On Sun, May 12, 2024 at 11:46:54AM -0300, Jason Gunthorpe wrote: > On Fri, Apr 12, 2024 at 08:47:04PM -0700, Nicolin Chen wrote: > > Add a pair of ops to set and unet device's virtual ID that belongs to > > a viommu object. They will be used, in the following patch, by iommufd > > to support some HW-acceleration feature from the host level. > > > > For instance, every device behind an ARM SMMU has a Stream ID. The ID > > is used by ATC invalidation commands so SMMU HW can direct invalidation > > requests to the corresponding PCI device where the ID belongs to. In a > > virtualization use case, a passthroughed device in the VM will have a > > virtuail Stream ID, used by the ATC invalidation commands in the guest > > system. NVIDIA's CMDQV extension for SMMUv3 provides a v-interface to > > execute the guest-level ATC invalidation commands directly, yet needs > > the HW to be aware of its virtual Stream ID so it can replace with its > > physical Stream ID. > > I imagine using this as well for the ATC invalidation commands. It > would be very easy and simplifying if the command fixup just extracted > the vSID from the ATC invalidation and used an xarray to turn it into > a pSID and then pushed the resulting command. You mean the nested SMMU series right? Actually the set_dev_id ioctl was a part of that until we wanted to try DEV_INVALIDATE. So again, yes, it makes sense to me that we move viommu and the set_dev_id to the nested series, and then drop DEV_INVALIDATE. Thanks Nicolin
