From: Eric Auger <eric.auger@redhat.com>
To: Jason Gunthorpe <jgg@nvidia.com>,
Alex Williamson <alex.williamson@redhat.com>
Cc: Lu Baolu <baolu.lu@linux.intel.com>,
Chaitanya Kulkarni <chaitanyak@nvidia.com>,
Cornelia Huck <cohuck@redhat.com>,
Daniel Jordan <daniel.m.jordan@oracle.com>,
David Gibson <david@gibson.dropbear.id.au>,
iommu@lists.linux-foundation.org,
Jason Wang <jasowang@redhat.com>,
Jean-Philippe Brucker <jean-philippe@linaro.org>,
Joao Martins <joao.m.martins@oracle.com>,
Kevin Tian <kevin.tian@intel.com>,
kvm@vger.kernel.org, Matthew Rosato <mjrosato@linux.ibm.com>,
"Michael S. Tsirkin" <mst@redhat.com>,
Nicolin Chen <nicolinc@nvidia.com>,
Niklas Schnelle <schnelle@linux.ibm.com>,
Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>,
Yi Liu <yi.l.liu@intel.com>, Keqian Zhu <zhukeqian1@huawei.com>
Subject: Re: [PATCH RFC 11/12] iommufd: vfio container FD ioctl compatibility
Date: Thu, 24 Mar 2022 09:13:17 +0100 [thread overview]
Message-ID: <09a6557f-b881-081c-abdf-266516f7b0eb@redhat.com> (raw)
In-Reply-To: <20220324003342.GV11336@nvidia.com>
Hi,
On 3/24/22 1:33 AM, Jason Gunthorpe wrote:
> On Wed, Mar 23, 2022 at 04:51:25PM -0600, Alex Williamson wrote:
>
>> My overall question here would be whether we can actually achieve a
>> compatibility interface that has sufficient feature transparency that we
>> can dump vfio code in favor of this interface, or will there be enough
>> niche use cases that we need to keep type1 and vfio containers around
>> through a deprecation process?
> Other than SPAPR, I think we can.
>
>> The locked memory differences for one seem like something that
>> libvirt wouldn't want hidden
> I'm first interested to have an understanding how this change becomes
> a real problem in practice that requires libvirt to do something
> different for vfio or iommufd. We can discuss in the other thread
>
> If this is the make or break point then I think we can deal with it
> either by going back to what vfio does now or perhaps some other
> friendly compat approach..
>
>> and we have questions regarding support for vaddr hijacking
> I'm not sure what vaddr hijacking is? Do you mean
> VFIO_DMA_MAP_FLAG_VADDR ? There is a comment that outlines my plan to
> implement it in a functionally compatible way without the deadlock
> problem. I estimate this as a small project.
>
>> and different ideas how to implement dirty page tracking,
> I don't think this is compatibility. No kernel today triggers qemu to
> use this feature as no kernel supports live migration. No existing
> qemu will trigger this feature with new kernels that support live
> migration v2. Therefore we can adjust qemu's dirty tracking at the
> same time we enable migration v2 in qemu.
>
> With Joao's work we are close to having a solid RFC to come with
> something that can be fully implemented.
>
> Hopefully we can agree to this soon enough that qemu can come with a
> full package of migration v2 support including the dirty tracking
> solution.
>
>> not to mention the missing features that are currently well used,
>> like p2p mappings, coherency tracking, mdev, etc.
> I consider these all mandatory things, they won't be left out.
>
> The reason they are not in the RFC is mostly because supporting them
> requires work outside just this iommufd area, and I'd like this series
> to remain self-contained.
>
> I've already got a draft to add DMABUF support to VFIO PCI which
> nicely solves the follow_pfn security problem, we want to do this for
> another reason already. I'm waiting for some testing feedback before
> posting it. Need some help from Daniel make the DMABUF revoke semantic
> him and I have been talking about. In the worst case can copy the
> follow_pfn approach.
>
> Intel no-snoop is simple enough, just needs some Intel cleanup parts.
>
> mdev will come along with the final VFIO integration, all the really
> hard parts are done already. The VFIO integration is a medium sized
> task overall.
>
> So, I'm not ready to give up yet :)
>
>> Where do we focus attention? Is symlinking device files our proposal
>> to userspace and is that something achievable, or do we want to use
>> this compatibility interface as a means to test the interface and
>> allow userspace to make use of it for transition, if their use cases
>> allow it, perhaps eventually performing the symlink after deprecation
>> and eventual removal of the vfio container and type1 code? Thanks,
> symlinking device files is definitely just a suggested way to expedite
> testing.
