linux-kernel - Re: [PATCH] perf/x86: check ucode before disabling PEBS on SandyBridge

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Message-ID: <20120612172352.GA4802@aftab.osrc.amd.com>
Date:	Tue, 12 Jun 2012 19:23:52 +0200
From:	Borislav Petkov <bp@...64.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Borislav Petkov <bp@...64.org>,
	Stephane Eranian <eranian@...gle.com>,
	Robert Richter <robert.richter@....com>,
	Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
	andi@...stfloor.org, mingo@...e.hu, ming.m.lin@...el.com,
	Andreas Herrmann <andreas.herrmann3@....com>,
	Dimitri Sivanich <sivanich@....com>,
	Dmitry Adamushko <dmitry.adamushko@...il.com>
Subject: Re: [PATCH] perf/x86: check ucode before disabling PEBS on
 SandyBridge

On Tue, Jun 12, 2012 at 07:18:13PM +0200, Peter Zijlstra wrote:
> But the ucode loader can be (ab)used to only update one of the many
> CPUs.

Not if you don't support mixed ucode revisions. In that case, you want
the same ucode patch applied to _all_ cores on the system. Otherwise,
random freezes, explosions and other cataclysmic events can happen.

-- 
Regards/Gruss,
Boris.

Advanced Micro Devices GmbH
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