linux-kernel - Re: [RFC PATCH 06/10] arch/x86: Initialize the resource functions that are different

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Message-ID: <d35e76c8-a79a-c574-33ff-20db12b8219a@intel.com>
Date:   Tue, 2 Oct 2018 15:06:15 -0700
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     "Moger, Babu" <Babu.Moger@....com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "hpa@...or.com" <hpa@...or.com>,
        "fenghua.yu@...el.com" <fenghua.yu@...el.com>,
        "vikas.shivappa@...ux.intel.com" <vikas.shivappa@...ux.intel.com>,
        "tony.luck@...el.com" <tony.luck@...el.com>
Cc:     "x86@...nel.org" <x86@...nel.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "pombredanne@...b.com" <pombredanne@...b.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "kstewart@...uxfoundation.org" <kstewart@...uxfoundation.org>,
        "bp@...e.de" <bp@...e.de>,
        "rafael.j.wysocki@...el.com" <rafael.j.wysocki@...el.com>,
        "ak@...ux.intel.com" <ak@...ux.intel.com>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
        "xiaochen.shen@...el.com" <xiaochen.shen@...el.com>,
        "colin.king@...onical.com" <colin.king@...onical.com>,
        "Hurwitz, Sherry" <sherry.hurwitz@....com>,
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        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 06/10] arch/x86: Initialize the resource functions
 that are different

Hi Babu,

On 9/24/2018 12:19 PM, Moger, Babu wrote:
> Initialize the resource functions that are different between the
> vendors. Some features are initialized differently between the vendors.
> 
> For example, MBA feature varies significantly between Intel and AMD.
> Separate the initialization of these resource functions. That way we
> can easily add AMD's functions later.
> 
> Signed-off-by: Babu Moger <babu.moger@....com>
> ---
>  arch/x86/kernel/cpu/rdt.c | 28 +++++++++++++++++++++++++---
>  arch/x86/kernel/cpu/rdt.h |  4 ++++
>  2 files changed, 29 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/rdt.c b/arch/x86/kernel/cpu/rdt.c
> index 736715b81fd8..6dec45bf81d6 100644
> --- a/arch/x86/kernel/cpu/rdt.c
> +++ b/arch/x86/kernel/cpu/rdt.c
> @@ -174,10 +174,7 @@ struct rdt_resource rdt_resources_all[] = {
>  		.rid			= RDT_RESOURCE_MBA,
>  		.name			= "MB",
>  		.domains		= domain_init(RDT_RESOURCE_MBA),
> -		.msr_base		= IA32_MBA_THRTL_BASE,
> -		.msr_update		= mba_wrmsr,
>  		.cache_level		= 3,
> -		.parse_ctrlval		= parse_bw,
>  		.format_str		= "%d=%*u",
>  		.fflags			= RFTYPE_RES_MB,
>  	},
> @@ -865,6 +862,25 @@ static __init void rdt_check_mba(void)
>  		rdt_get_mem_config(&rdt_resources_all[RDT_RESOURCE_MBA]);
>  }
>  
> +static __init void rdt_init_res_defs_intel(void)
> +{
> +	struct rdt_resource *r;
> +
> +	for_each_rdt_resource(r) {
> +		if (r->rid == RDT_RESOURCE_MBA) {
> +			r->msr_base = IA32_MBA_THRTL_BASE;
> +			r->msr_update = mba_wrmsr;
> +			r->parse_ctrlval = parse_bw;
> +		}
> +	}
> +}

Patch 10 introduces parse_bw_amd and mba_wrmsr_amd as you prepare us for
in the commit message. I think it would reduce confusion if these
functions, mba_wrmsr and parse_bw, also follow this pattern to contain
the vendor name. So, mba_wrmsr -> mba_wrmsr_intel, parse_bw ->
parse_bw_intel.

> +
> +static __init void rdt_init_res_defs(void)
> +{
> +	if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL)
> +		rdt_init_res_defs_intel();
> +}
> +
>  static enum cpuhp_state rdt_online;
>  
>  static int __init rdt_late_init(void)
> @@ -875,6 +891,12 @@ static int __init rdt_late_init(void)
>  	/* Run quirks first */
>  	rdt_quirks();
>  
> +	/*
> +	 * Initialize functions(or definitions) that are different
> +	 * between vendors here.
> +	 */
> +	rdt_init_res_defs();
> +

While it does seem as though currently rdt_quirks() is not using any of
the settings made in rdt_init_res_defs() it (rdt_quirks()) does use the
partially initialized resources structure and this may in the future
include using parameters that have not been initialized yet.

I thus think it would be safer to do this initialization before
rdt_quirks().

Reinette