From: Parav Pandit <parav@nvidia.com>
To: "Cornelia Huck" <cohuck@redhat.com>,
"Daniel P. Berrangé" <berrange@redhat.com>
Cc: "kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"libvir-list@redhat.com" <libvir-list@redhat.com>,
Jason Wang <jasowang@redhat.com>,
"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
Kirti Wankhede <kwankhede@nvidia.com>,
"eauger@redhat.com" <eauger@redhat.com>,
"xin-ran.wang@intel.com" <xin-ran.wang@intel.com>,
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"openstack-discuss@lists.openstack.org"
<openstack-discuss@lists.openstack.org>,
"shaohe.feng@intel.com" <shaohe.feng@intel.com>,
"kevin.tian@intel.com" <kevin.tian@intel.com>,
Yan Zhao <yan.y.zhao@intel.com>,
Parav Pandit <parav@mellanox.com>,
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Alex Williamson <alex.williamson@redhat.com>,
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"intel-gvt-dev@lists.freedesktop.org"
<intel-gvt-dev@lists.freedesktop.org>,
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Jiri Pirko <jiri@mellanox.com>,
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"devel@ovirt.org" <devel@ovirt.org>
Subject: RE: device compatibility interface for live migration with assigned devices
Date: Tue, 18 Aug 2020 09:39:24 +0000 [thread overview]
Message-ID: <BY5PR12MB4322C9D1A66C4657776A1383DC5C0@BY5PR12MB4322.namprd12.prod.outlook.com> (raw)
In-Reply-To: <20200818113652.5d81a392.cohuck@redhat.com>
Hi Cornelia,
> From: Cornelia Huck <cohuck@redhat.com>
> Sent: Tuesday, August 18, 2020 3:07 PM
> To: Daniel P. Berrangé <berrange@redhat.com>
> Cc: Jason Wang <jasowang@redhat.com>; Yan Zhao
> <yan.y.zhao@intel.com>; kvm@vger.kernel.org; libvir-list@redhat.com;
> qemu-devel@nongnu.org; Kirti Wankhede <kwankhede@nvidia.com>;
> eauger@redhat.com; xin-ran.wang@intel.com; corbet@lwn.net; openstack-
> discuss@lists.openstack.org; shaohe.feng@intel.com; kevin.tian@intel.com;
> Parav Pandit <parav@mellanox.com>; jian-feng.ding@intel.com;
> dgilbert@redhat.com; zhenyuw@linux.intel.com; hejie.xu@intel.com;
> bao.yumeng@zte.com.cn; Alex Williamson <alex.williamson@redhat.com>;
> eskultet@redhat.com; smooney@redhat.com; intel-gvt-
> dev@lists.freedesktop.org; Jiri Pirko <jiri@mellanox.com>;
> dinechin@redhat.com; devel@ovirt.org
> Subject: Re: device compatibility interface for live migration with assigned
> devices
>
> On Tue, 18 Aug 2020 10:16:28 +0100
> Daniel P. Berrangé <berrange@redhat.com> wrote:
>
> > On Tue, Aug 18, 2020 at 05:01:51PM +0800, Jason Wang wrote:
> > > On 2020/8/18 下午4:55, Daniel P. Berrangé wrote:
> > >
> > > On Tue, Aug 18, 2020 at 11:24:30AM +0800, Jason Wang wrote:
> > >
> > > On 2020/8/14 下午1:16, Yan Zhao wrote:
> > >
> > > On Thu, Aug 13, 2020 at 12:24:50PM +0800, Jason Wang wrote:
> > >
> > > On 2020/8/10 下午3:46, Yan Zhao wrote:
> >
> > > we actually can also retrieve the same information through sysfs,
> > > .e.g
> > >
> > > |- [path to device]
> > > |--- migration
> > > | |--- self
> > > | | |---device_api
> > > | | |---mdev_type
> > > | | |---software_version
> > > | | |---device_id
> > > | | |---aggregator
> > > | |--- compatible
> > > | | |---device_api
> > > | | |---mdev_type
> > > | | |---software_version
> > > | | |---device_id
> > > | | |---aggregator
> > >
> > >
> > > Yes but:
> > >
> > > - You need one file per attribute (one syscall for one attribute)
> > > - Attribute is coupled with kobject
>
> Is that really that bad? You have the device with an embedded kobject
> anyway, and you can just put things into an attribute group?
