From: Lu Baolu <baolu.lu@linux.intel.com>
To: Jason Gunthorpe <jgg@nvidia.com>, Joerg Roedel <joro@8bytes.org>
Cc: baolu.lu@linux.intel.com, "Tian, Kevin" <kevin.tian@intel.com>,
"Alex Williamson (alex.williamson@redhat.com)"
<alex.williamson@redhat.com>,
Jean-Philippe Brucker <jean-philippe@linaro.org>,
David Gibson <david@gibson.dropbear.id.au>,
Jason Wang <jasowang@redhat.com>,
"parav@mellanox.com" <parav@mellanox.com>,
"Enrico Weigelt, metux IT consult" <lkml@metux.net>,
Paolo Bonzini <pbonzini@redhat.com>,
Shenming Lu <lushenming@huawei.com>,
Eric Auger <eric.auger@redhat.com>,
Jonathan Corbet <corbet@lwn.net>,
"Raj, Ashok" <ashok.raj@intel.com>,
"Liu, Yi L" <yi.l.liu@intel.com>, "Wu, Hao" <hao.wu@intel.com>,
"Jiang, Dave" <dave.jiang@intel.com>,
Jacob Pan <jacob.jun.pan@linux.intel.com>,
Kirti Wankhede <kwankhede@nvidia.com>,
Robin Murphy <robin.murphy@arm.com>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"iommu@lists.linux-foundation.org"
<iommu@lists.linux-foundation.org>,
David Woodhouse <dwmw2@infradead.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: Plan for /dev/ioasid RFC v2
Date: Thu, 10 Jun 2021 13:50:22 +0800 [thread overview]
Message-ID: <14d884a8-13bc-b2ba-7020-94b219e3e2d9@linux.intel.com> (raw)
In-Reply-To: <20210609123919.GA1002214@nvidia.com>
On 6/9/21 8:39 PM, Jason Gunthorpe wrote:
> On Wed, Jun 09, 2021 at 02:24:03PM +0200, Joerg Roedel wrote:
>> On Mon, Jun 07, 2021 at 02:58:18AM +0000, Tian, Kevin wrote:
>>> - Device-centric (Jason) vs. group-centric (David) uAPI. David is not fully
>>> convinced yet. Based on discussion v2 will continue to have ioasid uAPI
>>> being device-centric (but it's fine for vfio to be group-centric). A new
>>> section will be added to elaborate this part;
>> I would vote for group-centric here. Or do the reasons for which VFIO is
>> group-centric not apply to IOASID? If so, why?
> VFIO being group centric has made it very ugly/difficult to inject
> device driver specific knowledge into the scheme.
>
> The device driver is the only thing that knows to ask:
> - I need a SW table for this ioasid because I am like a mdev
> - I will issue TLPs with PASID
> - I need a IOASID linked to a PASID
> - I am a devices that uses ENQCMD and vPASID
> - etc in future
>
> The current approach has the group try to guess the device driver
> intention in the vfio type 1 code.
>
> I want to see this be clean and have the device driver directly tell
> the iommu layer what kind of DMA it plans to do, and thus how it needs
> the IOMMU and IOASID configured.
>
> This is the source of the ugly symbol_get and the very, very hacky 'if
> you are a mdev*and* a iommu then you must want a single PASID' stuff
> in type1.
>
> The group is causing all this mess because the group knows nothing
> about what the device drivers contained in the group actually want.
>
> Further being group centric eliminates the possibility of working in
> cases like !ACS. How do I use PASID functionality of a device behind a
> !ACS switch if the uAPI forces all IOASID's to be linked to a group,
> not a device?
>
> Device centric with an report that "all devices in the group must use
> the same IOASID" covers all the new functionality, keep the old, and
> has a better chance to keep going as a uAPI into the future.
The iommu_group can guarantee the isolation among different physical
devices (represented by RIDs). But when it comes to sub-devices (ex.
mdev or vDPA devices represented by RID + SSID), we have to rely on the
device driver for isolation. The devices which are able to generate sub-
devices should either use their own on-device mechanisms or use the
platform features like Intel Scalable IOV to isolate the sub-devices.
Under above conditions, different sub-device from a same RID device
could be able to use different IOASID. This seems to means that we can't
support mixed mode where, for example, two RIDs share an iommu_group and
one (or both) of them have sub-devices.
AIUI, when we attach a "RID + SSID" to an IOASID, we should require that
the RID doesn't share the iommu_group with any other RID.
