Re: [PATCH 1/3] x86/resctrl: Get max rmid and occupancy scale directly from CPUID instead of cpuinfo_x86

[Fenghua Yu]

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