Re: [PATCH v3 12/13] PCI/TSM: support TDI related operations for host TSM driver

[Jason Gunthorpe <jgg@nvidia.com>]

On Tue, May 27, 2025 at 05:18:01PM +0530, Aneesh Kumar K.V wrote:
> > yeah, I guess, there is a couple of places like this
> >
> > git grep pci_dev drivers/iommu/iommufd/
> >
> > drivers/iommu/iommufd/device.c:                 struct pci_dev *pdev = to_pci_dev(idev->dev);
> > drivers/iommu/iommufd/eventq.c:         struct pci_dev *pdev = to_pci_dev(dev);
> >
> > Although I do not see any compelling reason to have pci_dev in the TSM API, struct device should just work and not spill any PCI details to IOMMUFD but whatever... Thanks,
> 
> Getting the kvm reference is tricky here.

The KVM will come from the viommu object, passed in by userspace that
is the plan at least.. If you are not presenting a viommu to the guest
then I imagine we would still have some kind of NOP viommu object..

We need an association between the viommu and vdevice to tell the TSM
world what it is when we tell the TSM to create the vPCI function..

There is a missing ioctl in this sequence, you have to register the
vdev with the viommu to create a vPCI function, and that may trigger a
TSM call too.

The registration should link the vdev to the viommu and then you can
get the viommu's kvm for a later bind.

> +int iommufd_vdevice_tsm_bind_ioctl(struct iommufd_ucmd *ucmd)
> +{
> +	struct iommu_vdevice_id *cmd = ucmd->cmd;
> +	struct iommufd_vdevice *vdev;
> +	int rc = 0;
> +
> +	vdev = container_of(iommufd_get_object(ucmd->ictx, cmd->vdevice_id,
> +					       IOMMUFD_OBJ_VDEVICE),
> +			    struct iommufd_vdevice, obj);
> +	if (IS_ERR(vdev))
> +		return PTR_ERR(vdev);
> +
> +	rc = tsm_bind(vdev->dev, vdev->kvm, vdev->id);
> +	if (rc) {
> +		rc = -ENODEV;
> +		goto out_put_vdev;
> +	}
> +
> +	/* locking? */
> +	vdev->tsm_bound = true;
> +	refcount_inc(&vdev->obj.users);

This refcount isn't going to work, it will make an error close()
crash..

You need to auto-unbind on destruction I think.

Jason