From: David Gibson <david@gibson.dropbear.id.au>
To: Jason Gunthorpe <jgg@nvidia.com>
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>,
"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, 24 Jun 2021 14:29:29 +1000 [thread overview]
Message-ID: <YNQKKSb3onBCz+f6@yekko> (raw)
In-Reply-To: <20210618151506.GG1002214@nvidia.com>
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On Fri, Jun 18, 2021 at 12:15:06PM -0300, Jason Gunthorpe wrote:
> On Fri, Jun 18, 2021 at 03:47:51PM +0200, Joerg Roedel wrote:
> > Hi Kevin,
> >
> > On Thu, Jun 17, 2021 at 07:31:03AM +0000, Tian, Kevin wrote:
> > > Now let's talk about the new IOMMU behavior:
> > >
> > > - A device is blocked from doing DMA to any resource outside of
> > > its group when it's probed by the IOMMU driver. This could be a
> > > special state w/o attaching to any domain, or a new special domain
> > > type which differentiates it from existing domain types (identity,
> > > dma, or unmanged). Actually existing code already includes a
> > > IOMMU_DOMAIN_BLOCKED type but nobody uses it.
> >
> > There is a reason for the default domain to exist: Devices which require
> > RMRR mappings to be present. You can't just block all DMA from devices
> > until a driver takes over, we put much effort into making sure there is
> > not even a small window in time where RMRR regions (unity mapped regions
> > on AMD) are not mapped.
>
> Yes, I think the DMA blocking can only start around/after a VFIO type
> driver has probed() and bound to a device in the group, not much
> different from today.
But as I keep saying, some forms of grouping (and DMA aliasing as Alex
mentioned) mean that changing the domain of one device can change the
domain of another device, unavoidably. It may be rare with modern
hardware, but we still can't ignore the case.
Which means you can't DMA block until everything in the group is
managed by a vfio-like driver.
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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_______________________________________________
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WARNING: multiple messages have this Message-ID (diff)
From: David Gibson <david@gibson.dropbear.id.au>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: Joerg Roedel <joro@8bytes.org>,
"Tian, Kevin" <kevin.tian@intel.com>,
Alex Williamson <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, 24 Jun 2021 14:29:29 +1000 [thread overview]
Message-ID: <YNQKKSb3onBCz+f6@yekko> (raw)
In-Reply-To: <20210618151506.GG1002214@nvidia.com>
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On Fri, Jun 18, 2021 at 12:15:06PM -0300, Jason Gunthorpe wrote:
> On Fri, Jun 18, 2021 at 03:47:51PM +0200, Joerg Roedel wrote:
> > Hi Kevin,
> >
> > On Thu, Jun 17, 2021 at 07:31:03AM +0000, Tian, Kevin wrote:
> > > Now let's talk about the new IOMMU behavior:
> > >
> > > - A device is blocked from doing DMA to any resource outside of
> > > its group when it's probed by the IOMMU driver. This could be a
> > > special state w/o attaching to any domain, or a new special domain
> > > type which differentiates it from existing domain types (identity,
> > > dma, or unmanged). Actually existing code already includes a
> > > IOMMU_DOMAIN_BLOCKED type but nobody uses it.
> >
> > There is a reason for the default domain to exist: Devices which require
> > RMRR mappings to be present. You can't just block all DMA from devices
> > until a driver takes over, we put much effort into making sure there is
> > not even a small window in time where RMRR regions (unity mapped regions
> > on AMD) are not mapped.
>
> Yes, I think the DMA blocking can only start around/after a VFIO type
> driver has probed() and bound to a device in the group, not much
> different from today.
But as I keep saying, some forms of grouping (and DMA aliasing as Alex
mentioned) mean that changing the domain of one device can change the
domain of another device, unavoidably. It may be rare with modern
hardware, but we still can't ignore the case.
Which means you can't DMA block until everything in the group is
managed by a vfio-like driver.
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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next prev parent reply other threads:[~2021-06-24 4:52 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 [this message]
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
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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