On Tue, Feb 15, 2022 at 10:11:01AM +0100, Joerg Roedel wrote: > > But, then, the requirement is that nobody is using the dma API when we > > make this change? > > That is the tricky part. DMA-API keeps working after the change is made, > because the new domain is also direct mapped. The new domain just has > the ability to assign host page-tables to device PASIDs, so that DMA > requests with a PASID TLP will be remapped. From, what you've described this is also a good use case for the replace_group idea.. Using Lu's series we'd: - Require the group to be in DMA-API mode. We know this is the case because of how we got here from probe() - Use the 'replace group's domain' API to switch the group from one identity translation domain to another identity translation domain - Rely on the DMA-API refcount to block VFIO/etc instead of checking for the default domain - Restore the default domain when all the DMA-API mode drivers unprobe That is, if Robin's idea to just get the right domain in the first place doesn't work. Anyhow, given all this I think this patch is not OK as is. Thanks, Jason
