Re: [PATCH v3 08/11] iommufd/selftest: Add IOMMU_VIOMMU_TYPE_SELFTEST

[Jason Gunthorpe]

On Wed, Oct 09, 2024 at 09:38:08AM -0700, Nicolin Chen wrote:

> +static struct iommufd_viommu *
> +mock_viommu_alloc(struct iommu_device *iommu_dev, struct iommu_domain *domain,
> +		  struct iommufd_ctx *ictx, unsigned int viommu_type)
> +{
> +	struct mock_iommu_device *mock_iommu =
> +		container_of(iommu_dev, struct mock_iommu_device, iommu_dev);
> +	struct mock_viommu *mock_viommu;
> +
> +	if (viommu_type != IOMMU_VIOMMU_TYPE_SELFTEST)
> +		return ERR_PTR(-EOPNOTSUPP);

What about the default viommu? What happens then?

> +	mock_viommu = iommufd_viommu_alloc(ictx, mock_viommu, core,
> +					   &mock_viommu_ops);
> +	if (IS_ERR(mock_viommu))
> +		return ERR_CAST(mock_viommu);
> +
> +	if (!refcount_inc_not_zero(&mock_iommu->users)) {

It would be a bug if the iommu_dev being passed in was somehow
released while iommufd had hold of it through vfio. So just use
refcount_inc()

Jason