linux-kernel - Re: [PATCH v6 18/42] x86/resctrl: Move the is_mbm_*

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Message-ID: <3b0ac0aa-dcc1-429f-9822-f1b0c55b162a@intel.com>
Date: Wed, 19 Feb 2025 15:55:24 -0800
From: Reinette Chatre <reinette.chatre@...el.com>
To: James Morse <james.morse@....com>, <x86@...nel.org>,
	<linux-kernel@...r.kernel.org>
CC: 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>, Koba Ko <kobak@...dia.com>, Shanker
 Donthineni <sdonthineni@...dia.com>, Shaopeng Tan
	<tan.shaopeng@...fujitsu.com>, "Tony Luck" <tony.luck@...el.com>
Subject: Re: [PATCH v6 18/42] x86/resctrl: Move the is_mbm_*_enabled() helpers
 to asm/resctrl.h

Hi James,

On 2/7/25 10:17 AM, James Morse wrote:
> The architecture specific parts of resctrl provide helpers like
> is_mbm_total_enabled() and is_mbm_local_enabled() to hide accesses
> to the rdt_mon_features bitmap.
> 
> Exposing a group of helpers between the architecture and filesystem code
> is preferable to a single unsigned-long like rdt_mon_features. Helpers
> can be more readable and have a well defined behaviour, while allowing
> architectures to hide more complex behaviour.
> 
> Once the filesystem parts of resctrl are moved, these existing helpers can
> no longer live in internal.h. Move them to include/linux/resctrl.h
> Once these are exposed to the wider kernel, they should have a
> 'resctrl_arch_' prefix, to fit the rest of the arch<->fs interface.
> 
> Move and rename the helpers that touch rdt_mon_features directly.
> is_mbm_event() and is_mbm_enabled() are only called from rdtgroup.c,
> so can be moved into that file.
> 
> Signed-off-by: James Morse <james.morse@....com>
> Tested-by: Carl Worth <carl@...amperecomputing.com> # arm64
> Tested-by: Shaopeng Tan <tan.shaopeng@...fujitsu.com>
> Reviewed-by: Tony Luck <tony.luck@...el.com>
> ---

...

> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
> index 1730ba814834..b7d93670ed94 100644
> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c

...

> @@ -761,6 +761,9 @@ static void update_mba_bw(struct rdtgroup *rgrp, struct rdt_mon_domain *dom_mbm)
>  	struct rdtgroup *entry;
>  	u32 cur_bw, user_bw;
>  
> +	if (!resctrl_arch_is_mbm_local_enabled())
> +		return;
> +
>  	r_mba = resctrl_arch_get_resource(RDT_RESOURCE_MBA);
>  	evt_id = rgrp->mba_mbps_event;
>  

Please drop this hunk. A new [1] resctrl feature makes it possible for software
controller to work with local as well as total bandwidth events. 

Reinette

[1] https://lore.kernel.org/all/20241206163148.83828-1-tony.luck@intel.com/