On Wed, Oct 09, 2024 at 09:38:07AM -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. Delay the exit routine if refcount > is unbalanced. The refcount inc/dec will be added in the following patch. > > Signed-off-by: Nicolin Chen <nicolinc@xxxxxxxxxx> > --- > drivers/iommu/iommufd/selftest.c | 33 ++++++++++++++++++++++++-------- > 1 file changed, 25 insertions(+), 8 deletions(-) > > diff --git a/drivers/iommu/iommufd/selftest.c b/drivers/iommu/iommufd/selftest.c > index f4be87b49447..a89a865617db 100644 > --- a/drivers/iommu/iommufd/selftest.c > +++ b/drivers/iommu/iommufd/selftest.c > @@ -508,14 +508,17 @@ static bool mock_domain_capable(struct device *dev, enum iommu_cap cap) > > static struct iopf_queue *mock_iommu_iopf_queue; > > -static struct iommu_device mock_iommu_device = { > -}; > +static struct mock_iommu_device { > + struct iommu_device iommu_dev; > + wait_queue_head_t wait; Just use a completion instead of a wait_queue, a few more bytes but it is easier to code. This has some subtle issue where the device memory could be freed while a concurrent thread is going to trigger the wait. Jason