linux-kernel - Re: [PATCH v4 07/39] x86/resctrl: Add max_bw to struct resctrl

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Message-ID: <ca528ebd-fb76-40cd-a495-88c2de443cd8@intel.com>
Date: Tue, 13 Aug 2024 21:00:23 -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>
Subject: Re: [PATCH v4 07/39] x86/resctrl: Add max_bw to struct resctrl_membw

Hi James,

On 8/2/24 10:28 AM, James Morse wrote:
> __rdt_get_mem_config_amd() and __get_mem_config_intel() both use
> the default_ctrl property as a maximum value. This is because the
> MBA schema works differently between these platforms. Doing this
> complicates determining whether the default_ctrl property belongs
> to the arch code, or can be derived from the schema format.
> 
> Add a max_bw property for AMD platforms to specify their maximum

"for AMD platforms" -> "for x86 platforms"?

> MBA bandwidth. This isn't needed for other schema formats.
> 
> This will allow the default_ctrl to be generated from the schema
> properties when it is needed.
> 
> Signed-off-by: James Morse <james.morse@....com>
> Tested-by: Carl Worth <carl@...amperecomputing.com> # arm64

...

> @@ -108,8 +108,9 @@ static int parse_bw(struct rdt_parse_data *data, struct resctrl_schema *s,
>    */
>   static bool cbm_validate(char *buf, u32 *data, struct rdt_resource *r)
>   {
> -	unsigned long first_bit, zero_bit, val;
> +	u32 supported_bits = BIT_MASK(r->cache.cbm_len + 1) - 1;

hmmm ... should this be:
	u32 supported_bits = BIT_MASK(r->cache.cbm_len) - 1;

Reinette