From mboxrd@z Thu Jan  1 00:00:00 1970
From: Gleb Natapov <gleb@redhat.com>
Subject: Re: Correct way of tracking reads on given gfn ?
Date: Mon, 9 Sep 2013 15:29:21 +0300
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Cc: SPA <infinite.questions@gmail.com>,
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To: Paolo Bonzini <pbonzini@redhat.com>
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On Mon, Sep 09, 2013 at 12:53:02PM +0200, Paolo Bonzini wrote:
> Il 09/09/2013 12:22, SPA ha scritto:
> > Thanks Paolo.
> > 
> > Is there a way where reads would trap ?
> > 
> > I explored a bit on PM_PRESENT_MASK.  Though its not READ bit, but a
> > PRESENT bit,  it looks like it should generate traps on reads if this
> > bit is reset. From code, looks like rmap_write_protect() like function
> > I stated in previous mail should do. Would this approach work ? Are
> > there any glaring problems with this approach ?
> 
> I cannot say right away.  Another way could be to set reserved bits to
> generate EPT misconfigurations.  See ept_set_mmio_spte_mask and
> is_mmio_spte.
> 
> This would trap both reads and writes.
> 
Dropping all sptes will also work, but trapping each read access will be dog slow. QEMU
emulation will be much faster.

--
			Gleb.