Re: [RFC v2 1/4] hisi-acc-vfio-pci: add new vfio_pci driver for HiSilicon ACC devices

[Max Gurtovoy]

On 7/5/2021 11:47 AM, Shameerali Kolothum Thodi wrote:
> > -----Original Message-----
> > From: Leon Romanovsky [mailto:leon@xxxxxxxxxx]
> > Sent: 04 July 2021 08:04
> > To: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@xxxxxxxxxx>
> > Cc: kvm@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> > linux-crypto@xxxxxxxxxxxxxxx; alex.williamson@xxxxxxxxxx; jgg@xxxxxxxxxx;
> > mgurtovoy@xxxxxxxxxx; Linuxarm <linuxarm@xxxxxxxxxx>; liulongfang
> > <liulongfang@xxxxxxxxxx>; Zengtao (B) <prime.zeng@xxxxxxxxxxxxx>;
> > yuzenghui <yuzenghui@xxxxxxxxxx>; Jonathan Cameron
> > <jonathan.cameron@xxxxxxxxxx>; Wangzhou (B) <wangzhou1@xxxxxxxxxxxxx>
> > Subject: Re: [RFC v2 1/4] hisi-acc-vfio-pci: add new vfio_pci driver for HiSilicon
> > ACC devices
> >
> > On Fri, Jul 02, 2021 at 10:58:46AM +0100, Shameer Kolothum wrote:
> > > Add a vendor-specific vfio_pci driver for HiSilicon ACC devices.
> > > This will be extended in follow-up patches to add support for
> > > vfio live migration feature.
> > >
> > > Signed-off-by: Shameer Kolothum
> > <shameerali.kolothum.thodi@xxxxxxxxxx>
> > > ---
> > >   drivers/vfio/pci/Kconfig             |   9 +++
> > >   drivers/vfio/pci/Makefile            |   2 +
> > >   drivers/vfio/pci/hisi_acc_vfio_pci.c | 100 +++++++++++++++++++++++++++
> > >   3 files changed, 111 insertions(+)
> > >   create mode 100644 drivers/vfio/pci/hisi_acc_vfio_pci.c
> > <...>
> >
> > > +static const struct vfio_device_ops hisi_acc_vfio_pci_ops = {
> > > +	.name		= "hisi-acc-vfio-pci",
> > > +	.open		= hisi_acc_vfio_pci_open,
> > > +	.release	= vfio_pci_core_release,
> > > +	.ioctl		= vfio_pci_core_ioctl,
> > > +	.read		= vfio_pci_core_read,
> > > +	.write		= vfio_pci_core_write,
> > > +	.mmap		= vfio_pci_core_mmap,
> > > +	.request	= vfio_pci_core_request,
> > > +	.match		= vfio_pci_core_match,
> > > +	.reflck_attach	= vfio_pci_core_reflck_attach,
> > I don't remember what was proposed in vfio-pci-core conversion patches,
> > but would expect that default behaviour is to fallback to vfio_pci_core_* API
> > if ".release/.ioctl/e.t.c" are not redefined.
> Yes, that would be nice, but don't think it does that in latest(v4).
>
> Hi Max,
> Could we please consider fall back to the core defaults, may be check and assign defaults
> in vfio_pci_core_register_device() ?

I don't see why we should do this.

vfio_pci_core.ko is just a library driver. It shouldn't decide for the 
vendor driver ops.

If a vendor driver would like to use its helper functions - great.

If it wants to override it - great.

If it wants to leave some op as NULL - it can do it also.


> Thanks,
> Shameer