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Sender: Muli Ben-Yehuda <mulix@mulix.org>
Date: Wed, 19 Sep 2012 16:37:20 +0300
From: Muli Ben-Yehuda <muli@cs.technion.ac.il>
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Subject: Re: [Qemu-devel] Will the ELI incorporated in theKVM?
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To: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Nadav Amit <nadav.amit@gmail.com>, Nadav Har'el <nyh@il.ibm.com>, GaoYi <gaoyi709@gmail.com>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>, Abel Gordon <abelg@il.ibm.com>

On Tue, Sep 18, 2012 at 03:08:40PM +0200, Jan Kiszka wrote:
> On 2012-09-18 14:50, GaoYi wrote:
> > Hi Jan,
> > 
> >    I have followed a previous thread about ELI proposed by Abel Gordon, http://www.spinics.net/lists/kvm/msg73907.html.
> >    I wonder whether this mechanism will be incorporated in KVM someday.
> 
> Likely not. Both Intel and AMD will soon ship hardware that
> obsoletes this invasive and imperfect software solution, see also
> [1].

Hi Jan,

I think this decision may be short-sighted. First, it remains to be
seen how good the upcoming hardware support for interrupt
virtualization will be once it ships. Second, history has been pretty
consistent in that it takes several years for hardware to catch up to
software, and even when it does, software sometimes still wins. (There
are workloads where shadow page tables still outperform EPT/NPT, to
give a concrete example). Although ELI works today, I'd be happy to
hear what parts of it you find "invasive" and "imperfect" (what
software ever is perfect?)

Cheers,
Muli