Re: [PATCH v4 14/19] x86/resctrl: Add the interface to assign ABMC counter

Reinette Chatre
2024-06-20T22:50:35Z

Hi Babu,

On 6/19/24 3:38 PM, Moger, Babu wrote:
> On 6/13/2024 8:48 PM, Reinette Chatre wrote:
>> On 5/24/24 5:23 AM, Babu Moger wrote:

>>> +int resctrl_arch_assign(struct rdt_domain *d, u32 evtid, u32 rmid,
>>> +            u32 ctr_id, u32 closid, bool enable)
>>> +{
>>> +    struct rdt_hw_domain *hw_dom = resctrl_to_arch_dom(d);
>>> +    union l3_qos_abmc_cfg abmc_cfg = { 0 };
>>> +    struct arch_mbm_state *arch_mbm;
>>> +
>>> +    abmc_cfg.split.cfg_en = 1;
>>> +    abmc_cfg.split.ctr_en = enable ? 1 : 0;
>>> +    abmc_cfg.split.ctr_id = ctr_id;
>>> +    abmc_cfg.split.bw_src = rmid;
>>> +
>>> +    /*
>>> +     * Read the event configuration from the domain and pass it as
>>> +     * bw_type.
>>> +     */
>>> +    if (evtid == QOS_L3_MBM_TOTAL_EVENT_ID) {
>>> +        abmc_cfg.split.bw_type = hw_dom->mbm_total_cfg;
>>> +        arch_mbm = &hw_dom->arch_mbm_total[rmid];
>>> +    } else {
>>> +        abmc_cfg.split.bw_type = hw_dom->mbm_local_cfg;
>>> +        arch_mbm = &hw_dom->arch_mbm_local[rmid];
>>> +    }
>>> +
>>> +    smp_call_function_any(&d->cpu_mask, rdtgroup_abmc_cfg, &abmc_cfg, 1);
>>> +
>>> +    /* Reset the internal counters */
>>
>> "internal counters"? This needs a definition ... but since this is not
>> a new data structure the comment can be more specific about what is done
>> and why.
>
> How about?
> /* Reset internal mbm event counters. */

I think it is potentially confusing to introduce a new concept of
"internal counters". This is just the architectural state helping to
detect overflows. This commit has no mention of this but I assume that
the re-configuration of the counter will reset it, which explains
why it is required to reset the state maintained by software.
A similar comment to what can be found in mbm_config_write_domain()
would be useful. This does not have to be so elaborate, maybe just something
like (please feel free to improve):

Configuring a hardware counter resets it. Reset architectural
state to match.

Reinette