linux-kernel - Re: [PATCH] x86, mce: disable MCE if cpu has no MCE banks

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Message-ID: <ada8wevtpbk.fsf@cisco.com>
Date:	Wed, 28 Oct 2009 10:12:47 -0700
From:	Roland Dreier <rdreier@...co.com>
To:	Andi Kleen <ak@...ux.intel.com>
Cc:	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>,
	Mike Travis <travis@....com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
	x86@...nel.org
Subject: Re: [PATCH] x86, mce: disable MCE if cpu has no MCE banks

 > Perhaps they could be also compressed a bit like SRAT.

Seems like a good idea... but I wonder what the best way to represent
things is.  For example I have a 2-socket Nehalem system that shows:

 2 times:  MCA banks CMCI:2 CMCI:3 CMCI:5 CMCI:6 SHD:8
 6 times:  MCA banks CMCI:2 CMCI:3 CMCI:5 SHD:6 SHD:8
 8 times:  MCA banks SHD:2 SHD:3 SHD:5 SHD:6 SHD:8

presumably the first line is once per package, the next line is for the
first sibling in all the other cores in a package, and the last line is
for the SMT siblings of all the cores.

But would we want to accumulate all the different combinations of banks
along with a CPU mask and then print something like:

 CPUs 0 4: MCA banks CMCI:2 CMCI:3 CMCI:5 CMCI:6 SHD:8
 CPUs 1 2 3 5 6 7: MCA banks CMCI:2 CMCI:3 CMCI:5 SHD:6 SHD:8
 CPUs 8 9 10 11 12 13 14 15: MCA banks SHD:2 SHD:3 SHD:5 SHD:6 SHD:8

of course output like that is going to lead to super-long lines on a
64-thread system.

Also I'm not sure of a clean way to implement this; unlike the SRAT
stuff, we need to deal with CPU hotplug so all this at best could be
__cpuinitdata, ie we can't discard it in most configs.

However the "MCA banks" output definitely is annoying on a 64-thread
system -- the amount of output is far greater than the utility of said
output.  So ideas on the best way to reduce this would be appreciated.

Thanks,
  Roland
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