From: Jason Gunthorpe <jgg@nvidia.com>
To: Alex Williamson <alex.williamson@redhat.com>
Cc: "Tian, Kevin" <kevin.tian@intel.com>,
Jean-Philippe Brucker <jean-philippe@linaro.org>,
"Jiang, Dave" <dave.jiang@intel.com>,
"Raj, Ashok" <ashok.raj@intel.com>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
Jonathan Corbet <corbet@lwn.net>,
Robin Murphy <robin.murphy@arm.com>,
LKML <linux-kernel@vger.kernel.org>,
"iommu@lists.linux-foundation.org"
<iommu@lists.linux-foundation.org>,
David Gibson <david@gibson.dropbear.id.au>,
Kirti Wankhede <kwankhede@nvidia.com>,
David Woodhouse <dwmw2@infradead.org>,
Jason Wang <jasowang@redhat.com>
Subject: Re: [RFC] /dev/ioasid uAPI proposal
Date: Thu, 3 Jun 2021 17:10:18 -0300 [thread overview]
Message-ID: <20210603201018.GF1002214@nvidia.com> (raw)
In-Reply-To: <20210603140146.5ce4f08a.alex.williamson@redhat.com>
On Thu, Jun 03, 2021 at 02:01:46PM -0600, Alex Williamson wrote:
> > > > 1) Mixing IOMMU_CAP_CACHE_COHERENCY and !IOMMU_CAP_CACHE_COHERENCY
> > > > domains.
> > > >
> > > > This doesn't actually matter. If you mix them together then kvm
> > > > will turn on wbinvd anyhow, so we don't need to use the DMA_PTE_SNP
> > > > anywhere in this VM.
> > > >
> > > > This if two IOMMU's are joined together into a single /dev/ioasid
> > > > then we can just make them both pretend to be
> > > > !IOMMU_CAP_CACHE_COHERENCY and both not set IOMMU_CACHE.
> > >
> > > Yes and no. Yes, if any domain is !IOMMU_CAP_CACHE_COHERENCY then we
> > > need to emulate wbinvd, but no we'll use IOMMU_CACHE any time it's
> > > available based on the per domain support available. That gives us the
> > > most consistent behavior, ie. we don't have VMs emulating wbinvd
> > > because they used to have a device attached where the domain required
> > > it and we can't atomically remap with new flags to perform the same as
> > > a VM that never had that device attached in the first place.
> >
> > I think we are saying the same thing..
>
> Hrm? I think I'm saying the opposite of your "both not set
> IOMMU_CACHE". IOMMU_CACHE is the mapping flag that enables
> DMA_PTE_SNP. Maybe you're using IOMMU_CACHE as the state reported to
> KVM?
I'm saying if we enable wbinvd in the guest then no IOASIDs used by
that guest need to set DMA_PTE_SNP. If we disable wbinvd in the guest
then all IOASIDs must enforce DMA_PTE_SNP (or we otherwise guarentee
no-snoop is not possible).
This is not what VFIO does today, but it is a reasonable choice.
Based on that observation we can say as soon as the user wants to use
an IOMMU that does not support DMA_PTE_SNP in the guest we can still
share the IO page table with IOMMUs that do support DMA_PTE_SNP.
> > It doesn't solve the problem to connect kvm to AP and kvmgt though
>
> It does not, we'll probably need a vfio ioctl to gratuitously announce
> the KVM fd to each device. I think some devices might currently fail
> their open callback if that linkage isn't already available though, so
> it's not clear when that should happen, ie. it can't currently be a
> VFIO_DEVICE ioctl as getting the device fd requires an open, but this
> proposal requires some availability of the vfio device fd without any
> setup, so presumably that won't yet call the driver open callback.
> Maybe that's part of the attach phase now... I'm not sure, it's not
> clear when the vfio device uAPI starts being available in the process
> of setting up the ioasid. Thanks,
At a certain point we maybe just have to stick to backward compat, I
think. Though it is useful to think about green field alternates to
try to guide the backward compat design..
