linux-kernel - Re: [PATCH v2 3/4] iommufd: Add IOMMU_DEVICE_GET_HW

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Date:   Thu, 9 Mar 2023 13:20:58 -0400
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Baolu Lu <baolu.lu@...ux.intel.com>
Cc:     Yi Liu <yi.l.liu@...el.com>, joro@...tes.org,
        alex.williamson@...hat.com, kevin.tian@...el.com,
        robin.murphy@....com, cohuck@...hat.com, eric.auger@...hat.com,
        nicolinc@...dia.com, kvm@...r.kernel.org, mjrosato@...ux.ibm.com,
        chao.p.peng@...ux.intel.com, yi.y.sun@...ux.intel.com,
        peterx@...hat.com, jasowang@...hat.com,
        shameerali.kolothum.thodi@...wei.com, lulu@...hat.com,
        suravee.suthikulpanit@....com, iommu@...ts.linux.dev,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v2 3/4] iommufd: Add IOMMU_DEVICE_GET_HW_INFO

On Thu, Mar 09, 2023 at 09:50:18PM +0800, Baolu Lu wrote:

> > +	if (cmd->flags || cmd->__reserved || !cmd->data_len)
> > +		return -EOPNOTSUPP;
> > +
> > +	idev = iommufd_get_device(ucmd, cmd->dev_id);
> > +	if (IS_ERR(idev))
> > +		return PTR_ERR(idev);
> > +
> > +	ops = dev_iommu_ops(idev->dev);
> > +	if (!ops || !ops->hw_info) {
> 
> dev_iommu_ops() will never return a NULL.
> 
> Need below check
> 
> 	dev->iommu && dev->iommu->iommu_dev
> 
> before dev_iommu_ops(). Perhaps something like below?
> 
> 	if (!dev->iommu || !dev->iommu->iommu_dev)
> 		return -EINVAL;

At this point the device has become owned through the ownership API,
it absolutely has to have an iommu and an ops. No need to check
anything.

Jason