Best regards,
baolu
next prev parent reply other threads:[~2021-06-10 5:51 UTC|newest]
Thread overview: 81+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-07 2:58 Plan for /dev/ioasid RFC v2 Tian, Kevin
2021-06-09 8:14 ` Eric Auger
2021-06-09 9:37 ` Tian, Kevin
2021-06-09 10:14 ` Eric Auger
2021-06-09 9:01 ` Leon Romanovsky
2021-06-09 9:43 ` Tian, Kevin
2021-06-09 12:24 ` Joerg Roedel
2021-06-09 12:39 ` Jason Gunthorpe
2021-06-09 13:32 ` Joerg Roedel
2021-06-09 15:00 ` Jason Gunthorpe
2021-06-09 15:51 ` Joerg Roedel
2021-06-09 16:15 ` Alex Williamson
2021-06-09 16:27 ` Alex Williamson
2021-06-09 18:49 ` Jason Gunthorpe
2021-06-10 15:38 ` Alex Williamson
2021-06-11 0:58 ` Tian, Kevin
2021-06-11 21:38 ` Alex Williamson
2021-06-14 3:09 ` Tian, Kevin
2021-06-14 3:22 ` Alex Williamson
2021-06-15 1:05 ` Tian, Kevin
2021-06-14 13:38 ` Jason Gunthorpe
2021-06-15 1:21 ` Tian, Kevin
2021-06-15 16:56 ` Alex Williamson
2021-06-16 6:53 ` Tian, Kevin
2021-06-24 4:50 ` David Gibson
2021-06-11 16:45 ` Jason Gunthorpe
2021-06-11 19:38 ` Alex Williamson
2021-06-12 1:28 ` Jason Gunthorpe
2021-06-12 16:57 ` Alex Williamson
2021-06-14 14:07 ` Jason Gunthorpe
2021-06-14 16:28 ` Alex Williamson
2021-06-14 19:40 ` Jason Gunthorpe
2021-06-15 2:31 ` Tian, Kevin
2021-06-15 16:12 ` Alex Williamson
2021-06-16 6:43 ` Tian, Kevin
2021-06-16 19:39 ` Alex Williamson
2021-06-17 3:39 ` Liu Yi L
2021-06-17 7:31 ` Tian, Kevin
2021-06-17 21:14 ` Alex Williamson
2021-06-18 0:19 ` Jason Gunthorpe
2021-06-18 16:57 ` Tian, Kevin
2021-06-18 18:23 ` Jason Gunthorpe
2021-06-25 10:27 ` Tian, Kevin
2021-06-25 14:36 ` Jason Gunthorpe
2021-06-28 1:09 ` Tian, Kevin
2021-06-28 22:31 ` Alex Williamson
2021-06-28 22:48 ` Jason Gunthorpe
2021-06-28 23:09 ` Alex Williamson
2021-06-28 23:13 ` Jason Gunthorpe
2021-06-29 0:26 ` Tian, Kevin
2021-06-29 0:28 ` Tian, Kevin
2021-06-29 0:43 ` Tian, Kevin
2021-06-28 2:03 ` Tian, Kevin
2021-06-28 14:41 ` Jason Gunthorpe
2021-06-28 6:45 ` Tian, Kevin
2021-06-28 16:26 ` Jason Gunthorpe
2021-06-24 4:26 ` David Gibson
2021-06-24 5:59 ` Tian, Kevin
2021-06-24 12:22 ` Lu Baolu
2021-06-24 4:23 ` David Gibson
2021-06-18 0:52 ` Jason Gunthorpe
2021-06-18 13:47 ` Joerg Roedel
2021-06-18 15:15 ` Jason Gunthorpe
2021-06-18 15:37 ` Raj, Ashok
2021-06-18 15:51 ` Alex Williamson
2021-06-24 4:29 ` David Gibson
2021-06-24 11:56 ` Jason Gunthorpe
2021-06-18 0:10 ` Jason Gunthorpe
2021-06-17 5:29 ` David Gibson
2021-06-17 5:02 ` David Gibson
2021-06-17 23:04 ` Jason Gunthorpe
2021-06-24 4:37 ` David Gibson
2021-06-24 11:57 ` Jason Gunthorpe
2021-06-10 5:50 ` Lu Baolu [this message]
2021-06-17 5:22 ` David Gibson
2021-06-18 5:21 ` Lu Baolu
2021-06-24 4:03 ` David Gibson
2021-06-24 13:42 ` Lu Baolu
2021-06-17 4:45 ` David Gibson
2021-06-17 23:10 ` Jason Gunthorpe
2021-06-24 4:07 ` David Gibson
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