On Mon, Aug 12, 2024 at 05:03:37PM +0800, Yi Liu wrote: > > The PASID may require ATS to be enabled (ie SVA), but the RID may be > > IDENTITY for performance. The poor device has no idea it is not > > allowed to use ATS on the RID side :( > > If this is the only problematic case, the intel iommu driver in this > patch could check the scalable mode before enabling ATS in the > probe_device() op. In this way, the legacy mode iommu would keep the old > ATS enable policy. At some point we will need to address this.. At least when we add PASID support to mlx5 it will need something since mlx5 is using ATS on the RID right now. Supporting ATS with the IDENTITY optimization is a good idea in the IOMMU HW. The HW just has to answer the ATS with a 1:1 TA. Next, telling the driver that ATS is enabled but doesn't work on the RID would allow the driver to deal with it Finally, doing things like using IDENTITY through a paging domain would be a last resort for troubled devices. Jason
