linux-kernel - Re: [PATCH] KVM: Veirfy memory slot only for readability

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Message-ID: <1323019756.3256.1.camel@lappy>
Date:	Sun, 04 Dec 2011 19:29:16 +0200
From:	Sasha Levin <levinsasha928@...il.com>
To:	Avi Kivity <avi@...hat.com>
Cc:	Takuya Yoshikawa <yoshikawa.takuya@....ntt.co.jp>,
	linux-kernel@...r.kernel.org,
	Marcelo Tosatti <mtosatti@...hat.com>, kvm@...r.kernel.org,
	Takuya Yoshikawa <takuya.yoshikawa@...il.com>
Subject: Re: [PATCH] KVM: Veirfy memory slot only for readability

On Sun, 2011-12-04 at 18:53 +0200, Avi Kivity wrote:
> On 12/02/2011 07:46 AM, Sasha Levin wrote:
> > > Do you want to create read only memory slots for kvm tool?
> >
> > What KVM tool currently does is copy the kernel into guest memory and
> > run it from there. An idea raised recently was instead of copying it we
> > should mmap it into the memory to reduce footprint.
> >
> > This is why I'm looking into adding a read only memory slot. The KVM
> > code doesn't have to know it's read only.
> 
> The kernel will patch itself very early.  You need to use MAP_PRIVATE
> (and thus have a read/write area).  It will be interesting to see what
> fraction of the memory is modified.
> 
> Note that mapping will remove benefits like huge page support, and that
> you can get page sharing by using ksm.  Still, it's interesting to see
> where this goes.

Why would I lose hugepage if the kernel gets it's own memory slot?

-- 

Sasha.

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