[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] Vanilla Linux and has_foreign_mapping
On Apr 29, 2008, at 1:32 PM, Jeremy Fitzhardinge wrote: 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? Good point. This extra work can happen later in the vma's callback.By removing/restoring the physical backing, I mean doing the work in balloon.c. Removing the physical backing is done by doing a XENMEM_decrease_reservation hypercall, while restoring the physical backing is done through XENMEM_populate_physmap. 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. I don't think there's a need for this, either in the current gntdev/ blktap and my work. The generic xen code can undo the user-space grant, and the vma callback can later do any extra work. Cheers, Mike _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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