linux-kernel - Re: [tip:perf/core] perf/x86: Fix USER/KERNEL tagging of samples

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Message-ID: <1341910360.3462.99.camel@twins>
Date:	Tue, 10 Jul 2012 10:52:40 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>, hpa@...or.com,
	eranian@...gle.com, linux-kernel@...r.kernel.org,
	fweisbec@...il.com, akpm@...ux-foundation.org, tglx@...utronix.de,
	linux-tip-commits@...r.kernel.org,
	Robert Richter <robert.richter@....com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Jeremy Fitzhardinge <jeremy@...p.org>
Subject: Re: [tip:perf/core] perf/x86: Fix USER/KERNEL tagging of samples

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..
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