From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jason Gunthorpe <jgg-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
Subject: Re: [RFC PATCH 15/18] cgroup: Introduce ioasids controller
Date: Wed, 3 Mar 2021 20:23:57 -0400
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To: Jacob Pan <jacob.jun.pan-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
Cc: "Tian, Kevin" <kevin.tian-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>, Alex Williamson <alex.williamson-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Raj Ashok <ashok.raj-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>, Jonathan Corbet <corbet-T1hC0tSOHrs@public.gmane.org>, Jean-Philippe Brucker <jean-philippe-68IGFXMjmZ7QT0dZR+AlfA@public.gmane.org>, LKML <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Dave Jiang <dave.jiang-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>, iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>, Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Wu Hao <hao.wu-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>, David Woodhouse <dwmw2-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>

On Wed, Mar 03, 2021 at 04:02:05PM -0800, Jacob Pan wrote:
> > The interface definitely can be reused. But IOASID has a different
> > behavior in terms of migration and ownership checking. I guess SEV key
> > IDs are not tied to a process whereas IOASIDs are. Perhaps this can be
> > solved by adding
> > +	.can_attach	= ioasids_can_attach,
> > +	.cancel_attach	= ioasids_cancel_attach,
> > Let me give it a try and come back.
> > 
> While I am trying to fit the IOASIDs cgroup in to the misc cgroup proposal.
> I'd like to have a direction check on whether this idea of using cgroup for
> IOASID/PASID resource management is viable.
> 
> Alex/Jason/Jean and everyone, your feedback is much appreciated.

IMHO I can't think of anything else to enforce some limit on a HW
scarce resource that unpriv userspace can consume.

Jason