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

[Jason Gunthorpe]

On Mon, Aug 29, 2022 at 11:40:24AM +0800, Baolu Lu wrote:
> On 2022/8/26 22:52, Jason Gunthorpe wrote:
> > 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?
> 
> I am working towards implementing static instance of blocking domain for
> each IOMMU driver, and then, there's no much overhead to allocate it in
> the probing device path.

Well, I thought about that and I don't think we can get
there in a short order. Would rather you progress this series without
getting entangled in such a big adventure

Jason