Date:   Tue, 21 Feb 2023 10:00:54 +0100
From:   Peter Zijlstra <peterz@infradead.org>
To:     Thomas Gleixner <tglx@linutronix.de>
Cc:     "Zhang, Rui" <rui.zhang@intel.com>,
        "Brown, Len" <len.brown@intel.com>,
        "zhang.jia@linux.alibaba.com" <zhang.jia@linux.alibaba.com>,
        "bp@alien8.de" <bp@alien8.de>,
        "dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
        "hpa@zytor.com" <hpa@zytor.com>,
        "mingo@redhat.com" <mingo@redhat.com>,
        "x86@kernel.org" <x86@kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH V2 0/1] x86: cpu topology fix and question on
 x86_max_cores
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References: <20230220032856.661884-1-rui.zhang@intel.com>
 <Y/NUni00nDuURT1H@hirez.programming.kicks-ass.net>
 <fe5059317c4f3cabeb86c388d547504b9b6ea581.camel@intel.com>
 <87edqkosty.ffs@tglx>
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On Mon, Feb 20, 2023 at 11:49:45PM +0100, Thomas Gleixner wrote:

> > I thought of improving this by parsing all the valid APIC-IDs in MADT
> > during BSP bootup, and get such information by decoding the APIC-IDs
> > using the APIC-ID layout information retrieved from BSP. But this is
> > likely to be a fertile new source of bugs as Dave concerned.
> 
> The APIC-IDs are only usefull if there is an architected scheme how they
> are assigned. Is there such a thing?

Isn't that given through CPUID? Or are we worried each CPU will have
different values in the topology leafs?

We really should have added that CPUID uniformity sanity check a long
while ago :-(