>
> [Also, I think that self/compatible split in the example makes things
> needlessly complex. Shouldn't semantic versioning and matching already
> cover nearly everything? I would expect very few cases that are more
> complex than that. Maybe the aggregation stuff, but I don't think we need
> that self/compatible split for that, either.]
>
> > >
> > > All of above seems unnecessary.
> > >
> > > Another point, as we discussed in another thread, it's really hard
> > > to make sure the above API work for all types of devices and
> > > frameworks. So having a vendor specific API looks much better.
> > >
> > > From the POV of userspace mgmt apps doing device compat checking /
> > > migration, we certainly do NOT want to use different vendor
> > > specific APIs. We want to have an API that can be used / controlled in a
> standard manner across vendors.
> > >
> > > Yes, but it could be hard. E.g vDPA will chose to use devlink (there's a
> > > long debate on sysfs vs devlink). So if we go with sysfs, at least two
> > > APIs needs to be supported ...
> >
> > NB, I was not questioning devlink vs sysfs directly. If devlink is
> > related to netlink, I can't say I'm enthusiastic as IMKE sysfs is
> > easier to deal with. I don't know enough about devlink to have much of an
> opinion though.
> > The key point was that I don't want the userspace APIs we need to deal
> > with to be vendor specific.
>
> From what I've seen of devlink, it seems quite nice; but I understand why
> sysfs might be easier to deal with (especially as there's likely already a lot of
> code using it.)
>
> I understand that some users would like devlink because it is already widely
> used for network drivers (and some others), but I don't think the majority of
> devices used with vfio are network (although certainly a lot of them are.)
>
> >
> > What I care about is that we have a *standard* userspace API for
> > performing device compatibility checking / state migration, for use by
> > QEMU/libvirt/ OpenStack, such that we can write code without countless
> > vendor specific code paths.
> >
> > If there is vendor specific stuff on the side, that's fine as we can
> > ignore that, but the core functionality for device compat / migration
> > needs to be standardized.
>
> To summarize:
> - choose one of sysfs or devlink
> - have a common interface, with a standardized way to add
> vendor-specific attributes
> ?
Please refer to my previous email which has more example and details.
next prev parent reply other threads:[~2020-08-18 13:41 UTC|newest]
Thread overview: 118+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-13 23:29 device compatibility interface for live migration with assigned devices Yan Zhao
2020-07-14 10:21 ` Daniel P. Berrangé
2020-07-14 12:33 ` Sean Mooney
[not found] ` <20200714110148.0471c03c@x1.home>
[not found] ` <eb705c72cdc8b6b8959b6ebaeeac6069a718d524.camel@redhat.com>
2020-07-14 21:15 ` Sean Mooney
2020-07-14 16:16 ` Alex Williamson
2020-07-14 16:47 ` Daniel P. Berrangé
2020-07-14 20:47 ` Alex Williamson
2020-07-15 9:16 ` Daniel P. Berrangé
2020-07-14 17:19 ` Dr. David Alan Gilbert
2020-07-14 20:59 ` Alex Williamson
2020-07-15 7:37 ` Alex Xu
2020-07-17 15:18 ` Alex Williamson
2020-07-15 8:20 ` Yan Zhao
2020-07-15 8:49 ` Feng, Shaohe
2020-07-15 9:21 ` Alex Xu
