[Intel-gfx] [PATCH v12 18/24] vfio: Add VFIO_DEVICE_BIND_IOMMUFD

[Liu, Yi L]

> From: Alex Williamson <alex.williamson at redhat.com>
> Sent: Tuesday, June 13, 2023 10:40 PM
> 
> On Tue, 13 Jun 2023 14:28:43 +0000
> "Liu, Yi L" <yi.l.liu at intel.com> wrote:
> 
> > > From: Alex Williamson <alex.williamson at redhat.com>
> > > Sent: Tuesday, June 13, 2023 10:18 PM
> >
> > > > > > diff --git a/include/linux/vfio.h b/include/linux/vfio.h
> > > > > > index 83cc5dc28b7a..e80a8ac86e46 100644
> > > > > > --- a/include/linux/vfio.h
> > > > > > +++ b/include/linux/vfio.h
> > > > > > @@ -66,6 +66,7 @@ struct vfio_device {
> > > > > >  	struct iommufd_device *iommufd_device;
> > > > > >  	bool iommufd_attached;
> > > > > >  #endif
> > > > > > +	bool cdev_opened:1;
> > > > >
> > > > > Perhaps a more strongly defined data type here as well and roll
> > > > > iommufd_attached into the same bit field scheme.
> > > >
> > > > Ok, then needs to make iommufd_attached always defined.
> > >
> > > That does not follow.  Thanks,
> >
> > Well, I meant the iommufd_attached now is defined only when
> > CONFIG_IOMMUFD is enabled. To toll it with cdev_opened, needs
> > to change this.
> 
> Understood, but I don't think it's true.  If defined we use one more
> bit of the bit field, which is a consideration when we approach filling
> it, but we're not using bit-shift operations to address these bits, so
> why does it matter if one has compiler conditional usage?  Thanks,

Aha, I see. So you are suggesting something like the below. Is it?

#if IS_ENABLED(CONFIG_IOMMUFD)
	struct iommufd_device *iommufd_device;
	u8 iommufd_attached:1;
#endif
	u8 cdev_opened:1;

Regards,
Yi Liu