>
> Things like qemu that are learning to use iommufd-only features should
> learn to directly open iommufd instead of vfio container to activate
> those features.
>
> Looking long down the road I don't think we want to have type 1 and
> iommufd code forever. So, I would like to make an option to compile
> out vfio container support entirely and have that option arrange for
> iommufd to provide the container device node itself.
I am currently working on migrating the QEMU VFIO device onto the new
API because since after our discussions the compat mode cannot be used
anyway to implemented nesting. I hope I will be able to present
something next week.
Thanks
Eric
>
> I think we can get there pretty quickly, or at least I haven't got
> anything that is scaring me alot (beyond SPAPR of course)
>
> For the dpdk/etcs of the world I think we are already there.
>
> Jason
>
next prev parent reply other threads:[~2022-03-24 8:13 UTC|newest]
Thread overview: 122+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-18 17:27 [PATCH RFC 00/12] IOMMUFD Generic interface Jason Gunthorpe
2022-03-18 17:27 ` [PATCH RFC 01/12] interval-tree: Add a utility to iterate over spans in an interval tree Jason Gunthorpe
2022-03-18 17:27 ` [PATCH RFC 02/12] iommufd: Overview documentation Jason Gunthorpe
2022-03-18 17:27 ` [PATCH RFC 03/12] iommufd: File descriptor, context, kconfig and makefiles Jason Gunthorpe
2022-03-22 14:18 ` Niklas Schnelle
2022-03-22 14:50 ` Jason Gunthorpe
2022-03-18 17:27 ` [PATCH RFC 04/12] kernel/user: Allow user::locked_vm to be usable for iommufd Jason Gunthorpe
2022-03-22 14:28 ` Niklas Schnelle
2022-03-22 14:57 ` Jason Gunthorpe
2022-03-22 15:29 ` Alex Williamson
2022-03-22 16:15 ` Jason Gunthorpe
2022-03-24 2:11 ` Tian, Kevin
2022-03-24 2:27 ` Jason Wang
2022-03-24 2:42 ` Tian, Kevin
2022-03-24 2:57 ` Jason Wang
2022-03-24 3:15 ` Tian, Kevin
2022-03-24 3:50 ` Jason Wang
2022-03-24 4:29 ` Tian, Kevin
2022-03-24 11:46 ` Jason Gunthorpe
2022-03-28 1:53 ` Jason Wang
2022-03-28 12:22 ` Jason Gunthorpe
2022-03-29 4:59 ` Jason Wang
2022-03-29 11:46 ` Jason Gunthorpe
2022-03-28 13:14 ` Sean Mooney
2022-03-28 14:27 ` Jason Gunthorpe
2022-03-24 20:40 ` Alex Williamson
2022-03-24 22:27 ` Jason Gunthorpe
2022-03-24 22:41 ` Alex Williamson
2022-03-22 16:31 ` Niklas Schnelle
2022-03-22 16:41 ` Jason Gunthorpe
2022-03-18 17:27 ` [PATCH RFC 05/12] iommufd: PFN handling for iopt_pages Jason Gunthorpe
2022-03-23 15:37 ` Niklas Schnelle
2022-03-23 16:09 ` Jason Gunthorpe
2022-03-18 17:27 ` [PATCH RFC 06/12] iommufd: Algorithms for PFN storage Jason Gunthorpe
2022-03-18 17:27 ` [PATCH RFC 07/12] iommufd: Data structure to provide IOVA to PFN mapping Jason Gunthorpe
2022-03-22 22:15 ` Alex Williamson
2022-03-23 18:15 ` Jason Gunthorpe
2022-03-24 3:09 ` Tian, Kevin
2022-03-24 12:46 ` Jason Gunthorpe
2022-03-25 13:34 ` zhangfei.gao
2022-03-25 17:19 ` Jason Gunthorpe
2022-04-13 14:02 ` Yi Liu
2022-04-13 14:36 ` Jason Gunthorpe
