Re: [PATCH v10 18/24] x86/resctrl: Auto assign/unassign counters when mbm_cntr_assign is enabled

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

Hi Babu,

On 12/12/24 12:15 PM, Babu Moger wrote:
> Assign/unassign counters on resctrl group creation/deletion. Two counters
> are required per group, one for MBM total event and one for MBM local
> event.
> 
> There are a limited number of counters available for assignment. If these
> counters are exhausted, the kernel will display the error message: "Out of
> MBM assignable counters". However, it is not necessary to fail the
> creation of a group due to assignment failures. Users have the flexibility
> to modify the assignments at a later time.
> 
> Signed-off-by: Babu Moger <babu.moger@amd.com>
> ---
> ---
>  arch/x86/kernel/cpu/resctrl/rdtgroup.c | 81 +++++++++++++++++++++++++-
>  1 file changed, 79 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index a71a8389b649..5acae525881a 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -920,6 +920,25 @@ static int rdtgroup_available_mbm_cntrs_show(struct kernfs_open_file *of,
>  	return ret;
>  }
>  
> +static void mbm_cntr_reset(struct rdt_resource *r)
> +{
> +	struct rdt_mon_domain *dom;
> +
> +	/*
> +	 * Hardware counters will reset after switching the monitor mode.
> +	 * Reset the architectural state so that reading of hardware
> +	 * counter is not considered as an overflow in the next update.
> +	 * Also reset the domain counter bitmap.
> +	 */
> +	if (is_mbm_enabled() && r->mon.mbm_cntr_assignable) {
> +		list_for_each_entry(dom, &r->mon_domains, hdr.list) {
> +			memset(dom->cntr_cfg, 0,
> +			       sizeof(*dom->cntr_cfg) * r->mon.num_mbm_cntrs);
> +			resctrl_arch_reset_rmid_all(r, dom);

This looks to be missing reset of resctrl monitor state (from get_mbm_state()).

...

>  static int rdt_get_tree(struct fs_context *fc)
>  {
>  	struct rdt_fs_context *ctx = rdt_fc2context(fc);
> @@ -3023,6 +3082,8 @@ static int rdt_get_tree(struct fs_context *fc)
>  		if (ret < 0)
>  			goto out_info;
>  
> +		rdtgroup_assign_cntrs(&rdtgroup_default);
> +
>  		ret = mkdir_mondata_all(rdtgroup_default.kn,
>  					&rdtgroup_default, &kn_mondata);
>  		if (ret < 0)

If this mkdir_mondata_all() fails it calls "goto out_mongrp" ...

> @@ -3058,8 +3119,10 @@ static int rdt_get_tree(struct fs_context *fc)
>  out_psl:
>  	rdt_pseudo_lock_release();
>  out_mondata:
> -	if (resctrl_arch_mon_capable())
> +	if (resctrl_arch_mon_capable()) {
>  		kernfs_remove(kn_mondata);
> +		rdtgroup_unassign_cntrs(&rdtgroup_default);
> +	}
>  out_mongrp:
>  	if (resctrl_arch_mon_capable())
>  		kernfs_remove(kn_mongrp);

Looks like this will miss counter cleanup on failure of mkdir_mondata_all().

> @@ -3238,6 +3301,7 @@ static void free_all_child_rdtgrp(struct rdtgroup *rdtgrp)
>  
>  	head = &rdtgrp->mon.crdtgrp_list;
>  	list_for_each_entry_safe(sentry, stmp, head, mon.crdtgrp_list) {
> +		rdtgroup_unassign_cntrs(sentry);
>  		free_rmid(sentry->closid, sentry->mon.rmid);
>  		list_del(&sentry->mon.crdtgrp_list);
>  
> @@ -3278,6 +3342,8 @@ static void rmdir_all_sub(void)
>  		cpumask_or(&rdtgroup_default.cpu_mask,
>  			   &rdtgroup_default.cpu_mask, &rdtgrp->cpu_mask);
>  
> +		rdtgroup_unassign_cntrs(rdtgrp);
> +
>  		free_rmid(rdtgrp->closid, rdtgrp->mon.rmid);
>  
>  		kernfs_remove(rdtgrp->kn);
> @@ -3309,6 +3375,8 @@ static void rdt_kill_sb(struct super_block *sb)
>  	for_each_alloc_capable_rdt_resource(r)
>  		reset_all_ctrls(r);
>  	rmdir_all_sub();
> +	rdtgroup_unassign_cntrs(&rdtgroup_default);
> +	mbm_cntr_reset(&rdt_resources_all[RDT_RESOURCE_L3].r_resctrl);
>  	rdt_pseudo_lock_release();
>  	rdtgroup_default.mode = RDT_MODE_SHAREABLE;
>  	schemata_list_destroy();
> @@ -3772,6 +3840,8 @@ static int mkdir_rdt_prepare_rmid_alloc(struct rdtgroup *rdtgrp)
>  	}
>  	rdtgrp->mon.rmid = ret;
>  
> +	rdtgroup_assign_cntrs(rdtgrp);
> +
>  	ret = mkdir_mondata_all(rdtgrp->kn, rdtgrp, &rdtgrp->mon.mon_data_kn);
>  	if (ret) {
>  		rdt_last_cmd_puts("kernfs subdir error\n");

Cleanup of assigned counters if mkdir_mondata_all() fails seems to be missing here also.

> @@ -3784,8 +3854,10 @@ static int mkdir_rdt_prepare_rmid_alloc(struct rdtgroup *rdtgrp)
>  
>  static void mkdir_rdt_prepare_rmid_free(struct rdtgroup *rgrp)
>  {
> -	if (resctrl_arch_mon_capable())
> +	if (resctrl_arch_mon_capable()) {
> +		rdtgroup_unassign_cntrs(rgrp);
>  		free_rmid(rgrp->closid, rgrp->mon.rmid);
> +	}
>  }
>  
>  static int mkdir_rdt_prepare(struct kernfs_node *parent_kn,
> @@ -4044,6 +4116,9 @@ static int rdtgroup_rmdir_mon(struct rdtgroup *rdtgrp, cpumask_var_t tmpmask)
>  	update_closid_rmid(tmpmask, NULL);
>  
>  	rdtgrp->flags = RDT_DELETED;
> +
> +	rdtgroup_unassign_cntrs(rdtgrp);
> +
>  	free_rmid(rdtgrp->closid, rdtgrp->mon.rmid);
>  
>  	/*
> @@ -4090,6 +4165,8 @@ static int rdtgroup_rmdir_ctrl(struct rdtgroup *rdtgrp, cpumask_var_t tmpmask)
>  	cpumask_or(tmpmask, tmpmask, &rdtgrp->cpu_mask);
>  	update_closid_rmid(tmpmask, NULL);
>  
> +	rdtgroup_unassign_cntrs(rdtgrp);
> +
>  	free_rmid(rdtgrp->closid, rdtgrp->mon.rmid);
>  	closid_free(rdtgrp->closid);
>  

Reinette