Re: [PATCH v5 12/16] fs/resctrl: Program kernel mode assignments on CPU hotplug

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

Hi Reinette,

On 9/16/26 00:35, Reinette Chatre wrote:
> Hi Babu,
> 
> On 8/26/26 12:32 PM, Babu Moger wrote:
> 
> 
>> ---
>>   fs/resctrl/rdtgroup.c | 59 +++++++++++++++++++++++++++++++++++++++++++
>>   1 file changed, 59 insertions(+)
>>
>> diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
>> index 06e74b027044..97e4176669e5 100644
>> --- a/fs/resctrl/rdtgroup.c
>> +++ b/fs/resctrl/rdtgroup.c
>> @@ -4951,11 +4951,67 @@ int resctrl_online_mon_domain(struct rdt_resource *r, struct rdt_domain_hdr *hdr
>>   	return err;
>>   }
>>   
>> +/*
>> + * resctrl_kmode_online_cpu() - Program kernel mode association for @cpu
>> + * @cpu: CPU that has just been brought online
>> + *
>> + * If assign_global_enable_per_cpu is active and the rdtgroup has an active
>> + * kernel-mode association, add @cpu to kmode_cpu_mask and program the
>> + * corresponding kernel mode association.
>> + */
>> +static void resctrl_kmode_online_cpu(unsigned int cpu)
>> +{
>> +	struct rdtgroup *rdtgrp = resctrl_kcfg.active.k_rdtgrp;
>> +	bool assign_ctrl, assign_mon;
>> +
>> +	if (resctrl_kcfg.active.kmode_cur != RESCTRL_ASSIGN_GLOBAL_ENABLE_PER_CPU ||
>> +	    !rdtgrp || !rdtgrp->kmode)
>> +		return;
>> +
>> +	assign_ctrl = (resctrl_kcfg.active.ctrl_mode == KMODE_ASSIGN);
>> +	assign_mon = (resctrl_kcfg.active.mon_mode == KMODE_ASSIGN);
>> +
>> +	cpumask_set_cpu(cpu, &rdtgrp->kmode_cpu_mask);
>> +
>> +	resctrl_arch_configure_kmode(cpumask_of(cpu), rdtgrp->closid, assign_ctrl,
>> +				     rdtgrp->mon.rmid, assign_mon, true);
> 
> If I counted right, at end of this series, resctrl_arch_configure_kmode() is called
> six times and _every_ call is preceded with the same two line pattern above:
> 
> 	assign_ctrl = (resctrl_kcfg.active.ctrl_mode == KMODE_ASSIGN);
> 	assign_mon = (resctrl_kcfg.active.mon_mode == KMODE_ASSIGN);
> 
> Could this be simplified with a single helper that does something like:
> 
> static void resctrl_configure_global_kmode(const struct cpumask *mask,
> 					   struct rdtgroup *rdtgrp, bool enable)
> {
>    	resctrl_arch_configure_global_kmode(mask, rdtgrp->closid,
>    					    resctrl_kcfg.active.ctrl_mode == KMODE_ASSIGN,
> 					    rdtgrp->mon.rmid,
> 					    resctrl_kcfg.active.mon_mode == KMODE_ASSIGN,
> 					    enable);
> }
> 

Sure. That will do. Thanks.

> 
>> +}
>> +
>> +/*
>> + * resctrl_kmode_offline_cpu() - Clear kernel mode association for @cpu
>> + * @cpu: CPU being taken offline.
>> + *
>> + * If assign_global_enable_per_cpu is active, disable the kernel mode
>> + * association for @cpu and remove it from kmode_cpu_mask.
>> + */
>> +static void resctrl_kmode_offline_cpu(unsigned int cpu)
>> +{
>> +	struct rdtgroup *rdtgrp = resctrl_kcfg.active.k_rdtgrp;
>> +	bool assign_ctrl, assign_mon;
>> +
>> +	if (resctrl_kcfg.active.kmode_cur != RESCTRL_ASSIGN_GLOBAL_ENABLE_PER_CPU ||
>> +	    !rdtgrp || !rdtgrp->kmode)
>> +		return;
>> +
>> +	if (!cpumask_test_cpu(cpu, &rdtgrp->kmode_cpu_mask))
>> +		return;
>> +
>> +	assign_ctrl = (resctrl_kcfg.active.ctrl_mode == KMODE_ASSIGN);
>> +	assign_mon = (resctrl_kcfg.active.mon_mode == KMODE_ASSIGN);
>> +
>> +	cpumask_clear_cpu(cpu, &rdtgrp->kmode_cpu_mask);
>> +
>> +	resctrl_arch_configure_kmode(cpumask_of(cpu), rdtgrp->closid, assign_ctrl,
>> +				     rdtgrp->mon.rmid, assign_mon, false);
>> +}
>> +
>>   void resctrl_online_cpu(unsigned int cpu)
>>   {
>>   	mutex_lock(&rdtgroup_mutex);
>>   	/* The CPU is set in default rdtgroup after online. */
>>   	cpumask_set_cpu(cpu, &rdtgroup_default.cpu_mask);
>> +	/* Program any active kernel mode association on this CPU. */
> 
> This comment is not helpful.

Will remove these comments.

Thanks
Babu