linux-kernel - RE: [RFC 03/20] vfio: Add vfio_[un]register

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Message-ID: <BN9PR11MB54338CA90323E2A15A8536CF8CA29@BN9PR11MB5433.namprd11.prod.outlook.com>
Date:   Wed, 22 Sep 2021 13:44:55 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     Jason Gunthorpe <jgg@...dia.com>
CC:     "Liu, Yi L" <yi.l.liu@...el.com>,
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Subject: RE: [RFC 03/20] vfio: Add vfio_[un]register_device()

> From: Jason Gunthorpe <jgg@...dia.com>
> Sent: Wednesday, September 22, 2021 8:23 PM
> 
> On Wed, Sep 22, 2021 at 09:23:34AM +0000, Tian, Kevin wrote:
> 
> > > Providing an ioctl to bind to a normal VFIO container or group might
> > > allow a reasonable fallback in userspace..
> >
> > I didn't get this point though. An error in binding already allows the
> > user to fall back to the group path. Why do we need introduce another
> > ioctl to explicitly bind to container via the nongroup interface?
> 
> New userspace still needs a fallback path if it hits the 'try and
> fail'. Keeping the device FD open and just using a different ioctl to
> bind to a container/group FD, which new userspace can then obtain as a
> fallback, might be OK.
> 
> Hard to see without going through the qemu parts, so maybe just keep
> it in mind
> 

sure. will figure it out when working on the qemu part.