Re: [RFC PATCH 15/18] cgroup: Introduce ioasids controller

Jacob Pan
2021-03-03T21:17:26Z

Hi Tejun,

On Wed, 3 Mar 2021 10:44:28 -0500, Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> wrote:

> On Sat, Feb 27, 2021 at 02:01:23PM -0800, Jacob Pan wrote:
> > IOASIDs are used to associate DMA requests with virtual address spaces.
> > They are a system-wide limited resource made available to the userspace
> > applications. Let it be VMs or user-space device drivers.
> >
> > This RFC patch introduces a cgroup controller to address the following
> > problems:
> > 1. Some user applications exhaust all the available IOASIDs thus
> > depriving others of the same host.
> > 2. System admins need to provision VMs based on their needs for IOASIDs,
> > e.g. the number of VMs with assigned devices that perform DMA requests
> > with PASID.
>
> Please take a look at the proposed misc controller:
>
> http://lkml.kernel.org/r/20210302081705.1990283-2-vipinsh-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org
>
> Would that fit your bill?
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.

Thanks for the pointer.

Jacob

>
> Thanks.
>

Thanks,

Jacob