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

[Babu Moger]

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