Re: [PATCH v2 3/8] iommu/vt-d: Implement device_pasid domain attach ops

[Jason Gunthorpe]

On Tue, Mar 15, 2022 at 03:36:20PM -0700, Jacob Pan wrote:
> Hi Jason,
> 
> On Tue, 15 Mar 2022 11:33:22 -0300, Jason Gunthorpe <jgg@xxxxxxxxxx> wrote:
> 
> > On Mon, Mar 14, 2022 at 10:07:07PM -0700, Jacob Pan wrote:
> > > +	/*
> > > +	 * Each domain could have multiple devices attached with
> > > shared or per
> > > +	 * device PASIDs. At the domain level, we keep track of unique
> > > PASIDs and
> > > +	 * device user count.
> > > +	 * E.g. If a domain has two devices attached, device A has
> > > PASID 0, 1;
> > > +	 * device B has PASID 0, 2. Then the domain would have PASID
> > > 0, 1, 2.
> > > +	 */  
> > 
> > A 2d array of xarray's seems like a poor data structure for this task.
> > 
> > AFACIT this wants to store a list of (device, pasid) tuples, so a
> > simple linked list, 1d xarray vector or a red black tree seems more
> > appropriate..
> > 
> Agreed.
> It might need some surgery for dmar_domain and device_domain_info, which
> already has a simple device list. I am trying to leverage the existing data
> struct, let me take a closer look.

Maybe the core code should provide this data structure in the
iommu_domain.

Figuring out what stuff is attached is something every driver has to
do right?

Jason