Re: [Xen-devel] Vanilla Linux and has_foreign_mapping

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

Michael Abd-El-Malek wrote:
> Some drivers may need to do additional tasks besides just clearing the 
> PTE.   For example, when unzapping my kernel PTE, I need to restore 
> the physical mapping of the page.  (On the initial set_pte (which I've 
> overridden), I removed the physical backing of the page.)
> If we really want to avoid a zap_pte hook, I suppose we can add flags 
> to the page/PTE that indicate things like "this page needs to have its 
> physical backing restored".
Is that something that needs to happen synchronously with the unmap, or 
could the driver do it in its vma callback?  What do you mean by 
remove/restoring the physical backing?  Do any of the in-tree drivers do 
this?
In the PAE case, which I think we can regard as usual these days, we 
have 64-bits to store per-mapping info, so stashing a callback or 
callback index seems pretty straightforward if we need full generality.
   J

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