2020-07-17 14:59 ` Alex Williamson
2020-07-17 18:03 ` Dr. David Alan Gilbert
2020-07-17 18:30 ` Alex Williamson
2020-07-15 8:23 ` Dr. David Alan Gilbert
2020-07-15 7:23 ` Alex Xu
2020-07-16 4:16 ` Jason Wang
2020-07-16 8:32 ` Yan Zhao
2020-07-16 9:30 ` Jason Wang
2020-07-17 16:12 ` Alex Williamson
2020-07-20 3:41 ` Jason Wang
2020-07-20 10:39 ` Sean Mooney
2020-07-21 2:11 ` Jason Wang
2020-07-21 0:51 ` Yan Zhao
2020-07-27 7:24 ` Yan Zhao
2020-07-27 22:23 ` Alex Williamson
2020-07-29 8:05 ` Yan Zhao
2020-07-29 11:28 ` Sean Mooney
2020-07-29 19:12 ` Alex Williamson
2020-07-30 3:41 ` Yan Zhao
2020-07-30 13:24 ` Sean Mooney
2020-07-30 17:29 ` Alex Williamson
2020-08-04 8:37 ` Yan Zhao
2020-08-05 9:44 ` Dr. David Alan Gilbert
2020-07-30 1:56 ` Yan Zhao
2020-07-30 13:14 ` Sean Mooney
2020-08-04 16:35 ` Cornelia Huck
2020-08-05 2:22 ` Jason Wang
2020-08-05 2:16 ` Yan Zhao
2020-08-05 2:41 ` Jason Wang
2020-08-05 7:56 ` Jiri Pirko
2020-08-05 8:02 ` Jason Wang
2020-08-05 9:33 ` Yan Zhao
2020-08-05 10:53 ` Jiri Pirko
2020-08-05 11:35 ` Sean Mooney
2020-08-07 11:59 ` Cornelia Huck
2020-08-13 15:33 ` Cornelia Huck
2020-08-13 19:02 ` Eric Farman
2020-08-17 6:38 ` Cornelia Huck
2020-08-10 7:46 ` Yan Zhao
2020-08-13 4:24 ` Jason Wang
2020-08-14 5:16 ` Yan Zhao
2020-08-14 12:30 ` Sean Mooney
2020-08-17 1:52 ` Yan Zhao
2020-08-18 3:24 ` Jason Wang
2020-08-18 8:55 ` Daniel P. Berrangé
2020-08-18 9:06 ` Cornelia Huck
2020-08-18 9:24 ` Daniel P. Berrangé
2020-08-18 9:38 ` Cornelia Huck
[not found] ` <3a073222-dcfe-c02d-198b-29f6a507b2e1@redhat.com>
2020-08-18 9:16 ` Daniel P. Berrangé
2020-08-18 9:36 ` Cornelia Huck
2020-08-18 9:39 ` Parav Pandit [this message]
2020-08-19 3:30 ` Yan Zhao
2020-08-19 5:58 ` Parav Pandit
2020-08-19 9:41 ` Jason Wang
2020-08-19 6:57 ` [ovirt-devel] " Jason Wang
2020-08-19 6:59 ` Yan Zhao
2020-08-19 7:39 ` Jason Wang
2020-08-19 8:13 ` Yan Zhao
2020-08-19 9:28 ` Jason Wang
2020-08-20 12:27 ` Cornelia Huck
2020-08-21 3:14 ` Jason Wang
2020-08-21 14:52 ` Cornelia Huck
2020-08-31 3:07 ` Jason Wang
2020-08-19 17:50 ` Alex Williamson
2020-08-20 0:18 ` Yan Zhao
2020-08-20 3:13 ` Alex Williamson
2020-08-20 3:09 ` Yan Zhao
2020-08-19 2:54 ` Jason Wang
2020-08-20 0:39 ` Yan Zhao
2020-08-20 1:29 ` Sean Mooney
2020-08-20 4:01 ` Yan Zhao
2020-08-20 5:16 ` Sean Mooney
2020-08-20 6:27 ` Yan Zhao
2020-08-20 13:24 ` Sean Mooney
2020-08-26 8:54 ` Yan Zhao
2020-08-20 3:22 ` Alex Williamson
2020-08-20 3:16 ` Yan Zhao
2020-08-25 14:39 ` Cornelia Huck
2020-08-26 6:41 ` Yan Zhao
2020-08-28 13:47 ` Cornelia Huck
2020-08-28 14:04 ` Sean Mooney
2020-08-31 4:43 ` Yan Zhao
2020-09-08 14:41 ` Cornelia Huck
2020-09-09 2:13 ` Yan Zhao
2020-09-10 12:38 ` Cornelia Huck
2020-09-10 12:50 ` Sean Mooney
2020-09-10 18:02 ` Alex Williamson
2020-09-11 0:56 ` Yan Zhao
2020-09-11 10:08 ` Cornelia Huck
2020-09-11 10:18 ` Tian, Kevin
2020-09-11 16:51 ` Alex Williamson
2020-09-14 13:48 ` Zeng, Xin
2020-09-14 14:44 ` Alex Williamson
2020-09-15 7:46 ` Zeng, Xin
2020-09-09 5:37 ` Yan Zhao
2020-08-31 2:23 ` Yan Zhao
2020-08-19 2:38 ` Jason Wang
2020-08-18 9:32 ` Parav Pandit
2020-08-19 2:45 ` Jason Wang
2020-08-19 5:26 ` Parav Pandit
2020-08-19 6:48 ` Jason Wang
2020-08-19 6:53 ` Parav Pandit
2020-07-29 19:05 ` Dr. David Alan Gilbert
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