linux-kernel - RE: [PATCH v6 1/5] iommu: Return -EMEDIUMTYPE for incompatible domain and device/group

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Message-ID: <BN9PR11MB52761E126D797ED865DC3E8B8C479@BN9PR11MB5276.namprd11.prod.outlook.com>
Date:   Tue, 13 Sep 2022 02:24:27 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     Nicolin Chen <nicolinc@...dia.com>,
        Robin Murphy <robin.murphy@....com>,
        Joerg Roedel <joro@...tes.org>,
        Jason Gunthorpe <jgg@...dia.com>
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Subject: RE: [PATCH v6 1/5] iommu: Return -EMEDIUMTYPE for incompatible domain
 and device/group

> From: Nicolin Chen <nicolinc@...dia.com>
> Sent: Sunday, September 11, 2022 7:36 AM
> 
> On Thu, Sep 08, 2022 at 09:08:38AM -0300, Jason Gunthorpe wrote:
> > On Thu, Sep 08, 2022 at 09:30:57AM +0000, Tian, Kevin wrote:
> 
> > > There are also cases where common kAPIs are called in the attach
> > > path which may return -EINVAL and random errno, e.g.:
> > >
> > > omap_iommu_attach_dev()
> > >   omap_iommu_attach()
> > >     iommu_enable()
> > >       pm_runtime_get_sync()
> > >         __pm_runtime_resume()
> > >           rpm_resume()
> > > 	if (dev->power.runtime_error) {
> > > 		retval = -EINVAL;
> 
> > Yes, this is was also on my mind with choosing an unpopular return
> > code, it has a higher chance of not coming out of some other kernel
> > API
> 
> I wonder if it would be safe to just treat a pm_runtime_get_sync()
> failure as -ENODEV, since a PM resume() mostly occurs to the IOMMU
> that an IOMMU client/master device is behind, while an iommu_domain
> rarely intervenes.

Yes, this is a condition preventing the device from being attached by
a domain hence converting -EINVAL to -ENODEV probably makes sense.
But as replied in another we might want to keep other errno's as is.