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

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Date:   Fri, 10 Mar 2023 08:06:46 +0000
From:   "Liu, Yi L" <yi.l.liu@...el.com>
To:     Jason Gunthorpe <jgg@...dia.com>,
        Baolu Lu <baolu.lu@...ux.intel.com>
CC:     "joro@...tes.org" <joro@...tes.org>,
        "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        "robin.murphy@....com" <robin.murphy@....com>,
        "cohuck@...hat.com" <cohuck@...hat.com>,
        "eric.auger@...hat.com" <eric.auger@...hat.com>,
        "nicolinc@...dia.com" <nicolinc@...dia.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "mjrosato@...ux.ibm.com" <mjrosato@...ux.ibm.com>,
        "chao.p.peng@...ux.intel.com" <chao.p.peng@...ux.intel.com>,
        "yi.y.sun@...ux.intel.com" <yi.y.sun@...ux.intel.com>,
        "peterx@...hat.com" <peterx@...hat.com>,
        "jasowang@...hat.com" <jasowang@...hat.com>,
        "shameerali.kolothum.thodi@...wei.com" 
        <shameerali.kolothum.thodi@...wei.com>,
        "lulu@...hat.com" <lulu@...hat.com>,
        "suravee.suthikulpanit@....com" <suravee.suthikulpanit@....com>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>
Subject: RE: [PATCH v2 3/4] iommufd: Add IOMMU_DEVICE_GET_HW_INFO

> From: Jason Gunthorpe <jgg@...dia.com>
> Sent: Friday, March 10, 2023 1:21 AM
> 
> 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.

ok. so just needs to check hw_info callback.