2022-04-13 14:49 ` Yi Liu
2022-04-17 14:56 ` Yi Liu
2022-04-18 10:47 ` Yi Liu
2022-03-18 17:27 ` [PATCH RFC 08/12] iommufd: IOCTLs for the io_pagetable Jason Gunthorpe
2022-03-23 19:10 ` Alex Williamson
2022-03-23 19:34 ` Jason Gunthorpe
2022-03-23 20:04 ` Alex Williamson
2022-03-23 20:34 ` Jason Gunthorpe
2022-03-23 22:54 ` Jason Gunthorpe
2022-03-24 7:25 ` Tian, Kevin
2022-03-24 13:46 ` Jason Gunthorpe
2022-03-25 2:15 ` Tian, Kevin
2022-03-27 2:32 ` Tian, Kevin
2022-03-27 14:28 ` Jason Gunthorpe
2022-03-28 17:17 ` Alex Williamson
2022-03-28 18:57 ` Jason Gunthorpe
2022-03-28 19:47 ` Jason Gunthorpe
2022-03-28 21:26 ` Alex Williamson
2022-03-24 6:46 ` Tian, Kevin
2022-03-30 13:35 ` Yi Liu
2022-03-31 12:59 ` Jason Gunthorpe
2022-04-01 13:30 ` Yi Liu
2022-03-31 4:36 ` David Gibson
2022-03-31 5:41 ` Tian, Kevin
2022-03-31 12:58 ` Jason Gunthorpe
2022-04-28 5:58 ` David Gibson
2022-04-28 14:22 ` Jason Gunthorpe
2022-04-29 6:00 ` David Gibson
2022-04-29 12:54 ` Jason Gunthorpe
2022-04-30 14:44 ` David Gibson
2022-03-18 17:27 ` [PATCH RFC 09/12] iommufd: Add a HW pagetable object Jason Gunthorpe
2022-03-18 17:27 ` [PATCH RFC 10/12] iommufd: Add kAPI toward external drivers Jason Gunthorpe
2022-03-23 18:10 ` Alex Williamson
2022-03-23 18:15 ` Jason Gunthorpe
2022-05-11 12:54 ` Yi Liu
2022-05-19 9:45 ` Yi Liu
2022-05-19 12:35 ` Jason Gunthorpe
2022-03-18 17:27 ` [PATCH RFC 11/12] iommufd: vfio container FD ioctl compatibility Jason Gunthorpe
2022-03-23 22:51 ` Alex Williamson
2022-03-24 0:33 ` Jason Gunthorpe
2022-03-24 8:13 ` Eric Auger [this message]
2022-03-24 22:04 ` Alex Williamson
2022-03-24 23:11 ` Jason Gunthorpe
2022-03-25 3:10 ` Tian, Kevin
2022-03-25 11:24 ` Joao Martins
2022-04-28 14:53 ` David Gibson
2022-04-28 15:10 ` Jason Gunthorpe
2022-04-29 1:21 ` Tian, Kevin
2022-04-29 6:22 ` David Gibson
2022-04-29 12:50 ` Jason Gunthorpe
2022-05-02 4:10 ` David Gibson
2022-04-29 6:20 ` David Gibson
2022-04-29 12:48 ` Jason Gunthorpe
2022-05-02 7:30 ` David Gibson
2022-05-05 19:07 ` Jason Gunthorpe
2022-05-06 5:25 ` David Gibson
2022-05-06 10:42 ` Tian, Kevin
2022-05-09 3:36 ` David Gibson
2022-05-06 12:48 ` Jason Gunthorpe
2022-05-09 6:01 ` David Gibson
2022-05-09 14:00 ` Jason Gunthorpe
2022-05-10 7:12 ` David Gibson
2022-05-10 19:00 ` Jason Gunthorpe
2022-05-11 3:15 ` Tian, Kevin
2022-05-11 16:32 ` Jason Gunthorpe
2022-05-11 23:23 ` Tian, Kevin
2022-05-13 4:35 ` David Gibson
2022-05-11 4:40 ` David Gibson
2022-05-11 2:46 ` Tian, Kevin
2022-05-23 6:02 ` Alexey Kardashevskiy
2022-05-24 13:25 ` Jason Gunthorpe
2022-05-25 1:39 ` David Gibson
2022-05-25 2:09 ` Alexey Kardashevskiy
2022-03-29 9:17 ` Yi Liu
2022-03-18 17:27 ` [PATCH RFC 12/12] iommufd: Add a selftest Jason Gunthorpe
2022-04-12 20:13 ` [PATCH RFC 00/12] IOMMUFD Generic interface Eric Auger
2022-04-12 20:22 ` Jason Gunthorpe
2022-04-12 20:50 ` Eric Auger
2022-04-14 10:56 ` Yi Liu
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