Re: [Xen-devel] Live migration leaves page tables read-only?

[Joe Bonasera <joe.bonasera@xxxxxxx>]

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 

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