linux-kernel - Re: [RFC 14/20] iommu/iommufd: Add iommufd_device_[de]attach

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Message-ID: <20210922125704.GN327412@nvidia.com>
Date:   Wed, 22 Sep 2021 09:57:04 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     "Tian, Kevin" <kevin.tian@...el.com>
Cc:     "Liu, Yi L" <yi.l.liu@...el.com>,
        "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "hch@....de" <hch@....de>,
        "jasowang@...hat.com" <jasowang@...hat.com>,
        "joro@...tes.org" <joro@...tes.org>,
        "jean-philippe@...aro.org" <jean-philippe@...aro.org>,
        "parav@...lanox.com" <parav@...lanox.com>,
        "lkml@...ux.net" <lkml@...ux.net>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "lushenming@...wei.com" <lushenming@...wei.com>,
        "eric.auger@...hat.com" <eric.auger@...hat.com>,
        "corbet@....net" <corbet@....net>,
        "Raj, Ashok" <ashok.raj@...el.com>,
        "yi.l.liu@...ux.intel.com" <yi.l.liu@...ux.intel.com>,
        "Tian, Jun J" <jun.j.tian@...el.com>, "Wu, Hao" <hao.wu@...el.com>,
        "Jiang, Dave" <dave.jiang@...el.com>,
        "jacob.jun.pan@...ux.intel.com" <jacob.jun.pan@...ux.intel.com>,
        "kwankhede@...dia.com" <kwankhede@...dia.com>,
        "robin.murphy@....com" <robin.murphy@....com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "dwmw2@...radead.org" <dwmw2@...radead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "baolu.lu@...ux.intel.com" <baolu.lu@...ux.intel.com>,
        "david@...son.dropbear.id.au" <david@...son.dropbear.id.au>,
        "nicolinc@...dia.com" <nicolinc@...dia.com>
Subject: Re: [RFC 14/20] iommu/iommufd: Add iommufd_device_[de]attach_ioasid()

On Wed, Sep 22, 2021 at 03:53:52AM +0000, Tian, Kevin wrote:

> Actually this was one open we closed in previous design proposal, but
> looks you have a different thought now.
> 
> vfio maintains one ioas per container. Devices in the container
> can be attached to different domains (e.g. due to snoop format). Every
> time when the ioas is updated, every attached domain is updated
> in accordance. 
> 
> You recommended one-ioas-one-domain model instead, i.e. any device 
> with a format incompatible with the one currently used in ioas has to 
> be attached to a new ioas, even if the two ioas's have the same mapping.
> This leads to compatibility check at attaching time.
> 
> Now you want returning back to the vfio model?

Oh, I thought we circled back again.. If we are all OK with one ioas
one domain then great.

> > If think sis taking in the iommfd_device then there isn't a logical
> > place to signal the PCIness
> 
> can you elaborate?

I mean just drop it and document it.

Jason