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

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Date:   Wed, 3 Mar 2021 13:17:26 -0800
From:   Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:     Tejun Heo <tj@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Joerg Roedel <joro@...tes.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        David Woodhouse <dwmw2@...radead.org>,
        iommu@...ts.linux-foundation.org, cgroups@...r.kernel.org,
        Li Zefan <lizefan@...wei.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Eric Auger <eric.auger@...hat.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Jonathan Corbet <corbet@....net>,
        Raj Ashok <ashok.raj@...el.com>,
        "Tian, Kevin" <kevin.tian@...el.com>, Yi Liu <yi.l.liu@...el.com>,
        Wu Hao <hao.wu@...el.com>, Dave Jiang <dave.jiang@...el.com>,
        jacob.jun.pan@...ux.intel.com
Subject: Re: [RFC PATCH 15/18] cgroup: Introduce ioasids controller

Hi Tejun,

On Wed, 3 Mar 2021 10:44:28 -0500, Tejun Heo <tj@...nel.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@google.com
> 
> 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