Re: [PATCH RFC v2 02/11] iommu: Add iommu_group_singleton_lockdown()

[Lu Baolu]

On 2022/3/30 19:58, Jason Gunthorpe wrote:
> > > Testing the group size is inherently the wrong test to make.
> > What is your suggestion then?
> Add a flag to the group that positively indicates the group can never
> have more than one member, even after hot plug. eg because it is
> impossible due to ACS, or lack of bridges, and so on.

The check method seems to be bus specific. For platform devices, perhaps
this kind of information should be retrieved from firmware interfaces
like APCI or DT.

From this point of view, would it be simpler and more reasonable for the
device driver to do such check? After all, it is the device driver that
decides whether to provide SVA services to the application via uacce.

Best regards,
baolu