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From: Jason Wang <jasowang@redhat.com>
To: Cornelia Huck <cohuck@redhat.com>
Cc: "Yan Zhao" <yan.y.zhao@intel.com>,
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	"devel@ovirt.org" <devel@ovirt.org>
Subject: Re: [ovirt-devel] Re: device compatibility interface for live migration with assigned devices
Date: Mon, 31 Aug 2020 11:07:53 +0800	[thread overview]
Message-ID: <b9739032-9bc0-ec48-a4c7-36c055b91702@redhat.com> (raw)
In-Reply-To: <20200821165255.53e26628.cohuck@redhat.com>


On 2020/8/21 下午10:52, Cornelia Huck wrote:
> On Fri, 21 Aug 2020 11:14:41 +0800
> Jason Wang <jasowang@redhat.com> wrote:
>
>> On 2020/8/20 下午8:27, Cornelia Huck wrote:
>>> On Wed, 19 Aug 2020 17:28:38 +0800
>>> Jason Wang <jasowang@redhat.com> wrote:
>>>   
>>>> On 2020/8/19 下午4:13, Yan Zhao wrote:
>>>>> On Wed, Aug 19, 2020 at 03:39:50PM +0800, Jason Wang wrote:
>>>>>> On 2020/8/19 下午2:59, Yan Zhao wrote:
>>>>>>> On Wed, Aug 19, 2020 at 02:57:34PM +0800, Jason Wang wrote:
>>>>>>>> On 2020/8/19 上午11:30, Yan Zhao wrote:
>>>>>>>>> hi All,
>>>>>>>>> could we decide that sysfs is the interface that every VFIO vendor driver
>>>>>>>>> needs to provide in order to support vfio live migration, otherwise the
>>>>>>>>> userspace management tool would not list the device into the compatible
>>>>>>>>> list?
>>>>>>>>>
>>>>>>>>> if that's true, let's move to the standardizing of the sysfs interface.
>>>>>>>>> (1) content
>>>>>>>>> common part: (must)
>>>>>>>>>         - software_version: (in major.minor.bugfix scheme)
>>>>>>>> This can not work for devices whose features can be negotiated/advertised
>>>>>>>> independently. (E.g virtio devices)
>>> I thought the 'software_version' was supposed to describe kind of a
>>> 'protocol version' for the data we transmit? I.e., you add a new field,
>>> you bump the version number.
>>
>> Ok, but since we mandate backward compatibility of uABI, is this really
>> worth to have a version for sysfs? (Searching on sysfs shows no examples
>> like this)
> I was not thinking about the sysfs interface, but rather about the data
> that is sent over while migrating. E.g. we find out that sending some
> auxiliary data is a good idea and bump to version 1.1.0; version 1.0.0
> cannot deal with the extra data, but version 1.1.0 can deal with the
> older data stream.
>
> (...)


Well, I think what data to transmit during migration is the duty of qemu 
not kernel. And I suspect the idea of reading opaque data (with version) 
from kernel and transmit them to dest is the best approach.


>
>>>>>>>>>         - device_api: vfio-pci or vfio-ccw ...
>>>>>>>>>         - type: mdev type for mdev device or
>>>>>>>>>                 a signature for physical device which is a counterpart for
>>>>>>>>> 	   mdev type.
>>>>>>>>>
>>>>>>>>> device api specific part: (must)
>>>>>>>>>        - pci id: pci id of mdev parent device or pci id of physical pci
>>>>>>>>>          device (device_api is vfio-pci)API here.
>>>>>>>> So this assumes a PCI device which is probably not true.
>>>>>>>>      
>>>>>>> for device_api of vfio-pci, why it's not true?
>>>>>>>
>>>>>>> for vfio-ccw, it's subchannel_type.
>>>>>> Ok but having two different attributes for the same file is not good idea.
>>>>>> How mgmt know there will be a 3rd type?
>>>>> that's why some attributes need to be common. e.g.
>>>>> device_api: it's common because mgmt need to know it's a pci device or a
>>>>>                ccw device. and the api type is already defined vfio.h.
>>>>> 	    (The field is agreed by and actually suggested by Alex in previous mail)
>>>>> type: mdev_type for mdev. if mgmt does not understand it, it would not
>>>>>          be able to create one compatible mdev device.
>>>>> software_version: mgmt can compare the major and minor if it understands
>>>>>          this fields.
>>>> I think it would be helpful if you can describe how mgmt is expected to
>>>> work step by step with the proposed sysfs API. This can help people to
>>>> understand.
>>> My proposal would be:
>>> - check that device_api matches
>>> - check possible device_api specific attributes
>>> - check that type matches [I don't think the combination of mdev types
>>>     and another attribute to determine compatibility is a good idea;
>>
>> Any reason for this? Actually if we only use mdev type to detect the
>> compatibility, it would be much more easier. Otherwise, we are actually
>> re-inventing mdev types.
>>
>> E.g can we have the same mdev types with different device_api and other
>> attributes?
> In the end, the mdev type is represented as a string; but I'm not sure
> we can expect that two types with the same name, but a different
> device_api are related in any way.
>
> If we e.g. compare vfio-pci and vfio-ccw, they are fundamentally
> different.
>
> I was mostly concerned about the aggregation proposal, where type A +
> aggregation value b might be compatible with type B + aggregation value
> a.


Yes, that looks pretty complicated.


>
>>
>>>     actually, the current proposal confuses me every time I look at it]
>>> - check that software_version is compatible, assuming semantic
>>>     versioning
>>> - check possible type-specific attributes
>>
>> I'm not sure if this is too complicated. And I suspect there will be
>> vendor specific attributes:
>>
>> - for compatibility check: I think we should either modeling everything
>> via mdev type or making it totally vendor specific. Having something in
>> the middle will bring a lot of burden
> FWIW, I'm for a strict match on mdev type, and flexibility in per-type
> attributes.


I'm not sure whether the above flexibility can work better than encoding 
them to mdev type. If we really want ultra flexibility, we need making 
the compatibility check totally vendor specific.


>
>> - for provisioning: it's still not clear. As shown in this proposal, for
>> NVME we may need to set remote_url, but unless there will be a subclass
>> (NVME) in the mdev (which I guess not), we can't prevent vendor from
>> using another attribute name, in this case, tricks like attributes
>> iteration in some sub directory won't work. So even if we had some
>> common API for compatibility check, the provisioning API is still vendor
>> specific ...
> Yes, I'm not sure how to deal with the "same thing for different
> vendors" problem. We can try to make sure that in-kernel drivers play
> nicely, but not much more.


Then it's actually a subclass of mdev I guess in the future.

Thanks



  reply	other threads:[~2020-08-31  3:08 UTC|newest]

Thread overview: 114+ 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  8:20         ` Yan Zhao
2020-07-15  8:49           ` Feng, Shaohe
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
     [not found]         ` <CAH7mGatPWsczh_rbVhx4a+psJXvkZgKou3r5HrEQTqE7SqZkKA@mail.gmail.com>
2020-07-17 15:18           ` Alex Williamson
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
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 [this message]
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
2020-09-09  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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