Re: [Xen-devel] Re: Next steps with pv_ops for Xen

[Derek Murray <Derek.Murray@xxxxxxxxxxxx>]

Keir Fraser wrote:
> Need to bite the bullet and fix this properly by setting a software flag in
> ptes that are not subject to reference counting.
Could we get away with testing the VM_FOREIGN flag in vm_normal_page()? 
Although I get the impression that this wouldn't be easily justified if 
trying to merge with upstream Linux....
> Unfortunately that also needs a hypervisor interface change, to allow
> setting of those pte flags. Easily done though, and we should definitely get
> that piece in for 3.2.0.
Alternatively, could we use the _PAGE_GNTTAB PTE flag that is used for 
debugging? Indeed, if we did this, could be obviate the need for the 
PTE-zapping hook, by instead catching the case where this flag is set, 
and unmapping the grant implicitly?
Otherwise, what would the semantics of this new flag be?

Regards,

Derek.

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