RE: [RFC v16 1/9] iommu: Introduce attach/detach_pasid_table API

Tian, Kevin
2021-12-09T04:00:04Z

> From: Tian, Kevin
> Sent: Thursday, December 9, 2021 10:58 AM
>
> For ARM it's SMMU's PASID table format. There is no step-2 since PASID
> is already within the address space covered by the user PASID table.
>

One correction here. 'no step-2' is definitely wrong here as it means
more than user page table in your plan (e.g. dpdk).

To simplify it what I meant is:

iommufd reports how many 'user page tables' are supported given a device.

ARM always reports only one can be supported, and it must be created in
PASID table format. tagged by RID.

Intel reports one in step1 (tagged by RID), and N in step2 (tagged by
RID+PASID). A special flag in attach call allows the user to specify the
additional PASID routing info for a 'user page table'.

Thanks
Kevin