linux-kernel - RE: [RFC PATCH v2 00/10] vfio/mdev: IOMMU aware mediated device

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Date:   Wed, 5 Sep 2018 03:01:39 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     Lu Baolu <baolu.lu@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>,
        "David Woodhouse" <dwmw2@...radead.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Kirti Wankhede <kwankhede@...dia.com>
CC:     "Raj, Ashok" <ashok.raj@...el.com>,
        "Kumar, Sanjay K" <sanjay.k.kumar@...el.com>,
        "Pan, Jacob jun" <jacob.jun.pan@...el.com>,
        Jean-Philippe Brucker <jean-philippe.brucker@....com>,
        "Liu, Yi L" <yi.l.liu@...el.com>, "Sun, Yi Y" <yi.y.sun@...el.com>,
        "peterx@...hat.com" <peterx@...hat.com>,
        "Bie, Tiwei" <tiwei.bie@...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: [RFC PATCH v2 00/10] vfio/mdev: IOMMU aware mediated device

> From: Lu Baolu [mailto:baolu.lu@...ux.intel.com]
> Sent: Thursday, August 30, 2018 12:09 PM
> 
[...]
> 
> In order to distinguish the IOMMU-capable mediated devices from those
> which still need to rely on parent devices, this patch set adds a
> domain type attribute to each mdev.
> 
> enum mdev_domain_type {
> 	DOMAIN_TYPE_NO_IOMMU,	/* Don't need any IOMMU support.
> 				 * All isolation and protection
> 				 * are handled by the parent
> 				 * device driver with a device
> 				 * specific mechanism.
> 				 */
> 	DOMAIN_TYPE_ATTACH_PARENT, /* IOMMU can isolate and
> protect
> 				    * the mdev, and the isolation
> 				    * domain should be attaced with
> 				    * the parent device.
> 				    */
> };
> 

ATTACH_PARENT is not like a good counterpart to NO_IOMMU.

what about DOMAIN_TYPE_NO_IOMMU/DOMAIN_TYPE_IOMMU? whether
to attach parent device is just internal logic.

Alternatively DOMAIN_TYPE_SOFTWARE/DOMAIN_TYPE_HARDWARE,
where software means iommu_domain is managed by software while
the other means managed by hardware.

One side note to Alex - with multiple domain extension in IOMMU layer,
this version combines IOMMU-capable usages in VFIO: PASID-based (as 
in scalable iov) and RID-based (as the usage of mdev wrapper on any 
device). Both cases share the common path - just binding the domain to the
parent device of mdev. IOMMU layer will handle two cases differently later. 

Thanks
Kevin