Re: [PATCH v14 17/32] x86/resctrl: Implement resctrl_arch_config_cntr() to assign a counter with ABMC

["Moger, Babu" <babu.moger@amd.com>]

Hi Reinette,

On 6/26/25 13:02, Reinette Chatre wrote:
> Hi Babu,
> 
> On 6/26/25 10:41 AM, Moger, Babu wrote:
>> On 6/24/25 22:03, Reinette Chatre wrote:
>>> On 6/13/25 2:05 PM, Babu Moger wrote:
> 
> ..
> 
>>>> ---
>>>>  arch/x86/kernel/cpu/resctrl/monitor.c | 38 +++++++++++++++++++++++++++
>>>>  include/linux/resctrl.h               | 19 ++++++++++++++
>>>>  2 files changed, 57 insertions(+)
>>>>
>>>> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
>>>> index 0ad9c731c13e..6b0ea4b17c7a 100644
>>>> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
>>>> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
>>>> @@ -444,3 +444,41 @@ bool resctrl_arch_mbm_cntr_assign_enabled(struct rdt_resource *r)
>>>>  {
>>>>  	return resctrl_to_arch_res(r)->mbm_cntr_assign_enabled;
>>>>  }
>>>> +
>>>> +static void resctrl_abmc_config_one_amd(void *info)
>>>> +{
>>>> +	union l3_qos_abmc_cfg *abmc_cfg = info;
>>>> +
>>>> +	wrmsrl(MSR_IA32_L3_QOS_ABMC_CFG, abmc_cfg->full);
>>>> +}
>>>> +
>>>> +/*
>>>> + * Send an IPI to the domain to assign the counter to RMID, event pair.
>>>> + */
>>>> +void resctrl_arch_config_cntr(struct rdt_resource *r, struct rdt_mon_domain *d,
>>>> +			      enum resctrl_event_id evtid, u32 rmid, u32 closid,
>>>> +			      u32 cntr_id, bool assign)
>>>> +{
>>>> +	struct rdt_hw_mon_domain *hw_dom = resctrl_to_arch_mon_dom(d);
>>>> +	union l3_qos_abmc_cfg abmc_cfg = { 0 };
>>>> +	struct arch_mbm_state *am;
>>>> +
>>>> +	abmc_cfg.split.cfg_en = 1;
>>>> +	abmc_cfg.split.cntr_en = assign ? 1 : 0;
>>>> +	abmc_cfg.split.cntr_id = cntr_id;
>>>> +	abmc_cfg.split.bw_src = rmid;
>>>> +	if (assign)
>>>> +		abmc_cfg.split.bw_type = resctrl_get_mon_evt_cfg(evtid);
>>>> +
>>>> +	smp_call_function_any(&d->hdr.cpu_mask, resctrl_abmc_config_one_amd, &abmc_cfg, 1);
>>>
>>> An optimization to consider is to direct the IPI to a housekeeping CPU.
>>> If one exist, a further optimization could be to queue it on that CPU
>>> instead of IPI. Your call since I am not familiar with the use cases here.
>>> Looks like all paths leading to this is triggered by a user space action
>>> (mount, mkdir, or write to update event config). This would require exposing
>>> the housekeeping CPU code to arch.
>>
>> Do you mean something like this?
>>
>> cpu = cpumask_any_housekeeping(&d->hdr.cpu_mask, RESCTRL_PICK_ANY_CPU);
>>
>> smp_call_on_cpu(cpu, resctrl_abmc_config_one_amd, &abmc_cfg, false);
> 
> Please note the returned "cpu" may be nohz_full and if it is it would need
> an IPI. Similar to mon_event_read().
> 

Yes. Got that.

>>
>>
>> You want to do these changes now or later?  It requires few other changes
>> to move around the code.
> 
> I'll leave this up to you. I think it would be ideal if cpumask_any_housekeeping()
> can be hosted in include/linux/cpumask.h instead of moving it around within
> resctrl.
> 

ok. It will be couple more patches to re-arrange all the related code. I
would prefer its done separately.

-- 
Thanks
Babu Moger