Re: [PATCH v12 07/17] iommu: Try to allocate blocking domain when probing device

[Jason Gunthorpe]

On Fri, Aug 26, 2022 at 08:11:31PM +0800, Lu Baolu wrote:
> Allocate the blocking domain when probing devices if the driver supports
> blocking domain allocation. Otherwise, revert to the previous behavior,
> that is, use UNMANAGED domain instead when the blocking domain is needed.
> 
> Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> Tested-by: Zhangfei Gao <zhangfei.gao@xxxxxxxxxx>
> Tested-by: Tony Zhu <tony.zhu@xxxxxxxxx>
> ---
>  drivers/iommu/iommu.c | 29 +++++++++++++++++------------
>  1 file changed, 17 insertions(+), 12 deletions(-)

This seems like a lot of overhead to allocate these things for every
group?

Why not add a simple refcount on the blocking domain instead and
allocate the domain on the pasid attach like we do for ownership?

Jason