Jason
next prev parent reply other threads:[~2021-06-03 20:10 UTC|newest]
Thread overview: 258+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-27 7:58 [RFC] /dev/ioasid uAPI proposal Tian, Kevin
2021-05-28 2:24 ` Jason Wang
2021-05-28 20:25 ` Jason Gunthorpe
[not found] ` <20210531164118.265789ee@yiliu-dev>
2021-06-01 2:36 ` Jason Wang
2021-06-01 4:27 ` Shenming Lu
2021-06-01 5:10 ` Jason Wang
[not found] ` <20210601113152.6d09e47b@yiliu-dev>
2021-06-01 5:08 ` Jason Wang
2021-06-01 5:23 ` Lu Baolu
2021-06-01 5:29 ` Jason Wang
2021-06-01 5:42 ` Tian, Kevin
2021-06-01 6:07 ` Jason Wang
2021-06-01 6:16 ` Tian, Kevin
2021-06-01 8:47 ` Jason Wang
2021-06-01 17:31 ` Jason Gunthorpe
2021-06-02 8:54 ` Jason Wang
2021-06-02 17:21 ` Jason Gunthorpe
2021-06-07 13:30 ` Enrico Weigelt, metux IT consult
2021-06-07 18:01 ` Jason Gunthorpe
2021-06-08 10:45 ` Enrico Weigelt, metux IT consult
2021-06-10 2:16 ` Jason Wang
2021-06-08 1:10 ` Jason Wang
2021-06-08 13:20 ` Jason Gunthorpe
2021-06-10 2:00 ` Jason Wang
2021-06-10 4:03 ` Jason Wang
2021-06-10 11:47 ` Jason Gunthorpe
2021-06-11 5:43 ` Jason Wang
2021-06-01 17:29 ` Jason Gunthorpe
2021-06-02 8:58 ` Jason Wang
2021-05-28 16:23 ` Jean-Philippe Brucker
2021-05-28 20:16 ` Jason Gunthorpe
2021-06-01 7:50 ` Tian, Kevin
2021-05-28 17:35 ` Jason Gunthorpe
2021-06-01 8:10 ` Tian, Kevin
2021-06-01 17:42 ` Jason Gunthorpe
2021-06-02 1:33 ` Tian, Kevin
2021-06-02 16:09 ` Jason Gunthorpe
2021-06-03 1:29 ` Tian, Kevin
2021-06-03 5:09 ` David Gibson
2021-06-03 6:49 ` Tian, Kevin
2021-06-03 11:47 ` Jason Gunthorpe
2021-06-04 2:15 ` Tian, Kevin
2021-06-08 0:49 ` David Gibson
2021-06-09 2:52 ` Tian, Kevin
2021-06-02 6:32 ` David Gibson
2021-06-02 16:16 ` Jason Gunthorpe
2021-06-03 2:11 ` Tian, Kevin
2021-06-03 5:13 ` David Gibson
2021-06-03 11:52 ` Jason Gunthorpe
2021-06-08 0:53 ` David Gibson
2021-06-08 19:04 ` Jason Gunthorpe
2021-06-17 2:42 ` David Gibson
2021-05-28 19:58 ` Jason Gunthorpe
2021-06-01 8:38 ` Tian, Kevin
2021-06-01 17:56 ` Jason Gunthorpe
2021-06-02 2:00 ` Tian, Kevin
2021-06-02 6:57 ` David Gibson
2021-06-02 16:37 ` Jason Gunthorpe
2021-06-03 5:23 ` David Gibson
2021-06-03 12:28 ` Jason Gunthorpe
2021-06-08 6:04 ` David Gibson
2021-06-08 19:23 ` Jason Gunthorpe
2021-06-02 6:48 ` David Gibson
2021-06-02 16:58 ` Jason Gunthorpe
2021-06-03 2:49 ` Tian, Kevin
2021-06-03 5:48 ` David Gibson
2021-06-03 5:45 ` David Gibson
2021-06-03 12:11 ` Jason Gunthorpe
2021-06-04 6:08 ` Tian, Kevin
2021-06-04 12:33 ` Jason Gunthorpe
2021-06-04 23:20 ` Tian, Kevin
2021-06-08 6:13 ` David Gibson
2021-06-04 10:24 ` Jean-Philippe Brucker
2021-06-04 12:05 ` Jason Gunthorpe
2021-06-04 17:27 ` Jacob Pan
2021-06-04 17:40 ` Jason Gunthorpe
2021-06-08 6:31 ` David Gibson
2021-06-10 16:37 ` Jean-Philippe Brucker
2021-06-17 3:00 ` David Gibson
2021-06-18 17:03 ` Jean-Philippe Brucker
2021-06-18 18:30 ` Jason Gunthorpe
2021-06-23 8:19 ` Tian, Kevin
2021-06-23 7:57 ` Tian, Kevin
