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

Jacob Pan
2022-03-16T20:58:32Z

Hi Kevin,

On Wed, 16 Mar 2022 07:41:34 +0000, "Tian, Kevin" <kevin.tian@intel.com>
wrote:

> > From: Jason Gunthorpe <jgg@nvidia.com>
> > Sent: Tuesday, March 15, 2022 10:33 PM
> >
> > 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.
>
Perhaps i mis-presented here, I am not using 2D array. It is an 1D xarray
for domain PASIDs only. Then I use the existing device list in each domain,
adding another xa to track per-device-domain PASIDs.
> besides that it also doesn't work when we support per-device PASID
> allocation in the future. In that case merging device PASIDs together is
> conceptually wrong.
>
Sorry, could you elaborate? If we do per-dev PASID allocation, we could use
the ioasid_set for each pdev, right?

> >
> > 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..
> >
>
> this tuple can well serve per-device PASID. 😊
>
I commented on the other email, but a simple list of tuples could have
duplicated devices since each dev could attach multiple PASIDs, right?
Should we still do two level then?

> Thanks
> Kevin

Thanks,

Jacob