RE: [PATCH v5 10/19] vfio: Add infrastructure for bind_iommufd from userspace

["Liu, Yi L" <yi.l.liu@intel.com>]

> From: Jason Gunthorpe <jgg@nvidia.com>
> Sent: Tuesday, February 28, 2023 2:30 AM
>
> On Mon, Feb 27, 2023 at 03:11:26AM -0800, Yi Liu wrote:
> > For the device fd opened from cdev, userspace needs to bind it to an
> > iommufd and attach it to IOAS managed by iommufd. With such
> operations,
> > userspace can set up a secure DMA context and hence access device.
> >
> > This changes the existing vfio_iommufd_bind() to accept a pt_id pointer
> > as an optional input, and also an dev_id pointer to selectively return
> > the dev_id to prepare for adding bind_iommufd ioctl, which does the bind
> > first and then attach IOAS.
> >
> > Signed-off-by: Yi Liu <yi.l.liu@intel.com>
> > Reviewed-by: Kevin Tian <kevin.tian@intel.com>
> > ---
> >  drivers/vfio/group.c     | 17 ++++++++++++++---
> >  drivers/vfio/iommufd.c   | 21 +++++++++------------
> >  drivers/vfio/vfio.h      |  9 ++++++---
> >  drivers/vfio/vfio_main.c | 10 ++++++----
> >  4 files changed, 35 insertions(+), 22 deletions(-)
> >
> > diff --git a/drivers/vfio/group.c b/drivers/vfio/group.c
> > index d8771d585cb1..e44232551448 100644
> > --- a/drivers/vfio/group.c
> > +++ b/drivers/vfio/group.c
> > @@ -169,6 +169,7 @@ static void
> vfio_device_group_get_kvm_safe(struct vfio_device *device)
> >  static int vfio_device_group_open(struct vfio_device_file *df)
> >  {
> >  	struct vfio_device *device = df->device;
> > +	u32 ioas_id;
> >  	int ret;
> >
> >  	mutex_lock(&device->group->group_lock);
> > @@ -177,6 +178,13 @@ static int vfio_device_group_open(struct
> vfio_device_file *df)
> >  		goto out_unlock;
> >  	}
> >
> > +	if (device->group->iommufd) {
> > +		ret = iommufd_vfio_compat_ioas_id(device->group-
> >iommufd,
> > +						  &ioas_id);
> > +		if (ret)
> > +			goto out_unlock;
> > +	}
> 
> I don't really like this being moved out of iommufd.c
> 
> Pass in a NULL pt_id and the do some
> 
> > -int vfio_iommufd_bind(struct vfio_device *vdev, struct iommufd_ctx
> *ictx)
> > +int vfio_iommufd_bind(struct vfio_device *vdev, struct iommufd_ctx
> *ictx,
> > +		      u32 *dev_id, u32 *pt_id)
> >  {
> > -	u32 ioas_id;
> >  	u32 device_id;
> >  	int ret;
> >
> > @@ -29,17 +29,14 @@ int vfio_iommufd_bind(struct vfio_device *vdev,
> struct iommufd_ctx *ictx)
> >  	if (ret)
> >  		return ret;
> >
> > -	ret = iommufd_vfio_compat_ioas_id(ictx, &ioas_id);
> > -	if (ret)
> > -		goto err_unbind;
> 
>   io_iommufd_bind(struct vfio_device *vdev, struct iommufd_ctx *ictx,
> 		      u32 *dev_id, u32 *pt_id)
> {
>    u32 tmp_pt_id;
>    if (!pt_id) {
>        pt_id = &tmp_pt_id;
>        ret = iommufd_vfio_compat_ioas_id(ictx, pt_id);
>        if (ret)
> 		goto err_unbind;
> 
>    }
> 
> To handle it
> 
> And the commit message is sort of out of sync with the patch, more like:
> 
> vfio: Pass the pt_id as an argument to vfio_iommufd_bind()
> 
> To support binding the cdev the pt_id must come from userspace instead
> of being forced to the compat_ioas_id.
> 

Got it. not only pt_id, also dev_id. 😊

Regards,
Yi Liu