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Subject: Re: [tip:perf/core] perf/x86: Fix USER/KERNEL tagging of samples
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Ingo Molnar <mingo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>, hpa@zytor.com,
        eranian@google.com, linux-kernel@vger.kernel.org, fweisbec@gmail.com,
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        linux-tip-commits@vger.kernel.org,
        Robert Richter <robert.richter@amd.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        Jeremy Fitzhardinge <jeremy@goop.org>
Date: Tue, 10 Jul 2012 10:52:40 +0200
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On Tue, 2012-07-10 at 10:21 +0200, Ingo Molnar wrote:
> Another boundary condition would be when we intentionally 
> twiddle the GDT: such as during suspend or during BIOS upcalls. 
> Can we then get a PMU interrupt? If yes then this will probably 
> result in garbage:
> 
> > > > +             desc = __this_cpu_ptr(&gdt_page.gdt[0]);
> 
> it won't outright crash, we don't ever deallocate our GDT - but 
> it will return a garbage RIP.

Nothing we can do about that though..

> Then there's also all the Xen craziness with segments ...

I don't think Xen Dom0 has PMU access, that would be their Hyper-visor
thingy's job, no?

Anyway, that seems a problem for Jeremy and Konrad..