linux-kernel - Re: [PATCH] x86: UV BAU Increase maximum CPUs per socket/hub

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Message-ID: <alpine.DEB.2.11.1411012121350.5308@nanos>
Date:	Sat, 1 Nov 2014 21:23:47 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	James Custer <jcuster@....com>
cc:	x86@...nel.org, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...hat.com>,
	"H . Peter Anvin" <hpa@...or.com>, Russ Anderson <rja@....com>
Subject: Re: [PATCH] x86: UV BAU Increase maximum CPUs per socket/hub

On Fri, 31 Oct 2014, James Custer wrote:

> We have encountered hardware with 18 cores/socket that gives 36 CPUs/socket
> with hyperthreading enabled. This exceeds the current MAX_CPUS_PER_SOCKET
> causing a failure in get_cpu_topology. Increase MAX_CPUS_PER_SOCKET to 64
> and MAX_CPUS_PER_UVHUB to 128.
> 
> Additionally, this exposed another bug. When get_cpu_topology fails, we
> need to make sure that we do not use bau_control->statp (e.g. when a
> user reads /proc/sgi_uv/ptc_statistics causing ptc_seq_show to be
> invoked). In uv_bau_init we call set_bau_off() when
> init_per_cpu()->get_cpu_topology() fails -- therefore, to avoid
> referencing a NULL pointer we add code that detects when the bau is off
> and print out the bau is disabled.

Can you please split this in two patches. One fixing the ptc_seq_show
bug and the other increasing the constants. 
 
If someone looks for a fix for the ptc_seq_show wreckage he definitly
is not going to look at a patch which increases the number of cpus per
socket.

Thanks,

	tglx
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