linux-kernel - Re: [PATCH UPDATE] x86: ignore spurious faults

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Date:	Fri, 25 Jan 2008 10:51:07 +0100
From:	Andi Kleen <ak@...ell.com>
To:	Keir Fraser <Keir.Fraser@...cam.ac.uk>
Cc:	Nick Piggin <nickpiggin@...oo.com.au>,
	Jan Beulich <jbeulich@...ell.com>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Ingo Molnar <mingo@...e.hu>,
	Harvey Harrison <harvey.harrison@...il.com>,
	Matt Mackall <mpm@...enic.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH UPDATE] x86: ignore spurious faults


> Whether this a problem in light of Xen spurious faults depends on whether
> NMI handlers touch dynamically-allocated data. And if they do, it still
> depends on the exact scenario. If it is likely to be a problem, a Xen pv_op
> can flush the TLB on NMI entry, or we could have Xen do that implicitly
> before invoking the guest NMI handler.

For PV kernels it would probably be better to just implement a truly
nesting NMI trigger method instead of the one bit state of the real hardware.

Actually I'm not sure NMIs are really that useful for guests. Most things
done traditionally by NMIs are probably better done outside the guest
in a virtualized environment.

-Andi
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