Re: [PATCH v10 04/12] iommu: Add attach/detach_dev_pasid iommu interface

[Baolu Lu]

On 2022/7/28 10:44, Baolu Lu wrote:
> > If the fabric routes PASID properly then groups are not an issue - all
> > agree on this?
>
> I still think the singleton group is required, but it's not related to
> the PCI fabric routing discussed here.
>
> We have a single array for PASIDs in the iommu group. All devices
> sitting in the group should share a single PASID namespace. However both
> the translation structures for IOMMU hardware or the device drivers can
> only adapt to per-device PASID namespace. Hence, it's reasonable to
> require the singleton group.

Further, conceptually, we cannot support pasid attach/detach on multi-
device groups. If multiple devices cannot be isolated, it is difficult
to ensure that their pasid spaces are isolated from each other.
Therefore, it is wrong to attach a domain to the pasid of a device. All
devices in the group must share a domain.

Best regards,
baolu