linux-kernel - Re: [PATCH v4 02/24] x86/resctrl: Split struct rdt

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Date:   Thu, 17 Jun 2021 18:02:15 +0100
From:   James Morse <james.morse@....com>
To:     Babu Moger <babu.moger@....com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Cc:     Fenghua Yu <fenghua.yu@...el.com>,
        Reinette Chatre <reinette.chatre@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        H Peter Anvin <hpa@...or.com>,
        shameerali.kolothum.thodi@...wei.com,
        Jamie Iles <jamie@...iainc.com>,
        D Scott Phillips OS <scott@...amperecomputing.com>,
        lcherian@...vell.com
Subject: Re: [PATCH v4 02/24] x86/resctrl: Split struct rdt_domain

Hi Babu,

On 15/06/2021 18:51, Babu Moger wrote:
> On 6/14/21 3:09 PM, James Morse wrote:
>> resctrl is the defacto Linux ABI for SoC resource partitioning features.
>>
>> To support it on another architecture, it needs to be abstracted from
>> the features provided by Intel RDT and AMD PQoS, and moved to /fs/.
>> struct rdt_resource contains a mix of architecture private details
>> and properties of the filesystem interface user-space users.
>>
>> Continue by splitting struct rdt_domain, into an architecture private
>> 'hw' struct, which contains the common resctrl structure that would be
>> used by any architecture. The hardware values in ctrl_val and mbps_val
>> need to be accessed via helpers to allow another architecture to convert
>> these into a different format if necessary. After this split, filesystem
>> code paths touching a 'hw' struct indicates where an abstraction
>> is needed.
>>
>> Splitting this structure only moves types around, and should not lead
>> to any change in behaviour.

>> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
>> index 43c8cf6b2b12..235cf621c878 100644
>> --- a/arch/x86/kernel/cpu/resctrl/internal.h
>> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
>> @@ -299,44 +299,25 @@ struct mbm_state {

>> -struct rdt_domain {
>> -	struct list_head		list;
>> -	int				id;
>> -	struct cpumask			cpu_mask;
>> -	unsigned long			*rmid_busy_llc;
>> -	struct mbm_state		*mbm_total;
>> -	struct mbm_state		*mbm_local;
>> -	struct delayed_work		mbm_over;
>> -	struct delayed_work		cqm_limbo;
>> -	int				mbm_work_cpu;
>> -	int				cqm_work_cpu;
>> +struct rdt_hw_domain {
>> +	struct rdt_domain		resctrl;


> Naming is bit confusing here. There is another field with the same
> name(patch1).

But a totally different type, you'd only access its members via the resource or domain, so
its always clear which it is. (and if you get them wrong, it won't build)


> +struct rdt_hw_resource {
> +	struct rdt_resource	resctrl;
> 
> I think we should make this bit more clearer. May be or something similar.
> 
> struct rdt_hw_domain {
>     struct rdt_domain		d_resctrl;
Sure, I guess it makes it clear when quoting something.


Thanks,

James