linux-kernel - RE: [PATCH v1 7/8] iommufd/device: Use iommu_group_replace

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Message-ID: <BN9PR11MB5276E4D38184A2910A7661B38CDB9@BN9PR11MB5276.namprd11.prod.outlook.com>
Date:   Tue, 7 Feb 2023 00:37:01 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     Nicolin Chen <nicolinc@...dia.com>
CC:     "jgg@...dia.com" <jgg@...dia.com>,
        "joro@...tes.org" <joro@...tes.org>,
        "will@...nel.org" <will@...nel.org>,
        "robin.murphy@....com" <robin.murphy@....com>,
        "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "shuah@...nel.org" <shuah@...nel.org>,
        "Liu, Yi L" <yi.l.liu@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>,
        "baolu.lu@...ux.intel.com" <baolu.lu@...ux.intel.com>
Subject: RE: [PATCH v1 7/8] iommufd/device: Use iommu_group_replace_domain()

> From: Nicolin Chen <nicolinc@...dia.com>
> Sent: Tuesday, February 7, 2023 3:18 AM
> 
> On Mon, Feb 06, 2023 at 08:46:04AM +0000, Tian, Kevin wrote:
> > > From: Nicolin Chen <nicolinc@...dia.com>
> > > Sent: Thursday, February 2, 2023 3:05 PM
> > >
> > > @@ -246,6 +249,18 @@ static int iommufd_device_do_attach(struct
> > > iommufd_device *idev,
> > >               }
> > >       }
> > >
> > > +     if (cur_hwpt) {
> > > +             /* Replace the cur_hwpt */
> > > +             mutex_lock(&cur_hwpt->devices_lock);
> > > +             if (cur_hwpt->ioas != hwpt->ioas)
> > > +                     iopt_remove_reserved_iova(&cur_hwpt->ioas->iopt,
> > > +                                               idev->dev);
> > > +             list_del(&cur_hwpt->hwpt_item);
> >
> > emmm shouldn't this be done only when the device is the last
> > one attached to the hwpt? and if it's the last one you should
> > also iopt_table_remove_domain() together with list_del, i.e.
> > similar housekeeping as done in iommufd_device_detach().
> 
> You are right. I had another patch on top of this series,
> moving this list_del() and iopt_table_remove_domain() to
> the destroy() callback, so I overlooked.
> 
> And I just found that the list_add_del(hwpt_item) in the
> IOMMUFD_OBJ_HW_PAGETABLE case doesn't seem to call at the
> first device's attachment. So, I think that we might need
> my previous "symmetric" patch in this series too.
> 

Yes, that makes sense.