linux-kernel - Re: [RFC PATCH] perf/x86/intel/rapl: avoid access unallocate memory

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Date:   Tue, 8 Nov 2016 15:31:35 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     "Charles (Chas) Williams" <ciwillia@...cade.com>
cc:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>, x86@...nel.org,
        linux-kernel@...r.kernel.org, "M. Vefa Bicakci" <m.v.b@...box.com>
Subject: Re: [RFC PATCH] perf/x86/intel/rapl: avoid access unallocate
 memory

On Tue, 8 Nov 2016, Charles (Chas) Williams wrote:
> 	[    0.016335] topology_update_package_map:  apicid 0  pkg 0  cpu 0
> 	[    0.016398] smpboot: APIC(0) Converting physical 0 to logical
> package 0, cpu 0 (ffff88023fc0a040)
> 	[    0.016399] topology_update_package_map:  apicid 1  pkg 1  cpu 1
> 	[    0.016462] smpboot: APIC(1) Converting physical 1 to logical
> package 1, cpu 1 (ffff88023fd0a040)
> 
> So, I don't know where apic->cpu_present_to_apicid(cpu) is getting its
> apicid but it certainly doesn't seem to the match the apicid in the
> CPU's registers.  For whatever reason, my VMware system is reporting
> that the second CPU has a local APIC ID of 2:

The initial information comes from MP tables or ACPI.
 
> 	[    0.009115] identify_cpu: cpu_index 0  phys_proc_id is now 0,
> apicid 0, initial_apicid 0
> 	...
> 	[    0.237401] identify_cpu: cpu_index 1  phys_proc_id is now 2,
> apicid 2, initial_apicid 2

And the CPUID emulation tells something different. Sigh!

> I was thinking it might be better to call topology_update_package_map()
> at the bottom of identify_cpu() to setup the secondary CPU's.  The boot
> cpu could be setup during smp_init_package_map().

Perhaps, but that does not make the inconsistencies go away....

Thanks,

	tglx