2021-06-24 3:49 ` David Gibson
2021-05-28 20:03 ` Jason Gunthorpe
2021-06-01 7:01 ` Tian, Kevin
2021-06-01 20:28 ` Jason Gunthorpe
2021-06-02 1:25 ` Tian, Kevin
2021-06-02 23:27 ` Jason Gunthorpe
2021-06-04 8:17 ` Jean-Philippe Brucker
2021-06-04 8:43 ` Tian, Kevin
2021-06-02 8:52 ` Jason Wang
2021-06-02 16:07 ` Jason Gunthorpe
2021-06-01 22:22 ` Alex Williamson
2021-06-02 2:20 ` Tian, Kevin
2021-06-02 16:01 ` Jason Gunthorpe
2021-06-02 17:11 ` Alex Williamson
2021-06-02 17:35 ` Jason Gunthorpe
2021-06-02 18:01 ` Alex Williamson
2021-06-02 18:09 ` Jason Gunthorpe
2021-06-02 19:00 ` Alex Williamson
2021-06-02 19:54 ` Jason Gunthorpe
2021-06-02 20:37 ` Alex Williamson
2021-06-02 22:45 ` Jason Gunthorpe
2021-06-03 2:50 ` Alex Williamson
2021-06-03 3:22 ` Tian, Kevin
2021-06-03 4:14 ` Alex Williamson
2021-06-03 5:18 ` Tian, Kevin
2021-06-03 12:40 ` Jason Gunthorpe
2021-06-03 20:41 ` Alex Williamson
2021-06-04 9:19 ` Tian, Kevin
2021-06-04 15:37 ` Alex Williamson
2021-06-04 12:13 ` Jason Gunthorpe
2021-06-04 21:45 ` Alex Williamson
2021-06-04 7:33 ` Tian, Kevin
2021-06-03 12:34 ` Jason Gunthorpe
2021-06-03 20:01 ` Alex Williamson
2021-06-03 20:10 ` Jason Gunthorpe [this message]
2021-06-03 21:44 ` Alex Williamson
2021-06-04 8:38 ` Tian, Kevin
2021-06-04 12:28 ` Jason Gunthorpe
2021-06-04 15:26 ` Alex Williamson
2021-06-04 15:40 ` Paolo Bonzini
2021-06-04 15:50 ` Jason Gunthorpe
2021-06-04 15:57 ` Paolo Bonzini
2021-06-04 16:03 ` Jason Gunthorpe
2021-06-04 16:10 ` Paolo Bonzini
2021-06-04 17:22 ` Jason Gunthorpe
2021-06-04 21:29 ` Alex Williamson
2021-06-04 23:01 ` Jason Gunthorpe
2021-06-07 15:41 ` Alex Williamson
2021-06-07 18:18 ` Jason Gunthorpe
2021-06-07 18:59 ` Alex Williamson
2021-06-07 19:08 ` Jason Gunthorpe
2021-06-07 19:41 ` Alex Williamson
2021-06-07 23:03 ` Jason Gunthorpe
2021-06-08 0:30 ` Alex Williamson
2021-06-08 1:20 ` Jason Wang
2021-06-30 6:53 ` Christoph Hellwig
2021-06-30 6:49 ` Christoph Hellwig
2021-06-07 3:25 ` Tian, Kevin
2021-06-07 6:51 ` Paolo Bonzini
2021-06-07 18:01 ` Jason Gunthorpe
2021-06-30 6:56 ` Christoph Hellwig
2021-06-05 6:22 ` Paolo Bonzini
2021-06-07 3:50 ` Tian, Kevin
2021-06-07 17:59 ` Jason Gunthorpe
2021-06-08 7:56 ` Paolo Bonzini
2021-06-08 13:15 ` Jason Gunthorpe
2021-06-08 13:44 ` Paolo Bonzini
2021-06-08 18:47 ` Alex Williamson
2021-06-08 19:00 ` Jason Gunthorpe
2021-06-09 8:51 ` Enrico Weigelt, metux IT consult
2021-06-09 9:11 ` Paolo Bonzini
2021-06-09 11:54 ` Jason Gunthorpe
2021-06-09 14:31 ` Alex Williamson
2021-06-09 14:45 ` Jason Gunthorpe
2021-06-09 15:20 ` Paolo Bonzini
2021-10-27 6:18 ` Tian, Kevin
2021-10-27 10:32 ` Paolo Bonzini
2021-10-28 1:50 ` Tian, Kevin
2021-06-09 2:49 ` Tian, Kevin
2021-06-09 11:57 ` Jason Gunthorpe
2021-06-09 12:46 ` Paolo Bonzini
2021-06-09 12:47 ` Jason Gunthorpe
2021-06-09 13:24 ` Paolo Bonzini
2021-06-09 14:32 ` Jason Gunthorpe
2021-06-30 7:01 ` Christoph Hellwig
2021-06-09 18:09 ` Alex Williamson
2021-06-03 2:52 ` Jason Wang
