From mboxrd@z Thu Jan  1 00:00:00 1970
From: Joe Bonasera <joe.bonasera@sun.com>
Subject: Re: Live migration leaves page tables read-only?
Date: Mon, 11 Dec 2006 13:30:13 -0800
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To: Ian Pratt <m+Ian.Pratt@cl.cam.ac.uk>
Cc: Christian Limpach <Christian.Limpach@xensource.com>, xen-devel <xen-devel@lists.xensource.com>, John Byrne <john.l.byrne@hp.com>
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Ian Pratt wrote:
>  
>> Solaris implements PROT_NONE by entirely invalidating the PTE (ie. it
>> becomes zero). Hence our PTEs always had either zero or have the
> PRESENT
>> bit set.  The only exception to this was adding some fixage to allow
>> for the old Xen writable page table approach which temporarily made
>> the upper table non-PRESENT.
>>
>> So you can make not-present, but non-zero entries mean anything you
> want.
>> As long as it's the guest OS that creates the entries, we'll just not
> do
>> it.
> 
> Just to be confirm: in Solaris there are no not-present PTE's that
> contain machine addresses.


yes

> This means we need to implement the scheme that Keir suggested to enable
> the guest OS to tell xen/xc_save/restore about flags in not-present PTEs
> that should trigger a m2p conversion.
> 
> Ian