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

[Keir Fraser <keir@xxxxxxxxxxxxx>]

On 9/12/06 9:34 am, "Keir Fraser" <keir@xxxxxxxxxxxxx> wrote:

>> If _PAGE_PRESENT is clear then the other N-1 bits can be assumed available
>> for things like swapcache info. Making assumptions about not-present PTEs is
>> not really tenable.
> 
> Speaking more constructively we could have a pte_active_mask communicated
> via elfnote or xenbus (or some other way) which the tools would apply to
> PTEs to determine if they contain an MFN. Default would be 0x1.

Or we could apply the special case only for images with the OS elfnote set
to 'linux', if all Linux kernels have the same PROT_NONE definition.

With any of these solutions, the problem is how to communicate the flag or
mask to xc_linux_save/xc_linux_restore, and how to propagate it across
save/restore (i.e., how is it represented in a saved image?).

 -- Keir


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