linux-kernel - Re: [PATCH v5 14/40] x86/resctrl: Add a resctrl helper to reset all the resources

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Message-ID: <55dc287f-1277-40fa-9d68-baf6393beb3c@arm.com>
Date: Fri, 7 Feb 2025 15:43:01 +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,
 baolin.wang@...ux.alibaba.com, Jamie Iles <quic_jiles@...cinc.com>,
 Xin Hao <xhao@...ux.alibaba.com>, peternewman@...gle.com,
 dfustini@...libre.com, amitsinght@...vell.com,
 David Hildenbrand <david@...hat.com>, Rex Nie <rex.nie@...uarmicro.com>,
 Dave Martin <dave.martin@....com>, Shaopeng Tan <tan.shaopeng@...fujitsu.com>
Subject: Re: [PATCH v5 14/40] x86/resctrl: Add a resctrl helper to reset all
 the resources

Hi Reinette,

On 23/10/2024 22:32, Reinette Chatre wrote:
> On 10/4/24 11:03 AM, James Morse wrote:
>> On umount(), resctrl resets each resource back to its default
>> configuration. It only ever does this for all resources in one go.
>>
>> reset_all_ctrls() is architecture specific as it works with struct
>> rdt_hw_resource.
>>
>> Add an architecture helper to reset all resources.

>> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> index 61c8add103fe..a15198f90b29 100644
>> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
>> @@ -2883,6 +2883,14 @@ static int reset_all_ctrls(struct rdt_resource *r)
>>  	return 0;
>>  }
>>  
>> +void resctrl_arch_reset_resources(void)
>> +{
>> +	struct rdt_resource *r;
>> +
>> +	for_each_alloc_capable_rdt_resource(r)
>> +		reset_all_ctrls(r);
>> +}

> Wouldn't this require all archs to have a duplicate helper as above with
> only the resctrl_all_ctrls() actually being arch specific? 

I was hoping to be able to save a few IPI by doing the per-core work once, instead of
per-resource-per-core ... but its only done on umount, so I doubt anyone will complain!


> What if it is instead:
> 	resctrl_reset_alloc_resources() or reset_alloc_resources() or ...
> 	{
> 		struct rdt_resource *r;
> 	
> 		for_each_alloc_capable_rdt_resource(r)
> 			resctrl_arch_reset_all_ctrls(r);
> 	}
> 
> With above archs only need to implement the actual reset code.

I opted for one helper that does everything as that is the only example today.
This has the advantage that the filesystem code can now reset a specific resource.

Sure, lets do that.


Thanks,

James

[0] https://lore.kernel.org/all/20230419111111.477118-8-dfustini@baylibre.com/