linux-kernel - RE: [RFC v3 2/8] vfio/type1: Make per-application (VM) PASID quota tunable

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Date:   Wed, 5 Feb 2020 06:23:20 +0000
From:   "Liu, Yi L" <yi.l.liu@...el.com>
To:     Alex Williamson <alex.williamson@...hat.com>
CC:     "eric.auger@...hat.com" <eric.auger@...hat.com>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        "jacob.jun.pan@...ux.intel.com" <jacob.jun.pan@...ux.intel.com>,
        "joro@...tes.org" <joro@...tes.org>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        "Tian, Jun J" <jun.j.tian@...el.com>,
        "Sun, Yi Y" <yi.y.sun@...el.com>,
        "jean-philippe.brucker@....com" <jean-philippe.brucker@....com>,
        "peterx@...hat.com" <peterx@...hat.com>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [RFC v3 2/8] vfio/type1: Make per-application (VM) PASID quota
 tunable

> From: Alex Williamson [mailto:alex.williamson@...hat.com]
> Sent: Thursday, January 30, 2020 7:57 AM
> To: Liu, Yi L <yi.l.liu@...el.com>
> Subject: Re: [RFC v3 2/8] vfio/type1: Make per-application (VM) PASID quota tunable
> 
> On Wed, 29 Jan 2020 04:11:46 -0800
> "Liu, Yi L" <yi.l.liu@...el.com> wrote:
> 
> > From: Liu Yi L <yi.l.liu@...el.com>
> >
> > The PASID quota is per-application (VM) according to vfio's PASID
> > management rule. For better flexibility, quota shall be user tunable
> > . This patch provides a VFIO based user interface for which quota can
> > be adjusted. However, quota cannot be adjusted downward below the
> > number of outstanding PASIDs.
> >
> > This patch only makes the per-VM PASID quota tunable. While for the
> > way to tune the default PASID quota, it may require a new vfio module
> > option or other way. This may be another patchset in future.
> 
> If we give an unprivileged user the ability to increase their quota,
> why do we even have a quota at all?  I figured we were going to have a
> module option tunable so its under the control of the system admin.
> Thanks,

Right. I'll need to add an option. Will add it in next version. :-)

Regards,
Yi Liu