From: Jason Gunthorpe <jgg@nvidia.com>
To: David Gibson <david@gibson.dropbear.id.au>
Cc: Joerg Roedel <joro@8bytes.org>,
"Tian, Kevin" <kevin.tian@intel.com>,
"Alex Williamson (alex.williamson@redhat.com)"
<alex.williamson@redhat.com>,
Jean-Philippe Brucker <jean-philippe@linaro.org>,
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: Thu, 17 Jun 2021 20:10:04 -0300 [thread overview]
Message-ID: <20210617231004.GA1002214@nvidia.com> (raw)
In-Reply-To: <YMrTeuUoqgzmSplL@yekko>
On Thu, Jun 17, 2021 at 02:45:46PM +1000, David Gibson wrote:
> On Wed, Jun 09, 2021 at 09:39:19AM -0300, 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
>
> mdev drivers might know these, but shim drivers, like basic vfio-pci
> often won't.
The generic drivers say 'I will do every kind of DMA possible', which
is in-of-itself a special kind of information to convey.
There are alot of weird corners to think about here, like what if the
guest asks for a PASID on a mdev that doesn't support PASID, but
hooked to a RID that does or other quite nonsense combinations. These
need to be blocked/handled/whatever properly, which is made much
easier if the common code actually knows detail about what is going
on.
> I still think you're having a tendency to partially conflate several
> meanings of "group":
> 1. the unavoidable hardware unit of non-isolation
> 2. the kernel internal concept and interface to it
> 3. the user visible fd and interface
I think I have those pretty clearly seperated :)
> We can't avoid having (1) somewhere, (3) and to a lesser extent (2)
> are what you object to.
I don't like (3) either, and am yet to hear a definitive reason why we
must have it..
> > The current approach has the group try to guess the device driver
> > intention in the vfio type 1 code.
>
> I agree this has gotten ugly. What I'm not yet convinced of is that
> reworking groups to make this not-ugly necessarily requires totally
> minimizing the importance of groups.
I think it does - we can't have the group in the middle and still put
the driver in chrage, it doesn't really work.
At least if someone can see an arrangement otherwise lets hear it -
start with how to keep groups and remove the mdev hackery from type1..
Jason
WARNING: multiple messages have this Message-ID (diff)
From: Jason Gunthorpe <jgg@nvidia.com>
To: David Gibson <david@gibson.dropbear.id.au>
Cc: "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
Jason Wang <jasowang@redhat.com>,
Kirti Wankhede <kwankhede@nvidia.com>,
Jean-Philippe Brucker <jean-philippe@linaro.org>,
"Jiang, Dave" <dave.jiang@intel.com>,
"Raj, Ashok" <ashok.raj@intel.com>,
Jonathan Corbet <corbet@lwn.net>,
"Tian, Kevin" <kevin.tian@intel.com>,
"parav@mellanox.com" <parav@mellanox.com>,
"Alex Williamson \(alex.williamson@redhat.com\)"
<alex.williamson@redhat.com>,
"Enrico Weigelt, metux IT consult" <lkml@metux.net>,
Robin Murphy <robin.murphy@arm.com>,
LKML <linux-kernel@vger.kernel.org>,
Shenming Lu <lushenming@huawei.com>,
"iommu@lists.linux-foundation.org"
<iommu@lists.linux-foundation.org>,
Paolo Bonzini <pbonzini@redhat.com>,
David Woodhouse <dwmw2@infradead.org>
Subject: Re: Plan for /dev/ioasid RFC v2
Date: Thu, 17 Jun 2021 20:10:04 -0300 [thread overview]
Message-ID: <20210617231004.GA1002214@nvidia.com> (raw)
In-Reply-To: <YMrTeuUoqgzmSplL@yekko>
On Thu, Jun 17, 2021 at 02:45:46PM +1000, David Gibson wrote:
> On Wed, Jun 09, 2021 at 09:39:19AM -0300, 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
>
> mdev drivers might know these, but shim drivers, like basic vfio-pci
> often won't.
The generic drivers say 'I will do every kind of DMA possible', which
is in-of-itself a special kind of information to convey.
There are alot of weird corners to think about here, like what if the
guest asks for a PASID on a mdev that doesn't support PASID, but
hooked to a RID that does or other quite nonsense combinations. These
need to be blocked/handled/whatever properly, which is made much
easier if the common code actually knows detail about what is going
on.
> I still think you're having a tendency to partially conflate several
> meanings of "group":
> 1. the unavoidable hardware unit of non-isolation
> 2. the kernel internal concept and interface to it
> 3. the user visible fd and interface
I think I have those pretty clearly seperated :)
> We can't avoid having (1) somewhere, (3) and to a lesser extent (2)
> are what you object to.
I don't like (3) either, and am yet to hear a definitive reason why we
must have it..
