[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] Does xc_map_foreign_pages() update IOMMU tables?
Does the xc_map_foreign_pages() update also the IOMMU/VT-d tables so that the mapped pages belong also to Dom0 (from the IOMMU point of view)? It seems like it does indeed. We use this function in Qubes GUI virtualization to map composition buffers from DomUs into Dom0. Then we use XShmPutImage() in Dom0 to display them. We've been told [1] that XShmPutImage() often uses DMA to copy pages to the video memory, especially in case of accelerated drivers. And we verified that our GUI works fine on VT-d systems e.g. with Intel drivers with h/w acceleration enabled and with iommu=pv enabled. This suggests that xc_map_foreign_pages() indeed must be adding mapped pages to the IOMMU tables for Dom0, as otherwise XShmPutImage() would not be able to DMA-read the contents of those pages, that originally belonged to some other DomUs. Am I missing something? If not, can somebody point me to the actual code in Xen which does this update? Thanks a lot! joanna. [1] http://groups.google.com/group/qubes-devel/msg/9d23cd9c26127ed7 Attachment:
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