linux-kernel - Re: [PATCH v3 1/5] iommu: Return -EMEDIUMTYPE for incompatible domain and device/group

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Message-ID: <20220624181943.GV4147@nvidia.com>
Date:   Fri, 24 Jun 2022 15:19:43 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Yong Wu <yong.wu@...iatek.com>
Cc:     "Tian, Kevin" <kevin.tian@...el.com>,
        Nicolin Chen <nicolinc@...dia.com>,
        Baolu Lu <baolu.lu@...ux.intel.com>,
        "linux-s390@...r.kernel.org" <linux-s390@...r.kernel.org>,
        "cohuck@...hat.com" <cohuck@...hat.com>,
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        "robin.murphy@....com" <robin.murphy@....com>
Subject: Re: [PATCH v3 1/5] iommu: Return -EMEDIUMTYPE for incompatible
 domain and device/group

On Fri, Jun 24, 2022 at 06:35:49PM +0800, Yong Wu wrote:

> > > It's not used in VFIO context. "return 0" just satisfy the iommu
> > > framework to go ahead. and yes, here we only allow the shared
> > > "mapping-domain" (All the devices share a domain created
> > > internally).

What part of the iommu framework is trying to attach a domain and
wants to see success when the domain was not actually attached ?

> > What prevent this driver from being used in VFIO context?
> 
> Nothing prevent this. Just I didn't test.

This is why it is wrong to return success here.

Jason