On 21/4/08 19:17, "Michael Abd-El-Malek" <mabd...@cmu.edu> wrote:

I'm not really familiar with the pv_ops code I'm afraid. But thinking about this some more I've realised there's no way really to avoid making the early-unpin logic aware of gntdev mappings. This is because if we do pin pte pages, and require them to remain pinned across early-unpin, then pgd_unpin() must not attempt to make those pte pages writable. That will fail, because the pages are still pinned! You'd either need to handle the failure to make the page writable, or have a per-page flag to indicate which pte pages contain gntdev mappings. Frankly you may as well stick with the per-mm-context has_foreign_mappings flag.

Is it a pain to add a pv_ops-subtype-specific flag to mm_context? If so you could maintain a set datastructure instead, indicating which mm_contexts contain foreign mappings.

-- Keir