domains(spapr);
>> +    spapr_numa_FORM1_affinity_init(spapr, machine);
>>   }
>>   
>>   void spapr_numa_write_associativity_dt(SpaprMachineState *spapr, void *fdt,
>> @@ -302,12 +313,8 @@ int spapr_numa_write_assoc_lookup_arrays(SpaprMachineState *spapr, void *fdt,
>>       return ret;
>>   }
>>   
>> -/*
>> - * Helper that writes ibm,associativity-reference-points and
>> - * max-associativity-domains in the RTAS pointed by @rtas
>> - * in the DT @fdt.
>> - */
>> -void spapr_numa_write_rtas_dt(SpaprMachineState *spapr, void *fdt, int rtas)
>> +static void spapr_numa_FORM1_write_rtas_dt(SpaprMachineState *spapr,
>> +                                           void *fdt, int rtas)
>>   {
>>       MachineState *ms = MACHINE(spapr);
>>       SpaprMachineClass *smc = SPAPR_MACHINE_GET_CLASS(spapr);
>> @@ -365,6 +372,16 @@ void spapr_numa_write_rtas_dt(SpaprMachineState *spapr, void *fdt, int rtas)
>>                        maxdomains, sizeof(maxdomains)));
>>   }
>>   
>> +/*
>> + * Helper that writes ibm,associativity-reference-points and
>> + * max-associativity-domains in the RTAS pointed by @rtas
>> + * in the DT @fdt.
>> + */
>> +void spapr_numa_write_rtas_dt(SpaprMachineState *spapr, void *fdt, int rtas)
>> +{
>> +    spapr_numa_FORM1_write_rtas_dt(spapr, fdt, rtas);
>> +}
>> +
>>   static target_ulong h_home_node_associativity(PowerPCCPU *cpu,
>>                                                 SpaprMachineState *spapr,
>>                                                 target_ulong opcode,
>