2021-06-03 13:09 ` Jason Gunthorpe
2021-06-04 1:11 ` Jason Wang
2021-06-04 11:58 ` Jason Gunthorpe
2021-06-07 3:18 ` Jason Wang
2021-06-07 14:14 ` Jason Gunthorpe
2021-06-08 1:00 ` Jason Wang
2021-06-08 8:54 ` Enrico Weigelt, metux IT consult
2021-06-08 12:52 ` Jason Gunthorpe
2021-06-30 7:07 ` Christoph Hellwig
2021-06-30 7:05 ` Christoph Hellwig
2021-06-08 2:37 ` David Gibson
2021-06-08 13:17 ` Jason Gunthorpe
2021-06-17 3:47 ` David Gibson
2021-06-23 7:59 ` Tian, Kevin
2021-06-24 3:53 ` David Gibson
2021-05-28 23:36 ` Jason Gunthorpe
2021-05-31 11:31 ` Liu Yi L
2021-05-31 18:09 ` Jason Gunthorpe
2021-06-01 3:08 ` Lu Baolu
2021-06-01 17:24 ` Jason Gunthorpe
2021-06-01 1:25 ` Lu Baolu
2021-06-01 11:09 ` Lu Baolu
2021-06-01 17:26 ` Jason Gunthorpe
2021-06-02 4:01 ` Lu Baolu
2021-06-02 23:23 ` Jason Gunthorpe
2021-06-03 5:49 ` Lu Baolu
2021-06-03 5:54 ` David Gibson
2021-06-03 6:50 ` Lu Baolu
2021-06-03 12:56 ` Jason Gunthorpe
2021-06-02 7:22 ` David Gibson
2021-06-03 6:39 ` Tian, Kevin
2021-06-03 13:05 ` Jason Gunthorpe
2021-06-04 6:37 ` Tian, Kevin
2021-06-04 12:09 ` Jason Gunthorpe
2021-06-04 23:10 ` Tian, Kevin
2021-06-07 17:54 ` Jason Gunthorpe
2021-06-15 8:59 ` Tian, Kevin
2021-06-15 15:06 ` Jason Gunthorpe
2021-06-15 22:59 ` Tian, Kevin
2021-06-15 23:02 ` Jason Gunthorpe
2021-06-15 23:09 ` Tian, Kevin
2021-06-15 23:40 ` Jason Gunthorpe
2021-06-15 23:56 ` Tian, Kevin
2021-06-15 23:59 ` Jason Gunthorpe
2021-06-16 0:02 ` Tian, Kevin
2021-05-31 17:37 ` Parav Pandit
2021-05-31 18:12 ` Jason Gunthorpe
2021-06-01 12:04 ` Parav Pandit
2021-06-01 17:36 ` Jason Gunthorpe
2021-06-02 8:38 ` Enrico Weigelt, metux IT consult
2021-06-02 12:41 ` Parav Pandit
2021-06-01 4:31 ` Shenming Lu
2021-06-01 5:10 ` Lu Baolu
2021-06-01 7:15 ` Shenming Lu
2021-06-01 12:30 ` Lu Baolu
2021-06-01 13:10 ` Shenming Lu
2021-06-01 17:33 ` Jason Gunthorpe
2021-06-02 4:50 ` Shenming Lu
2021-06-03 18:19 ` Jacob Pan
2021-06-04 1:30 ` Jason Wang
2021-06-04 16:22 ` Jacob Pan
2021-06-04 16:22 ` Jason Gunthorpe
2021-06-04 18:05 ` Jacob Pan
2021-06-04 2:03 ` Shenming Lu
2021-06-07 12:19 ` Liu, Yi L
2021-06-08 1:09 ` Shenming Lu
2021-06-01 17:30 ` Parav Pandit
2021-06-03 20:58 ` Jacob Pan
2021-06-08 6:30 ` Parav Pandit
2021-06-02 6:15 ` David Gibson
2021-06-02 17:19 ` Jason Gunthorpe
2021-06-03 3:02 ` Tian, Kevin
2021-06-03 6:26 ` David Gibson
2021-06-03 12:46 ` Jason Gunthorpe
2021-06-04 6:27 ` Tian, Kevin
2021-06-03 7:17 ` Tian, Kevin
2021-06-03 12:49 ` Jason Gunthorpe
2021-06-08 5:49 ` David Gibson
2021-06-03 8:12 ` Tian, Kevin
2021-06-17 4:07 ` David Gibson
2021-06-23 8:00 ` Tian, Kevin
2021-06-24 3:55 ` David Gibson
2021-06-02 8:56 ` Enrico Weigelt, metux IT consult
2021-06-02 17:24 ` Jason Gunthorpe
2021-06-04 10:44 ` Enrico Weigelt, metux IT consult
2021-06-04 12:30 ` Jason Gunthorpe
2021-06-08 1:15 ` David Gibson
2021-06-08 10:43 ` Enrico Weigelt, metux IT consult
2021-06-08 13:11 ` Jason Gunthorpe
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