linux-kernel - RE: [RFC 15/20] vfio/pci: Add VFIO_DEVICE_[DE]ATTACH

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Message-ID: <BN9PR11MB5433D992DE87A7F8E09E24CF8CA29@BN9PR11MB5433.namprd11.prod.outlook.com>
Date:   Wed, 22 Sep 2021 14:17:56 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     Jason Gunthorpe <jgg@...dia.com>
CC:     "Liu, Yi L" <yi.l.liu@...el.com>,
        "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
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Subject: RE: [RFC 15/20] vfio/pci: Add VFIO_DEVICE_[DE]ATTACH_IOASID

> From: Jason Gunthorpe <jgg@...dia.com>
> Sent: Wednesday, September 22, 2021 8:59 PM
> 
> On Wed, Sep 22, 2021 at 03:56:18AM +0000, Tian, Kevin wrote:
> > > From: Jason Gunthorpe <jgg@...dia.com>
> > > Sent: Wednesday, September 22, 2021 2:04 AM
> > >
> > > On Sun, Sep 19, 2021 at 02:38:43PM +0800, Liu Yi L wrote:
> > > > This patch adds interface for userspace to attach device to specified
> > > > IOASID.
> > > >
> > > > Note:
> > > > One device can only be attached to one IOASID in this version. This is
> > > > on par with what vfio provides today. In the future this restriction can
> > > > be relaxed when multiple I/O address spaces are supported per device
> > >
> > > ?? In VFIO the container is the IOS and the container can be shared
> > > with multiple devices. This needs to start at about the same
> > > functionality.
> >
> > a device can be only attached to one container. One container can be
> > shared by multiple devices.
> >
> > a device can be only attached to one IOASID. One IOASID can be shared
> > by multiple devices.
> >
> > it does start at the same functionality.
> >
> > >
> > > > +	} else if (cmd == VFIO_DEVICE_ATTACH_IOASID) {
> > >
> > > This should be in the core code, right? There is nothing PCI specific
> > > here.
> > >
> >
> > but if you insist on a pci-wrapper attach function, we still need something
> > here (e.g. with .attach_ioasid() callback)?
> 
> I would like to stop adding ioctls to this switch, the core code
> should decode the ioctl and call an per-ioctl op like every other
> subsystem does..
> 
> If you do that then you could have an op
> 
>  .attach_ioasid = vfio_full_device_attach,
> 
> And that is it for driver changes.
> 
> Every driver that use type1 today should be updated to have the above
> line and will work with iommufd. mdevs will not be updated and won't
> work.
> 

will do.