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Date: Mon, 21 Mar 2016 09:21:29 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Huang Rui <ray.huang@amd.com>
Cc: Borislav Petkov <bp@alien8.de>, Sherry Hurwitz <sherry.hurwitz@amd.com>,
        tglx@linutronix.de, linux-kernel@vger.kernel.org, mingo@kernel.org,
        aherrmann@suse.com, jencce.kernel@gmail.com,
        Gang Long <gang.long@amd.com>
Subject: Re: [PATCH 2/3] x86/topology: Fix AMD core count
Message-ID: <20160321082129.GP6344@twins.programming.kicks-ass.net>
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 <20160321030744.GA26269@hr-amur2>
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On Mon, Mar 21, 2016 at 11:07:46AM +0800, Huang Rui wrote:
> > > The issue is that Linux assumes:
> > > 
> > > 	nr_logical_cpus = nr_cores * nr_siblings
> > > 
> > > But AMD reports its CU unit as 2 cores, but then sets num_smp_siblings
> > > to 2 as well.

> But I am confused with c->x86_max_cores /= smp_num_siblings, what is
> the real meaning of c->x86_max_cores here for AMD, the whole compute
> unit numbers per socket?

Yes, with the whole Compute Unit being the Core, each logical CPU
becomes a Thread. This is the direct consequence of using the SMT
topology to model the CU thing.