Fwd: [virtio-comment] Re: [virtio-dev] Re: [virtio-comment] [PATCH v3 1/1] virtio-ism: introduce new device virtio-ism

[Alexandra Winter <wintera@linux.ibm.com>]

Forwarding to virtio-comment@lists.oasis-open.org for completeness
as I cannot post to virtio-dev@lists.oasis-open.org


-------- Forwarded Message --------
Subject: [virtio-comment] Re: [virtio-dev] Re: [virtio-comment] [PATCH v3 1/1] virtio-ism: introduce new device virtio-ism
Date: Wed, 5 Apr 2023 15:02:57 +0200
From: Alexandra Winter <wintera@linux.ibm.com>
To: Michael S. Tsirkin <mst@redhat.com>
CC: Wen Gu <guwen@linux.alibaba.com>, Halil Pasic <pasic@linux.ibm.com>, Xuan Zhuo <xuanzhuo@linux.alibaba.com>, virtio-comment@lists.oasis-open.org, hans@linux.alibaba.com, herongguang@linux.alibaba.com, zmlcc@linux.alibaba.com, dust.li@linux.alibaba.com, tonylu@linux.alibaba.com, zhenzao@linux.alibaba.com, helinguo@linux.alibaba.com, gerry@linux.alibaba.com, cohuck@redhat.com, jasowang@redhat.com, Jan Kiszka <jan.kiszka@siemens.com>, kgraul@linux.ibm.com, wenjia@linux.ibm.com, jaka@linux.ibm.com, hca@linux.ibm.com, twinkler@linux.ibm.com, raspl@linux.ibm.com, virtio-dev@lists.oasis-open.org



On 05.04.23 14:52, Michael S. Tsirkin wrote:
> On Wed, Apr 05, 2023 at 02:39:53PM +0200, Alexandra Winter wrote:
>>
>>
>> On 24.03.23 05:03, Wen Gu wrote:
>>>
>>>
>>> On 2023/3/23 22:46, Halil Pasic wrote:
>>>
>>>> On Thu, 9 Feb 2023 11:30:56 +0800
>>>> Xuan Zhuo <xuanzhuo@linux.alibaba.com> wrote:
>>>>
>>
>> ...
>>
>>>
>>>> To get back to the things proposed here: the cdid is IMHO
>>>> a nice thing, and is functionally corresponding to the
>>>> (S)EID. But it is 16 byte wide, and I have no idea how
>>>> is it supposed to be used in the CLC handshake.
>>>>
>>>
>>> CLC handshake carry one SEID for all the SMC-D device. Considering
>>> coexistence with ISM, I am not sure whether we can change or increase
>>> the SEID.. cc Alexandra
>>>
>>> Thanks!
>>> Wen Gu
>>
>> As mentioned by others, discussions are ongoing.
>> It would be great, if we can agree on a way to use the existing CLC handshake
>> for SMC-D via virtio-ism and ism-loopback.
>> In that case SEID needs to be unique per hardware instance, cannot be increased and
>> can only be changed for x86 in a non-colliding way.
>>
>> An alternative would be to define new a SMC-D(?) protocol variant/version, where we
>> are free to define new fields (e.g. UUIDs).
>>
>> Alexandra
> 
> Problem with tying to hardware is that it is blocking
> migration (which is a challenge with ism anyway, but still).

Very true. My assumption is that _Internal_ Shared Memory
is limited to one instance of HW (as it is today).
So the 2 partners need to be on the same instance of HW.
So after migration of 1 partner, they should be able to detect
that internal SMC-D is no longer possible and switch to
SMC-R (remote) for the next connection.
(I have no idea how a connection could survive migration) 

> 
> 
>>>
>>>> If this is really supposed to work with SMC and not just take
>>>> inspiration from it, I would like some insight from our
>>>> SMC experts (they are already on copy).
>>>>
>>>> Regards,
>>>> Halil
>>>>
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> 

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