Re: [PATCH v5 2/5] iommufd/device: Associate KVM file pointer with iommufd_device

[Souradeep Chakrabarti]

On Mon, May 25, 2026 at 09:18:13PM +0530, Aneesh Kumar K.V (Arm) wrote:
> From: Shameer Kolothum <shameerali.kolothum.thodi@xxxxxxxxxx>
> 
> TSM vDevice support needs access to the KVM associated with a VFIO device
> after the device has been bound to iommufd.
> 
> Extend iommufd_device_bind() to accept the device's KVM file and store it
> in the iommufd_device. The KVM file reference is owned by VFIO and is
> already held for the duration of the device open path.
> 
> Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@xxxxxxxxxx>
> Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
> [nicolinc: fix build error in iommufd_test_mock_domain()]
> Signed-off-by: Nicolin Chen <nicolinc@xxxxxxxxxx>
> [aneesh.kumar: Switch to use kvm_file]
> Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@xxxxxxxxxx>
> ---
>  drivers/iommu/iommufd/device.c          | 7 ++++++-
>  drivers/iommu/iommufd/iommufd_private.h | 2 ++
>  drivers/iommu/iommufd/selftest.c        | 2 +-
>  drivers/vfio/iommufd.c                  | 3 ++-
>  include/linux/iommufd.h                 | 4 +++-
>  5 files changed, 14 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c
> index 170a7005f0bc..718abdc0e627 100644
> --- a/drivers/iommu/iommufd/device.c
> +++ b/drivers/iommu/iommufd/device.c
> @@ -203,6 +203,7 @@ void iommufd_device_destroy(struct iommufd_object *obj)
>   * iommufd_device_bind - Bind a physical device to an iommu fd
>   * @ictx: iommufd file descriptor
>   * @dev: Pointer to a physical device struct
> + * @kvm_file: VM file if device belongs to a KVM VM
>   * @id: Output ID number to return to userspace for this device
>   *
>   * A successful bind establishes an ownership over the device and returns
> @@ -216,7 +217,9 @@ void iommufd_device_destroy(struct iommufd_object *obj)
>   * The caller must undo this with iommufd_device_unbind()
>   */
>  struct iommufd_device *iommufd_device_bind(struct iommufd_ctx *ictx,
> -					   struct device *dev, u32 *id)
> +					   struct device *dev,
> +					   struct file *kvm_file,
> +					   u32 *id)
could it be a neutrally-named VM-file handle (e.g. vm_file)?
>  {
>  	struct iommufd_device *idev;
>  	struct iommufd_group *igroup;
> @@ -266,6 +269,8 @@ struct iommufd_device *iommufd_device_bind(struct iommufd_ctx *ictx,
>  	if (!iommufd_selftest_is_mock_dev(dev))
>  		iommufd_ctx_get(ictx);
>  	idev->dev = dev;
For a non-KVM VMM a registrable "which VM-file type" hook (a 
file_is_mshv_partition() analogue) rather than an implicit "whatever 
VFIO set" contract will be helpful, so the type can be validated where 
it matters.
> +	/* reference is already taken in vfio_df_ioctl_bind_iommufd() */
> +	idev->kvm_file = kvm_file;
>  	idev->enforce_cache_coherency =
>  		device_iommu_capable(dev, IOMMU_CAP_ENFORCE_CACHE_COHERENCY);
>  	/* The calling driver is a user until iommufd_device_unbind() */
> diff --git a/drivers/iommu/iommufd/iommufd_private.h b/drivers/iommu/iommufd/iommufd_private.h
> index 6ac1965199e9..44eb026c206d 100644
> --- a/drivers/iommu/iommufd/iommufd_private.h
> +++ b/drivers/iommu/iommufd/iommufd_private.h
> @@ -488,6 +488,8 @@ struct iommufd_device {
>  	struct list_head group_item;
>  	/* always the physical device */
>  	struct device *dev;
> +	/* ..and the VM file if available */
> +	struct file *kvm_file;
>  	bool enforce_cache_coherency;
>  	struct iommufd_vdevice *vdev;
>  	bool destroying;
> diff --git a/drivers/iommu/iommufd/selftest.c b/drivers/iommu/iommufd/selftest.c
> index af07c642a526..a193390f9d07 100644
> --- a/drivers/iommu/iommufd/selftest.c
> +++ b/drivers/iommu/iommufd/selftest.c
> @@ -1069,7 +1069,7 @@ static int iommufd_test_mock_domain(struct iommufd_ucmd *ucmd,
>  		goto out_sobj;
>  	}
>  
> -	idev = iommufd_device_bind(ucmd->ictx, &sobj->idev.mock_dev->dev,
> +	idev = iommufd_device_bind(ucmd->ictx, &sobj->idev.mock_dev->dev, NULL,
>  				   &idev_id);
>  	if (IS_ERR(idev)) {
>  		rc = PTR_ERR(idev);
> diff --git a/drivers/vfio/iommufd.c b/drivers/vfio/iommufd.c
> index a38d262c6028..d2d0bd9382a1 100644
> --- a/drivers/vfio/iommufd.c
> +++ b/drivers/vfio/iommufd.c
> @@ -119,7 +119,8 @@ int vfio_iommufd_physical_bind(struct vfio_device *vdev,
>  {
>  	struct iommufd_device *idev;
>  
> -	idev = iommufd_device_bind(ictx, vdev->dev, out_device_id);
> +	idev = iommufd_device_bind(ictx, vdev->dev, vdev->kvm_file,
> +				   out_device_id);
>  	if (IS_ERR(idev))
>  		return PTR_ERR(idev);
>  	vdev->iommufd_device = idev;
> diff --git a/include/linux/iommufd.h b/include/linux/iommufd.h
> index 6e7efe83bc5d..0a0bb4abfbd2 100644
> --- a/include/linux/iommufd.h
> +++ b/include/linux/iommufd.h
> @@ -59,7 +59,9 @@ struct iommufd_object {
>  };
>  
>  struct iommufd_device *iommufd_device_bind(struct iommufd_ctx *ictx,
> -					   struct device *dev, u32 *id);
> +					   struct device *dev,
> +					   struct file *kvm_file,
> +					   u32 *id);
>  void iommufd_device_unbind(struct iommufd_device *idev);
>  
>  int iommufd_device_attach(struct iommufd_device *idev, ioasid_t pasid,
> -- 
> 2.43.0
>