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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