On Wed, 2 May 2018 10:31:50 +0100 Jean-Philippe Brucker <jean-philippe.bruc...@arm.com> wrote:
> 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. > Sorry for the delay but you are right, I have also confirmed with Yi that we don't need second level invalidation. I will remove IOTLB invalidation w/o PASID case from the API. Thanks, > Thanks, > Jean > [Jacob Pan]
