From: Jason Gunthorpe jgg@nvidia.com Sent: Tuesday, October 22, 2024 9:16 PM
On Tue, Oct 22, 2024 at 04:59:07PM +0800, Baolu Lu wrote:
Is it feasible to make vIOMMU object more generic, rather than strictly tying it to nested translation? For example, a normal paging domain that translates gPAs to hPAs could also have a vIOMMU object associated with it.
While we can only support vIOMMU object allocation uAPI for S2 paging domains in the context of this series, we could consider leaving the option open to associate a vIOMMU object with other normal paging domains that are not a nested parent?
Why? The nested parent flavour of the domain is basically free to create, what reason would be to not do that?
If the HW doesn't support it, then does the HW really need/support a VIOMMU?
Now it's agreed to build trusted I/O on top of this new vIOMMU object. format-wise probably it's free to assume that nested parent is supported on any new platform which will support trusted I/O. But I'm not sure all the conditions around allowing nested are same as for trusted I/O, e.g. for ARM nesting is allowed only for CANWBS/S2FWB. Are they always guaranteed in trusted I/O configuration?
Baolu did raise a good open to confirm given it will be used beyond nesting. 😊