linux-kernel - Re: [PATCH v3 4/4] vfio/type1: Use iommu_aux_at(de)tach

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Message-ID: <ac4507d5-a5fc-d078-9bfc-f9e9fd1244e7@linux.intel.com>
Date:   Wed, 15 Jul 2020 09:00:00 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        Christoph Hellwig <hch@...radead.org>
Cc:     baolu.lu@...ux.intel.com,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Kevin Tian <kevin.tian@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Ashok Raj <ashok.raj@...el.com>, kvm@...r.kernel.org,
        Cornelia Huck <cohuck@...hat.com>,
        linux-kernel@...r.kernel.org, iommu@...ts.linux-foundation.org,
        Alex Williamson <alex.williamson@...hat.com>,
        Robin Murphy <robin.murphy@....com>
Subject: Re: [PATCH v3 4/4] vfio/type1: Use iommu_aux_at(de)tach_group() APIs

Hi Christoph and Jacob,

On 7/15/20 12:29 AM, Jacob Pan wrote:
> On Tue, 14 Jul 2020 09:25:14 +0100
> Christoph Hellwig<hch@...radead.org>  wrote:
> 
>> On Tue, Jul 14, 2020 at 01:57:03PM +0800, Lu Baolu wrote:
>>> Replace iommu_aux_at(de)tach_device() with
>>> iommu_aux_at(de)tach_group(). It also saves the
>>> IOMMU_DEV_FEAT_AUX-capable physcail device in the vfio_group data
>>> structure so that it could be reused in other places.
>> This removes the last user of iommu_aux_attach_device and
>> iommu_aux_detach_device, which can be removed now.
> it is still used in patch 2/4 inside iommu_aux_attach_group(), right?
> 

There is a need to use this interface. For example, an aux-domain is
attached to a subset of a physical device and used in the kernel. In
this usage scenario, there's no need to use vfio/mdev. The device driver
could just allocate an aux-domain and call iommu_aux_attach_device() to
setup the iommu.

Best regards,
baolu