Re: [PATCH v9 24/26] x86/resctrl: Update assignments on event configuration changes

[Reinette Chatre <reinette.chatre@intel.com>]

Hi Babu,

On 10/29/24 4:21 PM, Babu Moger wrote:
> Users can modify the configuration of assignable events. Whenever the
> event configuration is updated, MBM assignments must be revised across
> all monitor groups within the impacted domains.

Please revisit the "Changelog" section in 
Documentation/process/maintainer-tip.rst

> 
> Signed-off-by: Babu Moger <babu.moger@amd.com>
> ---
> v9: Again patch changed completely based on the comment.
>     https://lore.kernel.org/lkml/03b278b5-6c15-4d09-9ab7-3317e84a409e@intel.com/
>     Introduced resctrl_mon_event_config_set to handle IPI.
>     But sending another IPI inside IPI causes problem. Kernel reports SMP
>     warning. So, introduced resctrl_arch_update_cntr() to send the command directly.

I see ... the WARN is because there is a check whether IRQs are disabled before
the check whether the function can be run locally.

> 
> v8: Patch changed completely.
>     Updated the assignment on same IPI as the event is updated.
>     Could not do the way we discussed in the thread.
>     https://lore.kernel.org/lkml/f77737ac-d3f6-3e4b-3565-564f79c86ca8@amd.com/
>     Needed to figure out event type to update the configuration.
> 
> v7: New patch to update the assignments. Missed it earlier.
> ---
>  arch/x86/kernel/cpu/resctrl/rdtgroup.c | 86 +++++++++++++++++++++++---
>  include/linux/resctrl.h                |  3 +-
>  2 files changed, 79 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index 5b8bb8bd913c..7646d67ea10e 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -1710,6 +1710,7 @@ static int rdtgroup_size_show(struct kernfs_open_file *of,
>  }
>  
>  struct mon_config_info {
> +	struct rdt_resource *r;
>  	struct rdt_mon_domain *d;
>  	u32 evtid;
>  	u32 mon_config;
> @@ -1735,26 +1736,28 @@ u32 resctrl_arch_mon_event_config_get(struct rdt_mon_domain *d,
>  	return INVALID_CONFIG_VALUE;
>  }
>  
> -void resctrl_arch_mon_event_config_set(void *info)
> +void resctrl_arch_mon_event_config_set(struct rdt_mon_domain *d,
> +				       enum resctrl_event_id eventid, u32 val)
>  {
> -	struct mon_config_info *mon_info = info;
>  	struct rdt_hw_mon_domain *hw_dom;
>  	unsigned int index;
>  
> -	index = mon_event_config_index_get(mon_info->evtid);
> +	index = mon_event_config_index_get(eventid);
>  	if (index == INVALID_CONFIG_INDEX)
>  		return;
>  
> -	wrmsr(MSR_IA32_EVT_CFG_BASE + index, mon_info->mon_config, 0);
> +	wrmsr(MSR_IA32_EVT_CFG_BASE + index, val, 0);
>  
> -	hw_dom = resctrl_to_arch_mon_dom(mon_info->d);
> +	hw_dom = resctrl_to_arch_mon_dom(d);
>  
> -	switch (mon_info->evtid) {
> +	switch (eventid) {
>  	case QOS_L3_MBM_TOTAL_EVENT_ID:
> -		hw_dom->mbm_total_cfg = mon_info->mon_config;
> +		hw_dom->mbm_total_cfg = val;
>  		break;
>  	case QOS_L3_MBM_LOCAL_EVENT_ID:
> -		hw_dom->mbm_local_cfg = mon_info->mon_config;
> +		hw_dom->mbm_local_cfg = val;
> +		break;
> +	default:
>  		break;
>  	}
>  }
> @@ -1826,6 +1829,70 @@ static int mbm_local_bytes_config_show(struct kernfs_open_file *of,
>  	return 0;
>  }
>  
> +static struct rdtgroup *rdtgroup_find_grp_by_cntr_id_index(int cntr_id, unsigned int index)
> +{
> +	struct rdtgroup *prgrp, *crgrp;
> +
> +	/* Check if the cntr_id is associated to the event type updated */
> +	list_for_each_entry(prgrp, &rdt_all_groups, rdtgroup_list) {
> +		if (prgrp->mon.cntr_id[index] == cntr_id)
> +			return prgrp;
> +
> +		list_for_each_entry(crgrp, &prgrp->mon.crdtgrp_list, mon.crdtgrp_list) {
> +			if (crgrp->mon.cntr_id[index] == cntr_id)
> +				return crgrp;
> +		}
> +	}
> +
> +	return NULL;
> +}
> +
> +static void resctrl_arch_update_cntr(struct rdt_resource *r, struct rdt_mon_domain *d,
> +				     enum resctrl_event_id evtid, u32 rmid,
> +				     u32 closid, u32 cntr_id, u32 val)
> +{
> +	union l3_qos_abmc_cfg abmc_cfg = { 0 };
> +
> +	abmc_cfg.split.cfg_en = 1;
> +	abmc_cfg.split.cntr_en = 1;
> +	abmc_cfg.split.cntr_id = cntr_id;
> +	abmc_cfg.split.bw_src = rmid;
> +	abmc_cfg.split.bw_type = val;
> +
> +	wrmsrl(MSR_IA32_L3_QOS_ABMC_CFG, abmc_cfg.full);

Is it needed to create an almost duplicate function? What if instead 
only resctrl_arch_config_cntr() exists and it uses parameter to decide
whether to call resctrl_abmc_config_one_amd() directly or via 
smp_call_function_any()? I think that should help to make clear how
the code flows. 
Also note that this is an almost identical arch callback with no
error return. I expect that building on existing resctrl_arch_config_cntr()
will make things easier to understand.

> +}
> +
> +static void resctrl_mon_event_config_set(void *info)
> +{
> +	struct mon_config_info *mon_info = info;
> +	struct rdt_mon_domain *d = mon_info->d;
> +	struct rdt_resource *r = mon_info->r;

Note that local variable r is created here while the function is inconsistent by
switching between using r and mon_info->r.

> +	struct rdtgroup *rdtgrp;
> +	unsigned int index;
> +	u32 cntr_id;
> +
> +	resctrl_arch_mon_event_config_set(d, mon_info->evtid, mon_info->mon_config);
> +
> +	if (!resctrl_arch_mbm_cntr_assign_enabled(r))
> +		return;
> +
> +	index = mon_event_config_index_get(mon_info->evtid);

This is an AMD arch specific helper to know which offset of an MSR to use. It should
not be used directly in resctrl fs code, this is what MBM_EVENT_ARRAY_INDEX was created for.

Since MBM_EVENT_ARRAY_INDEX is a macro it can be called closer to where it is used,
within  rdtgroup_find_grp_by_cntr_id_index(), which prompts a reconsider of that function name.

> +	if (index == INVALID_CONFIG_INDEX)
> +		return;
> +
> +	for (cntr_id = 0; cntr_id < r->mon.num_mbm_cntrs; cntr_id++) {
> +		if (test_bit(cntr_id, d->mbm_cntr_map)) {
> +			rdtgrp = rdtgroup_find_grp_by_cntr_id_index(cntr_id, index);
> +			if (rdtgrp)
> +				resctrl_arch_update_cntr(mon_info->r, d,
> +							 mon_info->evtid,
> +							 rdtgrp->mon.rmid,
> +							 rdtgrp->closid,
> +							 cntr_id,
> +							 mon_info->mon_config);
> +		}
> +	}
> +}

Could you please add some function comments to explain the flow here? For example,
what should reader consider if there is to rdtgroup found?

Reinette