[Intel-gfx] [PATCH v3 05/15] kvm/vfio: Accept vfio device file from userspace

[Liu, Yi L]

> From: Jason Gunthorpe <jgg at nvidia.com>
> Sent: Wednesday, February 15, 2023 7:25 AM
> 
> On Tue, Feb 14, 2023 at 03:26:27PM -0700, Alex Williamson wrote:
> > > index 857d6ba349e1..d869913baafd 100644
> > > --- a/virt/kvm/vfio.c
> > > +++ b/virt/kvm/vfio.c
> > > @@ -286,18 +286,18 @@ static int kvm_vfio_set_file(struct kvm_device
> *dev, long attr,
> > >  	int32_t fd;
> > >
> > >  	switch (attr) {
> > > -	case KVM_DEV_VFIO_GROUP_ADD:
> > > +	case KVM_DEV_VFIO_FILE_ADD:
> > >  		if (get_user(fd, argp))
> > >  			return -EFAULT;
> > >  		return kvm_vfio_file_add(dev, fd);
> > >
> > > -	case KVM_DEV_VFIO_GROUP_DEL:
> > > +	case KVM_DEV_VFIO_FILE_DEL:
> > >  		if (get_user(fd, argp))
> > >  			return -EFAULT;
> > >  		return kvm_vfio_file_del(dev, fd);
> > >
> > >  #ifdef CONFIG_SPAPR_TCE_IOMMU
> > > -	case KVM_DEV_VFIO_GROUP_SET_SPAPR_TCE:
> > > +	case KVM_DEV_VFIO_FILE_SET_SPAPR_TCE:
> > >  		return kvm_vfio_file_set_spapr_tce(dev, arg);
> >
> > I don't see that the SPAPR code is so easily fungible to a device
> > file descriptor.  The kvm_vfio_spapr_tce data structure includes a
> > groupfd, which is required to match a groupfd on the file_list.  So
> > a SPAPR user cannot pass a cdev via FILE_ADD if they intend to use
> > this TCE code.
> 
> SPAPR cannot use cdev at all, cdev mode only works with iommufd.
> 
> So with my other remark about blocking unbound cdevs, in SPAPR mode
> you can never open a cdev and make it bound thus
> kvm_vfio_file_iommu_group() and others will return NULL always for
> cdev.
> 
> Thus AFAICT this is all fine.
> 
> Yi, you should also add some kconfig stuff to ensure that SPAPR always
> has the group interface compiled in.

Ok. I can make VFIO to select VFIO_GROUP for SPAPR.

Regards,
Yi Liu