linux-kernel - Re: [PATCH v5 17/40] x86/resctrl: Rewrite and move the for_each_*_rdt

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Message-ID: <441b7021-a423-4689-8330-c6675c4ece60@intel.com>
Date: Wed, 23 Oct 2024 14:51:25 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: James Morse <james.morse@....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 17/40] x86/resctrl: Rewrite and move the
 for_each_*_rdt_resource() walkers

Hi James,

On 10/4/24 11:03 AM, James Morse wrote:
> The for_each_*_rdt_resource() helpers walk the architecture's array
> of structures, using the resctrl visible part as an iterator. These
> became over-complex when the structures were split into a
> filesystem and architecture-specific struct. This approach avoided
> the need to touch every call site, and was done before there was a
> helper to retrieve a resource by rid.
> 
> Once the filesystem parts of resctrl are moved to /fs/, both the
> architecture's resource array, and the definition of those structures
> is no longer accessible. To support resctrl, each architecture would
> have to provide equally complex macros.
> 
> Rewrite the macro to make use of resctrl_arch_get_resource(), and
> move these to the core header so existing x86 arch code continues
> to use them.

The last part is not clear, why does it need to be moved to core
header for x86 to use it?


...

> diff --git a/include/linux/resctrl.h b/include/linux/resctrl.h
> index 8894aed3c593..f75f0409ae09 100644
> --- a/include/linux/resctrl.h
> +++ b/include/linux/resctrl.h
> @@ -26,6 +26,24 @@ int proc_resctrl_show(struct seq_file *m,
>  /* max value for struct rdt_domain's mbps_val */
>  #define MBA_MAX_MBPS   U32_MAX
>  
> +/* Walk all possible resources, with variants for only controls or monitors. */
> +#define for_each_rdt_resource(_r)						\
> +	for ((_r) = resctrl_arch_get_resource(0);				\
> +	     (_r)->rid < RDT_NUM_RESOURCES - 1;					\

I do not think this reaches all resources ... should this perhaps be:
	(_r) && (_r)->rid < RDT_NUM_RESOURCES

> +	     (_r) = resctrl_arch_get_resource((_r)->rid + 1))
> +
> +#define for_each_capable_rdt_resource(r)				      \
> +	for_each_rdt_resource((r))					      \
> +		if ((r)->alloc_capable || (r)->mon_capable)
> +
> +#define for_each_alloc_capable_rdt_resource(r)				      \
> +	for_each_rdt_resource((r))					      \
> +		if ((r)->alloc_capable)
> +
> +#define for_each_mon_capable_rdt_resource(r)				      \
> +	for_each_rdt_resource((r))					      \
> +		if ((r)->mon_capable)
> +
>  /**
>   * enum resctrl_conf_type - The type of configuration.
>   * @CDP_NONE:	No prioritisation, both code and data are controlled or monitored.

Reinette