[PATCH v5 09/13] iommufd/selftest: Add refcount to mock_iommu_device

[Nicolin Chen]

On Tue, Oct 29, 2024 at 12:34:38PM -0300, Jason Gunthorpe wrote:
> On Fri, Oct 25, 2024 at 04:49:49PM -0700, Nicolin Chen wrote:
> > For an iommu_dev that can unplug (so far only this selftest does so), the
> > viommu->iommu_dev pointer has no guarantee of its life cycle after it is
> > copied from the idev->dev->iommu->iommu_dev.
> > 
> > Track the user count of the iommu_dev. Postpone the exit routine using a
> > completion, if refcount is unbalanced. The refcount inc/dec will be added
> > in the following patch.
> > 
> > Signed-off-by: Nicolin Chen <nicolinc at nvidia.com>
> > ---
> >  drivers/iommu/iommufd/selftest.c | 32 ++++++++++++++++++++++++--------
> >  1 file changed, 24 insertions(+), 8 deletions(-)
> 
> Reviewed-by: Jason Gunthorpe <jgg at nvidia.com>
> 
> Since this is built into the iommufd module it can't be unloaded
> without also unloading iommufd, which is impossible as long as any
> iommufd FDs are open. So I expect that the WARN_ON can never happen.

Hmm, I assume we still need this patch then?

Could a faulty "--force" possibly trigger it?

Nicolin