On Wed, Feb 19, 2020 at 11:40 AM Lu Baolu <[email protected]> wrote: > With respect, this is problematical. The parent and all subdevices share > a single translation entry. The DMA mask should be consistent. > > Otherwise, for example, subdevice A has 64-bit DMA capability and uses > an identity domain for DMA translation. While subdevice B has 32-bit DMA > capability and is forced to switch to DMA domain. Subdevice A will be > impacted without any notification.
I see what you mean. Perhaps we should just ensure that setups involving such real DMA devices and subdevices should always use the DMA domain, avoiding this type of complication. That's apparently even the default for VMD. This is probably something that should be forced/ensured when the real DMA device gets registered, because similarly to the noted case, we can't risk any identity mappings having been created on the real device if we later decide to move it into the DMA domain based on the appearance of subdevices. Jon, any thoughts? Daniel _______________________________________________ iommu mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/iommu
