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

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Message-ID: <20190617080909.GC214090@romley-ivt3.sc.intel.com>
Date:   Mon, 17 Jun 2019 01:09:09 -0700
From:   Fenghua Yu <fenghua.yu@...el.com>
To:     Borislav Petkov <bp@...en8.de>
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>, Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        Len Brown <lenb@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>
Subject: Re: [PATCH 1/3] x86/resctrl: Get max rmid and occupancy scale
 directly from CPUID instead of cpuinfo_x86

On Mon, Jun 17, 2019 at 09:52:14AM +0200, Borislav Petkov wrote:
> On Sun, Jun 16, 2019 at 08:18:09PM -0700, Fenghua Yu wrote:
> > diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
> > index 2c57fffebf9b..f080be35da41 100644
> > --- a/arch/x86/kernel/cpu/common.c
> > +++ b/arch/x86/kernel/cpu/common.c
> > @@ -801,6 +801,31 @@ static void init_speculation_control(struct cpuinfo_x86 *c)
> >  	}
> >  }
> >  
> > +static void get_cqm_info(struct cpuinfo_x86 *c)
> > +{
> > +	if (cpu_has(c, X86_FEATURE_CQM_LLC)) {
> > +		u32 eax, ebx, ecx, edx;
> > +
> > +		/* QoS sub-leaf, EAX=0Fh, ECX=0 */
> > +		cpuid_count(0x0000000F, 0, &eax, &ebx, &ecx, &edx);
> > +		/* will be overridden if occupancy monitoring exists */
> > +		c->x86_cache_max_rmid = ebx;
> > +
> > +		if (cpu_has(c, X86_FEATURE_CQM_OCCUP_LLC) ||
> > +		    cpu_has(c, X86_FEATURE_CQM_MBM_TOTAL) ||
> > +		    cpu_has(c, X86_FEATURE_CQM_MBM_LOCAL)) {
> > +			/* QoS sub-leaf, EAX=0Fh, ECX=1 */
> > +			cpuid_count(0x0000000F, 1, &eax, &ebx, &ecx, &edx);
> > +
> > +			c->x86_cache_max_rmid = ecx;
> > +			c->x86_cache_occ_scale = ebx;
> > +		}
> > +	} else {
> > +		c->x86_cache_max_rmid = -1;
> > +		c->x86_cache_occ_scale = -1;
> > +	}
> > +}
> > +
> >  void get_cpu_cap(struct cpuinfo_x86 *c)
> >  {
> >  	u32 eax, ebx, ecx, edx;
> > @@ -832,33 +857,6 @@ void get_cpu_cap(struct cpuinfo_x86 *c)
> >  		c->x86_capability[CPUID_D_1_EAX] = eax;
> >  	}
> >  
> > -	/* Additional Intel-defined flags: level 0x0000000F */
> > -	if (c->cpuid_level >= 0x0000000F) {
> > -
> > -		/* QoS sub-leaf, EAX=0Fh, ECX=0 */
> > -		cpuid_count(0x0000000F, 0, &eax, &ebx, &ecx, &edx);
> > -		c->x86_capability[CPUID_F_0_EDX] = edx;
> > -
> > -		if (cpu_has(c, X86_FEATURE_CQM_LLC)) {
> > -			/* will be overridden if occupancy monitoring exists */
> > -			c->x86_cache_max_rmid = ebx;
> > -
> > -			/* QoS sub-leaf, EAX=0Fh, ECX=1 */
> > -			cpuid_count(0x0000000F, 1, &eax, &ebx, &ecx, &edx);
> > -			c->x86_capability[CPUID_F_1_EDX] = edx;
> > -
> > -			if ((cpu_has(c, X86_FEATURE_CQM_OCCUP_LLC)) ||
> > -			      ((cpu_has(c, X86_FEATURE_CQM_MBM_TOTAL)) ||
> > -			       (cpu_has(c, X86_FEATURE_CQM_MBM_LOCAL)))) {
> > -				c->x86_cache_max_rmid = ecx;
> > -				c->x86_cache_occ_scale = ebx;
> > -			}
> > -		} else {
> > -			c->x86_cache_max_rmid = -1;
> > -			c->x86_cache_occ_scale = -1;
> > -		}
> > -	}
> 
> Why are you doing this carving out into a separate function since you're
> keeping the cpuinfo_x86 members?

I just keep the code a bit uniform around the calling area where
a few functions are called. So get_cqm_info() makes the code a bit more
readable.

        init_scattered_cpuid_features(c);
        init_speculation_control(c);
+       get_cqm_info(c);

        /*
         * Clear/Set all flags overridden by options, after probe.
         * This needs to happen each time we re-probe, which may happen
         * several times during CPU initialization.
         */
        apply_forced_caps(c);
}

Maybe not? If the function is not good, I can directly put the code here?

Thanks.

-Fenghua