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Date:   Wed, 9 Jun 2021 09:47:42 -0300
From:   Jason Gunthorpe <jgg@nvidia.com>
To:     Paolo Bonzini <pbonzini@redhat.com>
Cc:     "Tian, Kevin" <kevin.tian@intel.com>,
        Alex Williamson <alex.williamson@redhat.com>,
        Jean-Philippe Brucker <jean-philippe@linaro.org>,
        "Jiang, Dave" <dave.jiang@intel.com>,
        "Raj, Ashok" <ashok.raj@intel.com>,
        "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
        Jonathan Corbet <corbet@lwn.net>,
        Robin Murphy <robin.murphy@arm.com>,
        LKML <linux-kernel@vger.kernel.org>,
        "iommu@lists.linux-foundation.org" <iommu@lists.linux-foundation.org>,
        David Gibson <david@gibson.dropbear.id.au>,
        Kirti Wankhede <kwankhede@nvidia.com>,
        David Woodhouse <dwmw2@infradead.org>,
        Jason Wang <jasowang@redhat.com>
Subject: Re: [RFC] /dev/ioasid uAPI proposal
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On Wed, Jun 09, 2021 at 02:46:05PM +0200, Paolo Bonzini wrote:
> On 09/06/21 13:57, Jason Gunthorpe wrote:
> > On Wed, Jun 09, 2021 at 02:49:32AM +0000, Tian, Kevin wrote:
> > 
> > > Last unclosed open. Jason, you dislike symbol_get in this contract per
> > > earlier comment. As Alex explained, looks it's more about module
> > > dependency which is orthogonal to how this contract is designed. What
> > > is your opinion now?
> > 
> > Generally when you see symbol_get like this it suggests something is
> > wrong in the layering..
> > 
> > Why shouldn't kvm have a normal module dependency on drivers/iommu?
> 
> It allows KVM to load even if there's an "install /bin/false" for vfio
> (typically used together with the blacklist directive) in modprobe.conf.
> This rationale should apply to iommu as well.

I can vaugely understand this rational for vfio, but not at all for
the platform's iommu driver, sorry.

Jason