> > The current approach has the group try to guess the device driver
> > intention in the vfio type 1 code.
>
> I agree this has gotten ugly. What I'm not yet convinced of is that
> reworking groups to make this not-ugly necessarily requires totally
> minimizing the importance of groups.
I think it does - we can't have the group in the middle and still put
the driver in chrage, it doesn't really work.
At least if someone can see an arrangement otherwise lets hear it -
start with how to keep groups and remove the mdev hackery from type1..
Jason
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu
next prev parent reply other threads:[~2021-06-17 23:10 UTC|newest]
Thread overview: 162+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-07 2:58 Plan for /dev/ioasid RFC v2 Tian, Kevin
2021-06-07 2:58 ` Tian, Kevin
2021-06-09 8:14 ` Eric Auger
2021-06-09 8:14 ` Eric Auger
2021-06-09 9:37 ` Tian, Kevin
2021-06-09 9:37 ` Tian, Kevin
2021-06-09 10:14 ` Eric Auger
2021-06-09 10:14 ` Eric Auger
2021-06-09 9:01 ` Leon Romanovsky
2021-06-09 9:01 ` Leon Romanovsky
2021-06-09 9:43 ` Tian, Kevin
2021-06-09 9:43 ` Tian, Kevin
2021-06-09 12:24 ` Joerg Roedel
2021-06-09 12:24 ` Joerg Roedel
2021-06-09 12:39 ` Jason Gunthorpe
2021-06-09 12:39 ` Jason Gunthorpe
2021-06-09 13:32 ` Joerg Roedel
2021-06-09 13:32 ` Joerg Roedel
2021-06-09 15:00 ` Jason Gunthorpe
2021-06-09 15:00 ` Jason Gunthorpe
2021-06-09 15:51 ` Joerg Roedel
2021-06-09 15:51 ` Joerg Roedel
2021-06-09 16:15 ` Alex Williamson
2021-06-09 16:15 ` Alex Williamson
2021-06-09 16:27 ` Alex Williamson
2021-06-09 16:27 ` Alex Williamson
2021-06-09 18:49 ` Jason Gunthorpe
2021-06-09 18:49 ` Jason Gunthorpe
2021-06-10 15:38 ` Alex Williamson
2021-06-10 15:38 ` Alex Williamson
2021-06-11 0:58 ` Tian, Kevin
2021-06-11 0:58 ` Tian, Kevin
2021-06-11 21:38 ` Alex Williamson
2021-06-11 21:38 ` Alex Williamson
2021-06-14 3:09 ` Tian, Kevin
2021-06-14 3:09 ` Tian, Kevin
2021-06-14 3:22 ` Alex Williamson
2021-06-14 3:22 ` Alex Williamson
2021-06-15 1:05 ` Tian, Kevin
2021-06-15 1:05 ` Tian, Kevin
2021-06-14 13:38 ` Jason Gunthorpe
2021-06-14 13:38 ` Jason Gunthorpe
2021-06-15 1:21 ` Tian, Kevin
2021-06-15 1:21 ` Tian, Kevin
2021-06-15 16:56 ` Alex Williamson
2021-06-15 16:56 ` Alex Williamson
2021-06-16 6:53 ` Tian, Kevin
2021-06-16 6:53 ` Tian, Kevin
2021-06-24 4:50 ` David Gibson
2021-06-24 4:50 ` David Gibson
2021-06-11 16:45 ` Jason Gunthorpe
2021-06-11 16:45 ` Jason Gunthorpe
2021-06-11 19:38 ` Alex Williamson
2021-06-11 19:38 ` Alex Williamson
2021-06-12 1:28 ` Jason Gunthorpe
2021-06-12 1:28 ` Jason Gunthorpe
2021-06-12 16:57 ` Alex Williamson
2021-06-12 16:57 ` Alex Williamson
2021-06-14 14:07 ` Jason Gunthorpe
2021-06-14 14:07 ` Jason Gunthorpe
2021-06-14 16:28 ` Alex Williamson
2021-06-14 16:28 ` Alex Williamson
2021-06-14 19:40 ` Jason Gunthorpe
2021-06-14 19:40 ` Jason Gunthorpe
2021-06-15 2:31 ` Tian, Kevin
2021-06-15 2:31 ` Tian, Kevin
2021-06-15 16:12 ` Alex Williamson
2021-06-15 16:12 ` Alex Williamson
2021-06-16 6:43 ` Tian, Kevin
