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 <nicol...@nvidia.com>
> ---
>  drivers/iommu/iommufd/selftest.c | 32 ++++++++++++++++++++++++--------
>  1 file changed, 24 insertions(+), 8 deletions(-)

Reviewed-by: Jason Gunthorpe <j...@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.

Jason

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