linux-kernel - Re: [PATCH v3 03/16] iommufd/viommu: Add IOMMU_VDEVICE

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Message-ID: <20241021122248.GQ3559746@nvidia.com>
Date: Mon, 21 Oct 2024 09:22:48 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: Nicolin Chen <nicolinc@...dia.com>
Cc: kevin.tian@...el.com, will@...nel.org, joro@...tes.org,
	suravee.suthikulpanit@....com, robin.murphy@....com,
	dwmw2@...radead.org, baolu.lu@...ux.intel.com, shuah@...nel.org,
	linux-kernel@...r.kernel.org, iommu@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org,
	linux-kselftest@...r.kernel.org, eric.auger@...hat.com,
	jean-philippe@...aro.org, mdf@...nel.org, mshavit@...gle.com,
	shameerali.kolothum.thodi@...wei.com, smostafa@...gle.com,
	yi.l.liu@...el.com, aik@....com, patches@...ts.linux.dev
Subject: Re: [PATCH v3 03/16] iommufd/viommu: Add IOMMU_VDEVICE_ALLOC ioctl

On Sat, Oct 19, 2024 at 06:42:30PM -0700, Nicolin Chen wrote:
> > But be mindful of this abort, it doesn't want to be inside the lock if
> > it also gets the lock.. fail_nth should be updated to cover these new
> > ioctls to look for tricky things like that
> 
> I added an abort() beside destroy():
> 
> +void iommufd_vdevice_abort(struct iommufd_object *obj)
> +{
> +       struct iommufd_vdevice *old, *vdev =
> +               container_of(obj, struct iommufd_vdevice, obj);
> +       struct iommufd_viommu *viommu = vdev->viommu;
> +       struct iommufd_device *idev = vdev->idev;
> +
> +       lockdep_assert_not_held(&idev->igroup->lock);

???

> +
> +       if (viommu->ops && viommu->ops->vdevice_free)
> +               viommu->ops->vdevice_free(vdev);
> +
> +       old = xa_cmpxchg(&viommu->vdevs, vdev->id, vdev, NULL, GFP_KERNEL);
> +       if (old)
> +               WARN_ON(old != vdev);
> +
> +       refcount_dec(&viommu->obj.users);
> +       refcount_dec(&idev->obj.users);
> +       idev->vdev = NULL;
> +}
> +
> +void iommufd_vdevice_destroy(struct iommufd_object *obj)
> +{
> +       struct iommufd_vdevice *vdev =
> +               container_of(obj, struct iommufd_vdevice, obj);
> +
> +       mutex_lock(&vdev->idev->igroup->lock);
> +       iommufd_vdevice_abort(obj);

When we get it here??

Jason