> From: Tian, Kevin <kevin.tian@xxxxxxxxx>
> Sent: Friday, January 20, 2023 4:03 PM
>
> > From: Liu, Yi L <yi.l.liu@xxxxxxxxx>
> > Sent: Tuesday, January 17, 2023 9:50 PM
> >
> > This adds two vfio device ioctls for userspace using iommufd on vfio
> > devices.
> >
> > VFIO_DEVICE_BIND_IOMMUFD: bind device to an iommufd, hence gain
> > DMA
> > control provided by the iommufd. VFIO no
> > iommu is indicated by passing a minus
> > fd value.
>
> Can't this be a flag bit for better readability than using a special value?
>
> > VFIO_DEVICE_ATTACH_IOMMUFD_PT: attach device to ioas, page
> tables
> > managed by iommufd. Attach can be
> > undo by passing IOMMUFD_INVALID_ID
> > to kernel.
>
> With Alex' remark we need a separate DETACH cmd now.
Yes.
> >
> > + /*
> > + * For group path, iommufd pointer is NULL when comes into this
> > + * helper. Its noiommu support is in container.c.
> > + *
> > + * For iommufd compat mode, iommufd pointer here is a valid value.
> > + * Its noiommu support is supposed to be in vfio_iommufd_bind().
> > + *
> > + * For device cdev path, iommufd pointer here is a valid value for
> > + * normal cases, but it is NULL if it's noiommu. The reason is
> > + * that userspace uses iommufd==-1 to indicate noiommu mode in
> > this
> > + * path. So caller of this helper will pass in a NULL iommufd
> > + * pointer. To differentiate it from the group path which also
> > + * passes NULL iommufd pointer in, df->noiommu is used. For cdev
> > + * noiommu, df->noiommu would be set to mark noiommu case for
> > cdev
> > + * path.
> > + *
> > + * So if df->noiommu is set then this helper just goes ahead to
> > + * open device. If not, it depends on if iommufd pointer is NULL
> > + * to handle the group path, iommufd compat mode, normal cases
> in
> > + * the cdev path.
> > + */
> > if (iommufd)
> > ret = vfio_iommufd_bind(device, iommufd, dev_id, pt_id);
> > - else
> > + else if (!df->noiommu)
> > ret = vfio_device_group_use_iommu(device);
> > if (ret)
> > goto err_module_put;
>
> Isn't 'ret' uninitialized when df->noiommu is true?
Done.
> > +static int vfio_ioctl_device_attach(struct vfio_device *device,
> > + struct vfio_device_feature __user *arg)
> > +{
> > + struct vfio_device_attach_iommufd_pt attach;
> > + int ret;
> > + bool is_attach;
> > +
> > + if (copy_from_user(&attach, (void __user *)arg, sizeof(attach)))
> > + return -EFAULT;
> > +
> > + if (attach.flags)
> > + return -EINVAL;
> > +
> > + if (!device->ops->bind_iommufd)
> > + return -ENODEV;
> > +
>
> this should fail if noiommu is true.
Yes.
Regards,
Yi Liu
