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

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

Hi Reinette,

On 12/19/2024 5:39 PM, Reinette Chatre wrote:
> 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()).

Yes. Will do.

> 
> ...
> 
>>   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" ...

Sure.

> 
>> @@ -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().

Sure.
> 
>> @@ -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.

Sure.

Thanks
Babu