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

Liu, Yi L
2023-02-28T06:59:00Z

> From: Liu, Yi L <yi.l.liu@intel.com>
> Sent: Tuesday, February 28, 2023 10:35 AM
>
> > 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.
> >

Seems like pt_id is no more needed in the vfio_iommufd_bind()
since it can get compat_ioas_id in the function itself. Cdev path
never passes a pt_id to vfio_iommufd_bind() as its attach is done
by separate ATTACH ioctl. Can we use the dev_id pointer to indicate
if it needs to get the compat ioas and attach it?

vfio_iommufd_bind(struct vfio_device *vdev, struct iommufd_ctx *ictx,
u32 *dev_id)
{
...
if (!dev_id) {
u32 ioas_id;

ret = iommufd_vfio_compat_ioas_id(ictx, &ioas_id);
if (ret)
goto err_unbind;

ret = vdev->ops->attach_ioas(vdev, &ioas_id);
if (ret)
goto err_unbind;
}
...
}

Regards,
Yi Liu