linux-kernel - RE: [PATCH v3 2/5] iommufd: Destroy vdevice on idevice destroy

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Message-ID: <BL1PR11MB52712CE938B57E41C34580908C46A@BL1PR11MB5271.namprd11.prod.outlook.com>
Date: Mon, 30 Jun 2025 06:27:51 +0000
From: "Tian, Kevin" <kevin.tian@...el.com>
To: Xu Yilun <yilun.xu@...ux.intel.com>, "jgg@...dia.com" <jgg@...dia.com>,
	"jgg@...pe.ca" <jgg@...pe.ca>, "will@...nel.org" <will@...nel.org>,
	"aneesh.kumar@...nel.org" <aneesh.kumar@...nel.org>
CC: "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"joro@...tes.org" <joro@...tes.org>, "robin.murphy@....com"
	<robin.murphy@....com>, "shuah@...nel.org" <shuah@...nel.org>,
	"nicolinc@...dia.com" <nicolinc@...dia.com>, "aik@....com" <aik@....com>,
	"Williams, Dan J" <dan.j.williams@...el.com>, "baolu.lu@...ux.intel.com"
	<baolu.lu@...ux.intel.com>, "Xu, Yilun" <yilun.xu@...el.com>
Subject: RE: [PATCH v3 2/5] iommufd: Destroy vdevice on idevice destroy

> From: Xu Yilun <yilun.xu@...ux.intel.com>
> Sent: Friday, June 27, 2025 11:38 AM
> 
> +static void iommufd_device_remove_vdev(struct iommufd_device *idev)
> +{
> +	struct iommufd_vdevice *vdev;
> +
> +	mutex_lock(&idev->igroup->lock);
> +	/* vdev has been completely destroyed by userspace */
> +	if (!idev->vdev)
> +		goto out_unlock;
> +
> +	vdev = iommufd_get_vdevice(idev->ictx, idev->vdev->obj.id);
> +	if (IS_ERR(vdev)) {
> +		/*
> +		 * vdev is removed from xarray by userspace, but is not
> +		 * destroyed/freed. Since iommufd_vdevice_abort() is
> reentrant,
> +		 * safe to destroy vdev here.
> +		 */
> +		iommufd_vdevice_abort(&idev->vdev->obj);
> +		goto out_unlock;
> +	}

let's add a comment that vdev is still freed in iommufd_destroy()
in this situation.

> -void iommufd_vdevice_destroy(struct iommufd_object *obj)
> +void iommufd_vdevice_abort(struct iommufd_object *obj)
>  {
>  	struct iommufd_vdevice *vdev =
>  		container_of(obj, struct iommufd_vdevice, obj);
>  	struct iommufd_viommu *viommu = vdev->viommu;
> +	struct iommufd_device *idev = vdev->idev;
> +
> +	lockdep_assert_held(&idev->igroup->lock);
> +
> +	/*
> +	 * iommufd_vdevice_abort() could be reentrant, by
> +	 * iommufd_device_unbind() or by iommufd_destroy(). Cleanup only
> once.
> +	 */
> +	if (!viommu)
> +		return;

Just check idev->vdev, to be consistent with the other path.