2021-06-16 6:43 ` Tian, Kevin
2021-06-16 19:39 ` Alex Williamson
2021-06-16 19:39 ` Alex Williamson
2021-06-17 3:39 ` Liu Yi L
2021-06-17 3:39 ` Liu Yi L
2021-06-17 7:31 ` Tian, Kevin
2021-06-17 7:31 ` Tian, Kevin
2021-06-17 21:14 ` Alex Williamson
2021-06-17 21:14 ` Alex Williamson
2021-06-18 0:19 ` Jason Gunthorpe
2021-06-18 0:19 ` Jason Gunthorpe
2021-06-18 16:57 ` Tian, Kevin
2021-06-18 16:57 ` Tian, Kevin
2021-06-18 18:23 ` Jason Gunthorpe
2021-06-18 18:23 ` Jason Gunthorpe
2021-06-25 10:27 ` Tian, Kevin
2021-06-25 10:27 ` Tian, Kevin
2021-06-25 14:36 ` Jason Gunthorpe
2021-06-25 14:36 ` Jason Gunthorpe
2021-06-28 1:09 ` Tian, Kevin
2021-06-28 1:09 ` Tian, Kevin
2021-06-28 22:31 ` Alex Williamson
2021-06-28 22:31 ` Alex Williamson
2021-06-28 22:48 ` Jason Gunthorpe
2021-06-28 22:48 ` Jason Gunthorpe
2021-06-28 23:09 ` Alex Williamson
2021-06-28 23:09 ` Alex Williamson
2021-06-28 23:13 ` Jason Gunthorpe
2021-06-28 23:13 ` Jason Gunthorpe
2021-06-29 0:26 ` Tian, Kevin
2021-06-29 0:26 ` Tian, Kevin
2021-06-29 0:28 ` Tian, Kevin
2021-06-29 0:28 ` Tian, Kevin
2021-06-29 0:43 ` Tian, Kevin
2021-06-29 0:43 ` Tian, Kevin
2021-06-28 2:03 ` Tian, Kevin
2021-06-28 2:03 ` Tian, Kevin
2021-06-28 14:41 ` Jason Gunthorpe
2021-06-28 14:41 ` Jason Gunthorpe
2021-06-28 6:45 ` Tian, Kevin
2021-06-28 6:45 ` Tian, Kevin
2021-06-28 16:26 ` Jason Gunthorpe
2021-06-28 16:26 ` Jason Gunthorpe
2021-06-24 4:26 ` David Gibson
2021-06-24 4:26 ` David Gibson
2021-06-24 5:59 ` Tian, Kevin
2021-06-24 5:59 ` Tian, Kevin
2021-06-24 12:22 ` Lu Baolu
2021-06-24 12:22 ` Lu Baolu
2021-06-24 4:23 ` David Gibson
2021-06-24 4:23 ` David Gibson
2021-06-18 0:52 ` Jason Gunthorpe
2021-06-18 0:52 ` Jason Gunthorpe
2021-06-18 13:47 ` Joerg Roedel
2021-06-18 13:47 ` Joerg Roedel
2021-06-18 15:15 ` Jason Gunthorpe
2021-06-18 15:15 ` Jason Gunthorpe
2021-06-18 15:37 ` Raj, Ashok
2021-06-18 15:37 ` Raj, Ashok
2021-06-18 15:51 ` Alex Williamson
2021-06-18 15:51 ` Alex Williamson
2021-06-24 4:29 ` David Gibson
2021-06-24 4:29 ` David Gibson
2021-06-24 11:56 ` Jason Gunthorpe
2021-06-24 11:56 ` Jason Gunthorpe
2021-06-18 0:10 ` Jason Gunthorpe
2021-06-18 0:10 ` Jason Gunthorpe
2021-06-17 5:29 ` David Gibson
2021-06-17 5:29 ` David Gibson
2021-06-17 5:02 ` David Gibson
2021-06-17 5:02 ` David Gibson
2021-06-17 23:04 ` Jason Gunthorpe
2021-06-17 23:04 ` Jason Gunthorpe
2021-06-24 4:37 ` David Gibson
2021-06-24 4:37 ` David Gibson
2021-06-24 11:57 ` Jason Gunthorpe
2021-06-24 11:57 ` Jason Gunthorpe
2021-06-10 5:50 ` Lu Baolu
2021-06-10 5:50 ` Lu Baolu
2021-06-17 5:22 ` David Gibson
2021-06-17 5:22 ` David Gibson
2021-06-18 5:21 ` Lu Baolu
2021-06-18 5:21 ` Lu Baolu
2021-06-24 4:03 ` David Gibson
2021-06-24 4:03 ` David Gibson
2021-06-24 13:42 ` Lu Baolu
2021-06-24 13:42 ` Lu Baolu
2021-06-17 4:45 ` David Gibson
2021-06-17 4:45 ` David Gibson
2021-06-17 23:10 ` Jason Gunthorpe [this message]
2021-06-17 23:10 ` Jason Gunthorpe
2021-06-24 4:07 ` David Gibson
2021-06-24 4:07 ` David Gibson
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