RE: [PATCH v2 1/3] iommufd: Add devices_users to track the hw_pagetable usage by device

Liu, Yi L
2023-01-30T02:22:30Z

> From: Tian, Kevin <kevin.tian@intel.com>
> Sent: Sunday, January 29, 2023 5:23 PM
>
> > hw_pagetable by the attached devices. Make this field as a pointer, only
> > allocate for a stage-2 hw_pagetable. A stage-1 hw_pagetable should
> reuse
> > the stage-2 hw_pagetable's devices_users, because when a device
> attaches
> > to a stage-1 hw_pagetable, linking the stage-2 hwpt to the IOAS is still
> > required. So, with a nested configuration, increase the devices_users on
> > the stage-2 (parent) hwpt, no matter a device is attached to the stage-1
> > or the stage-2 hwpt.
>
> Above is very confusing w/o seeing the full series of nesting support.
>
> As a preparatory step this should focus on existing code and what this
> series tries to achieve. e.g. I'd not make device_users a pointer here.
> Do that incrementally when the nesting support comes.

Yes, in the below branch, I've moved this patch to be together with the nesting
commits. Maybe I can send out the nesting RFC.

https://github.com/yiliu1765/iommufd/commits/wip/iommufd-v6.2-rc4-nesting

Regards,
Yi Liu