Re: [PATCH v2] x86/centaur: report correct CPU/cache topology

[David Wang]

> -----Original Mail-----
> Sender: Thomas Gleixner [mailto:tglx@xxxxxxxxxxxxx]
> Time: 2018年4月26日 17:12
> Receiver: David Wang <davidwang@xxxxxxxxxxx>
> CC: mingo@xxxxxxxxxx; hpa@xxxxxxxxx; gregkh@xxxxxxxxxxxxxxxxxxx;
> x86@xxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; brucechang@via-
> alliance.com; cooperyan@xxxxxxxxxxx; qiyuanwang@xxxxxxxxxxx;
> benjaminpan@xxxxxxxxxxx; lukelin@xxxxxxxxxx; timguo@xxxxxxxxxxx
> Subject: Re: [PATCH v2] x86/centaur: report correct CPU/cache topology
> 
> On Wed, 25 Apr 2018, David Wang wrote:
> >
> > +static void early_init_centaur_mc(struct cpuinfo_x86 *c) { #ifdef
> > +CONFIG_SMP
> > +	unsigned int eax, ebx, ecx, edx;
> > +
> > +	if (c->cpuid_level < 4)
> > +		return;
> > +
> > +	cpuid_count(4, 0, &eax, &ebx, &ecx, &edx);
> > +	if (eax & 0x1f)
> > +		c->x86_max_cores = (eax >> 26) + 1;
> > +	else
> > +		return;
> > +#endif
> > +}
> 
> My review comment from last time still stands:
> 
> > > This is a bad copy of intel_num_cpu_cores(). See for the subtle
> > > difference. Please rename the intel function and move it to common.c
> 
> In other words:
> 
> Make a patch which moves intel_num_cpu_cores() into common.c. Rename
> the function into something like detect_num_cpu_cores() and fix up the
call
> site in intel.c.
> 
> Then add your patch and use the very same function.
> 

	OK. I got it.
> > +
> >  static void early_init_centaur(struct cpuinfo_x86 *c)  {
> > +	early_init_centaur_mc(c);
> >  	switch (c->x86) {
> >  #ifdef CONFIG_X86_32
> >  	case 5:
> > @@ -146,6 +163,7 @@ static void centaur_detect_vmx_virtcap(struct
> > cpuinfo_x86 *c)
> >
> >  static void init_centaur(struct cpuinfo_x86 *c)  {
> > +	unsigned int l2 = 0;
> >  #ifdef CONFIG_X86_32
> >  	char *name;
> >  	u32  fcr_set = 0;
> > @@ -161,6 +179,17 @@ static void init_centaur(struct cpuinfo_x86 *c)
> > #endif
> >  	early_init_centaur(c);
> >
> > +	l2 = init_intel_cacheinfo(c);
> > +
> > +	/* Detect legacy cache sizes if init_intel_cacheinfo did not */
> > +	if (l2 == 0) {
> > +		cpu_detect_cache_sizes(c);
> > +	}
> 
> Aside of the pointless parentheses, this really wants to be cleaned up as
well.
> 
> init_intel_cacheinfo() is called from the intel init code and it does the
same
> silly thing.
> 
> So the right thing to do is in a separate patch first
> 
> --- a/arch/x86/kernel/cpu/intel.c
> +++ b/arch/x86/kernel/cpu/intel.c
> @@ -679,12 +679,6 @@ static void init_intel(struct cpuinfo_x8
> 
>  	l2 = init_intel_cacheinfo(c);
> 
> -	/* Detect legacy cache sizes if init_intel_cacheinfo did not */
> -	if (l2 == 0) {
> -		cpu_detect_cache_sizes(c);
> -		l2 = c->x86_cache_size;
> -	}
> -
>  	if (c->cpuid_level > 9) {
>  		unsigned eax = cpuid_eax(10);
>  		/* Check for version and the number of counters */
> --- a/arch/x86/kernel/cpu/intel_cacheinfo.c
> +++ b/arch/x86/kernel/cpu/intel_cacheinfo.c
> @@ -802,6 +802,11 @@ unsigned int init_intel_cacheinfo(struct
> 
>  	c->x86_cache_size = l3 ? l3 : (l2 ? l2 : (l1i+l1d));
> 
> +	/* Detect legacy cache sizes if the above did not work */
> +	if (!l2) {
> +		cpu_detect_cache_sizes(c);
> +		l2 = c->x86_cache_size;
> +	}
>  	return l2;
>  }
> 
> Hmm?
> 
> 	tglx
> 
	OK. I got it.
	Patch v3 will be sent later.
	Thank you.
---
David