Hi, Jason On Tue, 27 Aug 2024 at 23:51, Jason Gunthorpe <jgg@xxxxxxxxxx> wrote: > > This brings support for the IOMMFD ioctls: > > - IOMMU_GET_HW_INFO > - IOMMU_HWPT_ALLOC_NEST_PARENT > - IOMMU_DOMAIN_NESTED > - ops->enforce_cache_coherency() > > This is quite straightforward as the nested STE can just be built in the > special NESTED domain op and fed through the generic update machinery. > > The design allows the user provided STE fragment to control several > aspects of the translation, including putting the STE into a "virtual > bypass" or a aborting state. This duplicates functionality available by > other means, but it allows trivially preserving the VMID in the STE as we > eventually move towards the VIOMMU owning the VMID. > > Nesting support requires the system to either support S2FWB or the > stronger CANWBS ACPI flag. This is to ensure the VM cannot bypass the > cache and view incoherent data, currently VFIO lacks any cache flushing > that would make this safe. What if the system does not support S2FWB or CANWBS, any workaround to passthrough? Currently I am testing nesting by ignoring this check. Thanks
