From: Alex Williamson <alex.williamson@redhat.com>
To: Joerg Roedel <joro@8bytes.org>
Cc: Jason Gunthorpe <jgg@nvidia.com>,
"Tian, Kevin" <kevin.tian@intel.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>,
Lu Baolu <baolu.lu@linux.intel.com>
Subject: Re: Plan for /dev/ioasid RFC v2
Date: Wed, 9 Jun 2021 10:27:22 -0600 [thread overview]
Message-ID: <20210609102722.5abf62e1.alex.williamson@redhat.com> (raw)
In-Reply-To: <20210609101532.452851eb.alex.williamson@redhat.com>
On Wed, 9 Jun 2021 10:15:32 -0600
Alex Williamson <alex.williamson@redhat.com> wrote:
> On Wed, 9 Jun 2021 17:51:26 +0200
> Joerg Roedel <joro@8bytes.org> wrote:
>
> > On Wed, Jun 09, 2021 at 12:00:09PM -0300, Jason Gunthorpe wrote:
> > > Only *drivers* know what the actual device is going to do, devices do
> > > not. Since the group doesn't have drivers it is the wrong layer to be
> > > making choices about how to configure the IOMMU.
> >
> > Groups don't carry how to configure IOMMUs, that information is
> > mostly in the IOMMU domains. And those (or an abstraction of them) is
> > configured through /dev/ioasid. So not sure what you wanted to say with
> > the above.
> >
> > All a group carries is information about which devices are not
> > sufficiently isolated from each other and thus need to always be in the
> > same domain.
> >
> > > The device centric approach is my attempt at this, and it is pretty
> > > clean, I think.
> >
> > Clean, but still insecure.
> >
> > > All ACS does is prevent P2P operations, if you assign all the group
> > > devices into the same /dev/iommu then you may not care about that
> > > security isolation property. At the very least it is policy for user
> > > to decide, not kernel.
> >
> > It is a kernel decision, because a fundamental task of the kernel is to
> > ensure isolation between user-space tasks as good as it can. And if a
> > device assigned to one task can interfer with a device of another task
> > (e.g. by sending P2P messages), then the promise of isolation is broken.
>
> AIUI, the IOASID model will still enforce IOMMU groups, but it's not an
> explicit part of the interface like it is for vfio. For example the
> IOASID model allows attaching individual devices such that we have
> granularity to create per device IOASIDs, but all devices within an
> IOMMU group are required to be attached to an IOASID before they can be
> used. It's not entirely clear to me yet how that last bit gets
> implemented though, ie. what barrier is in place to prevent device
> usage prior to reaching this viable state.
>
> > > Groups should be primarily about isolation security, not about IOASID
> > > matching.
> >
> > That doesn't make any sense, what do you mean by 'IOASID matching'?
>
> One of the problems with the vfio interface use of groups is that we
> conflate the IOMMU group for both isolation and granularity. I think
> what Jason is referring to here is that we still want groups to be the
> basis of isolation, but we don't want a uAPI that presumes all devices
> within the group must use the same IOASID. For example, if a user owns
> an IOMMU group consisting of non-isolated functions of a multi-function
> device, they should be able to create a vIOMMU VM where each of those
> functions has its own address space. That can't be done today, the
> entire group would need to be attached to the VM under a PCIe-to-PCI
> bridge to reflect the address space limitation imposed by the vfio
> group uAPI model. Thanks,
Hmm, likely discussed previously in these threads, but I can't come up
with the argument that prevents us from making the BIND interface
at the group level but the ATTACH interface at the device level? For
example:
- VFIO_GROUP_BIND_IOASID_FD
- VFIO_DEVICE_ATTACH_IOASID
AFAICT that makes the group ownership more explicit but still allows
the device level IOASID granularity. Logically this is just an
internal iommu_group_for_each_dev() in the BIND ioctl. Thanks,
Alex
next prev parent reply other threads:[~2021-06-09 16:27 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 [this message]
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
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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