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To:     Jason Gunthorpe <jgg@nvidia.com>
Cc:     "Tian, Kevin" <kevin.tian@intel.com>,
        Alex Williamson <alex.williamson@redhat.com>,
        Jean-Philippe Brucker <jean-philippe@linaro.org>,
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        Jonathan Corbet <corbet@lwn.net>,
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        "iommu@lists.linux-foundation.org" <iommu@lists.linux-foundation.org>,
        David Gibson <david@gibson.dropbear.id.au>,
        Kirti Wankhede <kwankhede@nvidia.com>,
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        Jason Wang <jasowang@redhat.com>
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From:   Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: [RFC] /dev/ioasid uAPI proposal
Message-ID: <8433033c-daf2-c9b7-56f7-e354320dc5b5@redhat.com>
Date:   Wed, 9 Jun 2021 15:24:11 +0200
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On 09/06/21 14:47, Jason Gunthorpe wrote:
> 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.

Sorry, should apply to ioasid, not iommu (assuming that /dev/ioasid 
support would be modular).

Paolo