linux-kernel - Re: [PATCH 1/3] x86/resctrl: Get max rmid and occupancy scale directly from CPUID instead of cpuinfo

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Date:   Sun, 16 Jun 2019 19:52:33 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Fenghua Yu <fenghua.yu@...el.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, H Peter Anvin <hpa@...or.com>,
        Christopherson Sean J <sean.j.christopherson@...el.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krcmar <rkrcmar@...hat.com>,
        Ravi V Shankar <ravi.v.shankar@...el.com>,
        linux-kernel <linux-kernel@...r.kernel.org>, x86 <x86@...nel.org>
Subject: Re: [PATCH 1/3] x86/resctrl: Get max rmid and occupancy scale
 directly from CPUID instead of cpuinfo_x86

On Sun, Jun 16, 2019 at 10:14:08AM -0700, Fenghua Yu wrote:
> @@ -617,13 +617,20 @@ static void l3_mon_evt_init(struct rdt_resource *r)
>  		list_add_tail(&mbm_local_event.list, &r->evt_list);
>  }
>  
> -int rdt_get_mon_l3_config(struct rdt_resource *r)
> +int __init rdt_get_mon_l3_config(struct rdt_resource *r)
>  {
>  	unsigned int cl_size = boot_cpu_data.x86_cache_size;
> +	u32 eax, ebx, ecx, edx;
>  	int ret;
>  
> -	r->mon_scale = boot_cpu_data.x86_cache_occ_scale;
> -	r->num_rmid = boot_cpu_data.x86_cache_max_rmid + 1;
> +	/*
> +	 * At this point, CQM LLC and one of L3 occupancy, MBM total, and
> +	 * MBM local monitoring features must be supported. So sub-leaf
> +	 * (EAX=0xf, ECX=1) contains needed information for this resource.
> +	 */
> +	cpuid_count(0xf, 1, &eax, &ebx, &ecx, &edx);
> +	r->num_rmid = ecx + 1;
> +	r->mon_scale = ebx;
>  
>  	/*
>  	 * A reasonable upper limit on the max threshold is the number

This is simpler than that:

https://lkml.kernel.org/r/20190614174959.GF198207@romley-ivt3.sc.intel.com

Why?


-- 
Regards/Gruss,
    Boris.

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