linux-kernel - Re: [PATCH v2 07/18] x86/resctrl: Move CLOSID/RMID matching and setting to use helpers

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Message-ID: <4002faaa-d93a-0d9b-0234-05bfae3d7b93@arm.com>
Date:   Mon, 6 Mar 2023 11:32:10 +0000
From:   James Morse <james.morse@....com>
To:     Reinette Chatre <reinette.chatre@...el.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Cc:     Fenghua Yu <fenghua.yu@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        H Peter Anvin <hpa@...or.com>,
        Babu Moger <Babu.Moger@....com>,
        shameerali.kolothum.thodi@...wei.com,
        D Scott Phillips OS <scott@...amperecomputing.com>,
        carl@...amperecomputing.com, lcherian@...vell.com,
        bobo.shaobowang@...wei.com, tan.shaopeng@...itsu.com,
        xingxin.hx@...nanolis.org, baolin.wang@...ux.alibaba.com,
        Jamie Iles <quic_jiles@...cinc.com>,
        Xin Hao <xhao@...ux.alibaba.com>, peternewman@...gle.com
Subject: Re: [PATCH v2 07/18] x86/resctrl: Move CLOSID/RMID matching and
 setting to use helpers

Hi Reinette,

On 02/02/2023 23:47, Reinette Chatre wrote:
> On 1/13/2023 9:54 AM, James Morse wrote:
> 
> ...
> 
>> @@ -567,19 +579,14 @@ static int __rdtgroup_move_task(struct task_struct *tsk,
>>  	 * For monitor groups, can move the tasks only from
>>  	 * their parent CTRL group.
>>  	 */
>> -
>> -	if (rdtgrp->type == RDTCTRL_GROUP) {
>> -		WRITE_ONCE(tsk->closid, rdtgrp->closid);
>> -		WRITE_ONCE(tsk->rmid, rdtgrp->mon.rmid);
>> -	} else if (rdtgrp->type == RDTMON_GROUP) {
>> -		if (rdtgrp->mon.parent->closid == tsk->closid) {
>> -			WRITE_ONCE(tsk->rmid, rdtgrp->mon.rmid);
>> -		} else {
>> -			rdt_last_cmd_puts("Can't move task to different control group\n");
>> -			return -EINVAL;
>> -		}
>> +	if (rdtgrp->type == RDTMON_GROUP &&
>> +	    !resctrl_arch_match_closid(tsk, rdtgrp->mon.parent->closid)) {
>> +		rdt_last_cmd_puts("Can't move task to different control group\n");
>> +		return -EINVAL;
>>  	}
>>  
>> +	resctrl_arch_set_closid_rmid(tsk, rdtgrp->closid, rdtgrp->mon.rmid);
> 
> This does not use the intended closid when rdtgrp->type == RDTMON_GROUP.

Yes, it should be rdtgrp->mon.parent->closid.

rdtgroup_mkdir_mon() initialises them to be the same, I guess its Peter's monitor-group
rename that means this could get the wrong value?

I've fixed it as:
---------%<---------
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index c7392d10dc5b..30d8961b833c 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -585,7 +585,12 @@ static int __rdtgroup_move_task(struct task_struct *tsk,
                return -EINVAL;
        }

-       resctrl_arch_set_closid_rmid(tsk, rdtgrp->closid, rdtgrp->mon.rmid);
+       if (rdtgrp->type == RDTMON_GROUP)
+               resctrl_arch_set_closid_rmid(tsk, rdtgrp->mon.parent->closid,
+                                            rdtgrp->mon.rmid);
+       else
+               resctrl_arch_set_closid_rmid(tsk, rdtgrp->closid,
+                                            rdtgrp->mon.rmid);

        /*
         * Ensure the task's closid and rmid are written before determining if
---------%<---------


Thanks,

James