On 01/05/18 23:58, Jacob Pan wrote: >>>> Maybe this should be called "NG_PAGE_PASID", >>> Sure. I was thinking page range already implies non-global pages. >>>> and "DOMAIN_PAGE" should >>>> instead be "PAGE_PASID". If I understood their meaning correctly, >>>> it would be more consistent with the rest. >>>> >>> I am trying not to mix granu between request w/ PASID and w/o. >>> DOMAIN_PAGE meant to be for request w/o PASID. >> >> Is the distinction necessary? I understand the IOMMU side might offer >> many possibilities for invalidation, but the user probably doesn't >> need all of them. It might be easier to document, upstream and >> maintain if we only specify what's currently needed by users (what >> does QEMU VT-d use?) Others can always extend it by increasing the >> version. >> >> Do you think that this invalidation message will be used outside of >> BIND_PASID_TABLE context? I can't see an other use but who knows. At >> the moment requests w/o PASID are managed with >> VFIO_IOMMU_MAP/UNMAP_DMA, which doesn't require invalidation. And in >> a BIND_PASID_TABLE context, IOMMUs requests w/o PASID are just a >> special case using PASID 0 (for Arm and AMD) so I suppose they'll use >> the same invalidation commands as requests w/ PASID. >> > My understanding is that for GIOVA use case, VT-d vIOMMU creates > GIOVA-GPA mapping and the host shadows the 2nd level page tables to > create GIOVA-HPA mapping. So when assigned device in the guest can do > both DMA map/unmap and VFIO map/unmap, VFIO unmap is one time deal > (I guess invalidation can be captured in other code path), but guest > kernel use of DMA unmap could will trigger invalidation. QEMU needs to > trap those invalidation and passdown to physical IOMMU. So we do need > invalidation w/o PASID.
Hm, isn't this all done by host userspace? Whether guest does DMA map/unmap or VFIO map/unmap, it creates/removes IOVA-GPA mappings in the vIOMMU. QEMU captures invalidation requests for these mappings from the guest, finds GPA-HVA in the shadow map and sends a VFIO map/unmap request for IOVA-HVA. Thanks, Jean
