linux-kernel - Re: [PATCH v6 0/9] vfio/mdev: IOMMU aware mediated device

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Date:   Fri, 15 Feb 2019 18:46:04 +0000
From:   Jean-Philippe Brucker <jean-philippe.brucker@....com>
To:     Alex Williamson <alex.williamson@...hat.com>,
        Lu Baolu <baolu.lu@...ux.intel.com>
Cc:     Joerg Roedel <joro@...tes.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Kirti Wankhede <kwankhede@...dia.com>,
        "ashok.raj@...el.com" <ashok.raj@...el.com>,
        "sanjay.k.kumar@...el.com" <sanjay.k.kumar@...el.com>,
        "jacob.jun.pan@...el.com" <jacob.jun.pan@...el.com>,
        "kevin.tian@...el.com" <kevin.tian@...el.com>,
        "yi.l.liu@...el.com" <yi.l.liu@...el.com>,
        "yi.y.sun@...el.com" <yi.y.sun@...el.com>,
        "peterx@...hat.com" <peterx@...hat.com>,
        "tiwei.bie@...el.com" <tiwei.bie@...el.com>,
        "xin.zeng@...el.com" <xin.zeng@...el.com>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 0/9] vfio/mdev: IOMMU aware mediated device

On 14/02/2019 20:14, Alex Williamson wrote:
>> This patch series extends both IOMMU and vfio components to support
>> mdev device passing through when it could be isolated and protected
>> by the IOMMU units. The first part of this series (PATCH 1/09~6/09)
>> adds the interfaces and implementation of the multiple domains per
>> device. The second part (PATCH 7/09~9/09) adds the iommu device
>> attribute to each mdev, determines isolation type according to the
>> existence of an iommu device when attaching group in vfio type1 iommu
>> module, and attaches the domain to iommu aware mediated devices.
>> 
>> References:
>> [1] https://software.intel.com/en-us/download/intel-virtualization-technology-for-directed-io-architecture-specification
>> [2] https://software.intel.com/en-us/download/intel-scalable-io-virtualization-technical-specification
>> [3] https://schd.ws/hosted_files/lc32018/00/LC3-SIOV-final.pdf
>> 
>> Best regards,
>> Lu Baolu
>> 
>> Change log:
>>   v5->v6:
> 
> This looks pretty reasonable with Jean-Philippe's nit fixups.  Where do
> we go from here?  I think we need an ack from Kirti since they have an
> interest here.  Presumably this looks ok to the ARM folks.

Looks great from my point of view. I focused on patch 1 since I'm
planning to reuse iommu_dev_features for SVA. I don't have time to test
auxd and mdev on SMMUv3 at the moment but I had a better look and, if it
helps, for patches 1 and 7-9:

Reviewed-by: Jean-Philippe Brucker <jean-philippe.brucker@....com>

That said, are you planning to add back the mdev_get_iommu_domain()
function, in a separate patch? Because I think the parent driver still
needs a way to retrieve the PASID for an mdev?

Thanks,
Jean

> Do we have
> any consumers of this code yet?  Theoretically I think a vfio-pci-like
> meta driver could be written as an mdev vendor driver with this support
> (restricted to type1 iommu use cases).  Thanks,
> 
> Alex