linux-kernel - Re: [PATCH 03/11] x86 topology: Add CPUID.1F multi-die/package support

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Message-ID: <3ac80787-f282-ce94-77dc-f0e6ea9d4431@inria.fr>
Date:   Sun, 24 Feb 2019 11:04:26 +0100
From:   Brice Goglin <Brice.Goglin@...ia.fr>
To:     Len Brown <lenb@...nel.org>, x86@...nel.org
Cc:     linux-kernel@...r.kernel.org, Len Brown <len.brown@...el.com>,
        linux-doc@...r.kernel.org, Like Xu <like.xu@...ux.intel.com>
Subject: Re: [PATCH 03/11] x86 topology: Add CPUID.1F multi-die/package
 support

Le 19/02/2019 à 04:40, Len Brown a écrit :
> diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
> index ccd1f2a8e557..4250a87f57db 100644
> --- a/arch/x86/kernel/smpboot.c
> +++ b/arch/x86/kernel/smpboot.c
> @@ -393,6 +393,7 @@ static bool match_smt(struct cpuinfo_x86 *c, struct cpuinfo_x86 *o)
>  		int cpu1 = c->cpu_index, cpu2 = o->cpu_index;
>  
>  		if (c->phys_proc_id == o->phys_proc_id &&
> +		    c->cpu_die_id == o->cpu_die_id &&
>  		    per_cpu(cpu_llc_id, cpu1) == per_cpu(cpu_llc_id, cpu2)) {
>  			if (c->cpu_core_id == o->cpu_core_id)
>  				return topology_sane(c, o, "smt");
> @@ -404,6 +405,7 @@ static bool match_smt(struct cpuinfo_x86 *c, struct cpuinfo_x86 *o)
>  		}
>  
>  	} else if (c->phys_proc_id == o->phys_proc_id &&
> +		   c->cpu_die_id == o->cpu_die_id &&
>  		   c->cpu_core_id == o->cpu_core_id) {
>  		return topology_sane(c, o, "smt");
>  	}
> @@ -461,7 +463,7 @@ static bool match_llc(struct cpuinfo_x86 *c, struct cpuinfo_x86 *o)
>   */
>  static bool match_die(struct cpuinfo_x86 *c, struct cpuinfo_x86 *o)
>  {
> -	if (c->phys_proc_id == o->phys_proc_id)
> +	if (c->cpu_die_id == o->cpu_die_id)
>  		return true;
>  	return false;
>  }

Hello Len,

I am testing your patches in a VM with CPUID.1f QEMU patches (author Like Xu is CC'ed),
booted to get 2 packages with 1 NUMA node each and 2 dies each:

-smp cpus=16,threads=2,cores=2,dies=2,sockets=2 -numa node,cpus=0-7,nodeid=0 -numa node,cpus=8-15,nodeid=1

sysfs files expose wrong information:
core_siblings contains threads of the local die AND of die with same number in other processors,
eg cpu 0-3 and 8-11 instead of 0-3 only.

The issue is that you seem to assume that die ids will always be unique across multiple packages.
Is this a valid assumption? If so, QEMU patches should be fixed.
If not, I fixed the issue by changing match_die() to check both phys_proc_id and cpu_die_id:

static bool match_die(struct cpuinfo_x86 *c, struct cpuinfo_x86 *o)
{
	if (c->phys_proc_id == o->phys_proc_id && c->cpu_die_id == o->cpu_die_id)
 		return true;
	return false;
}

Thanks
Brice