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Message-ID: <1339521493.31548.93.camel@twins>
Subject: Re: [PATCH] perf/x86: check ucode before disabling PEBS on
 SandyBridge
From: Peter Zijlstra <peterz@infradead.org>
To: Borislav Petkov <bp@amd64.org>
Cc: Stephane Eranian <eranian@google.com>,
        Robert Richter <robert.richter@amd.com>,
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        Andreas Herrmann <andreas.herrmann3@amd.com>,
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        Dmitry Adamushko <dmitry.adamushko@gmail.com>
Date: Tue, 12 Jun 2012 19:18:13 +0200
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On Tue, 2012-06-12 at 19:17 +0200, Borislav Petkov wrote:
> On Tue, Jun 12, 2012 at 07:13:23PM +0200, Peter Zijlstra wrote:
> > > That's what I had in my original version.
> > 
> > Right, but you really need to check all cpus, not just the one you
> > happen to run on or the boot cpu.
> 
> Ok, the answer to that question is whether sandybridge can support mixed
> ucode revisions or not. If not, you only need to check the current cpu
> you're on.

But the ucode loader can be (ab)used to only update one of the many
CPUs.