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Date: Mon, 20 Aug 2018 15:59:54 -0700
From: Dave Hansen <dave.hansen@...el.com>
To: Tycho Andersen <tycho@...ho.ws>,
 Linus Torvalds <torvalds@...ux-foundation.org>
Cc: David Woodhouse <dwmw@...zon.co.uk>,
 Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>, juerg.haefliger@....com,
 deepa.srinivasan@...cle.com, Jim Mattson <jmattson@...gle.com>,
 Andrew Cooper <andrew.cooper3@...rix.com>,
 Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
 Boris Ostrovsky <boris.ostrovsky@...cle.com>, linux-mm <linux-mm@...ck.org>,
 Thomas Gleixner <tglx@...utronix.de>, joao.m.martins@...cle.com,
 pradeep.vincent@...cle.com, Andi Kleen <ak@...ux.intel.com>,
 Khalid Aziz <khalid.aziz@...cle.com>, kanth.ghatraju@...cle.com,
 Liran Alon <liran.alon@...cle.com>, Kees Cook <keescook@...gle.com>,
 jsteckli@...inf.tu-dresden.de,
 Kernel Hardening <kernel-hardening@...ts.openwall.com>,
 chris.hyser@...cle.com, Tyler Hicks <tyhicks@...onical.com>,
 John Haxby <john.haxby@...cle.com>, Jon Masters <jcm@...hat.com>
Subject: Re: Redoing eXclusive Page Frame Ownership (XPFO) with isolated CPUs
 in mind (for KVM to isolate its guests per CPU)

On 08/20/2018 03:35 PM, Tycho Andersen wrote:
> Since meltdown hit, I haven't worked seriously on understand and
> implementing his suggestions, in part because it wasn't clear to me
> what pieces of the infrastructure we might be able to re-use. Someone
> who knows more about mm/ might be able to suggest an approach, though

Unfortunately, I'm not sure there's much of KPTI we can reuse.  KPTI
still has a very static kernel map (well, two static kernel maps) and
XPFO really needs a much more dynamic map.

We do have a bit of infrastructure now to do TLB flushes near the kernel
exit point, but it's entirely for the user address space, which isn't
affected by XPFO.

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