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Date:   Tue, 3 Nov 2020 11:22:23 -0400
From:   Jason Gunthorpe <jgg@nvidia.com>
To:     "joro@8bytes.org" <joro@8bytes.org>
CC:     "Tian, Kevin" <kevin.tian@intel.com>,
        Jason Wang <jasowang@redhat.com>,
        "Liu, Yi L" <yi.l.liu@intel.com>,
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Subject: Re: (proposal) RE: [PATCH v7 00/16] vfio: expose virtual Shared
 Virtual Addressing to VMs
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On Tue, Nov 03, 2020 at 03:35:32PM +0100, joro@8bytes.org wrote:
> On Tue, Nov 03, 2020 at 10:06:42AM -0400, Jason Gunthorpe wrote:
> > The point is that other places beyond VFIO need this
> 
> Which and why?
>
> > Sure, but sometimes it is necessary, and in those cases the answer
> > can't be "rewrite a SVA driver to use vfio"
> 
> This is getting to abstract. Can you come up with an example where
> handling this in VFIO or an endpoint device kernel driver does not work?

This whole thread was brought up by IDXD which has a SVA driver and
now wants to add a vfio-mdev driver too. SVA devices that want to be
plugged into VMs are going to be common - this architecture that a SVA
driver cannot cover the kvm case seems problematic.

Yes, everything can have a SVA driver and a vfio-mdev, it works just
fine, but it is not very clean or simple.

Jason