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

[Xuan Zhuo <xuanzhuo@linux.alibaba.com>]

On Wed, 5 Apr 2023 15:06:38 +0200, Alexandra Winter <wintera@linux.ibm.com> wrote:
> 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)


I agree.

In terms of structure, there is no way to support migration. We can indeed
provide some means to perceive the occurrence of migration to the upper
users. Finally, the user (such as SMC) decides how to do it by itself.

Thanks.


>
> >
> >
> >>>
> >>>> 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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