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Subject: Re: [RFC PATCH v2 08/10] vfio/type1: Add domain at(de)taching group
 helpers
To:     Lu Baolu <baolu.lu@linux.intel.com>,
        Joerg Roedel <joro@8bytes.org>,
        David Woodhouse <dwmw2@infradead.org>,
        Alex Williamson <alex.williamson@redhat.com>,
        Kirti Wankhede <kwankhede@nvidia.com>
Cc:     kevin.tian@intel.com, ashok.raj@intel.com, tiwei.bie@intel.com,
        sanjay.k.kumar@intel.com, iommu@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org, yi.y.sun@intel.com,
        jacob.jun.pan@intel.com, kvm@vger.kernel.org
References: <20180830040922.30426-1-baolu.lu@linux.intel.com>
 <20180830040922.30426-9-baolu.lu@linux.intel.com>
From:   Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
Message-ID: <c5124ac1-65fe-7f89-265c-bef229bc5ce9@arm.com>
Date:   Mon, 10 Sep 2018 17:23:13 +0100
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On 30/08/2018 05:09, Lu Baolu wrote:
> +static int vfio_detach_aux_domain(struct device *dev, void *data)
> +{
> +	struct iommu_domain *domain = data;
> +
> +	vfio_mdev_set_aux_domain(dev, NULL);
> +	iommu_detach_device(domain, dev->parent);

I think that's only going to work for vt-d, which doesn't use a
default_domain. For other drivers, iommu.c ends up calling
domain->ops->attach_dev(default_domain, dev) here, which isn't what we want.

That was my concern with reusing attach/detach_dev callbacks for PASID
management. The attach_dev code of IOMMU drivers already has to deal
with toggling between default and unmanaged domain. Dealing with more
state transitions in the same path is going to be difficult.

Thanks,
Jean