Re: [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 Mon, 10 Apr 2023 09:23:04 +0800, Jason Wang <jasowang@redhat.com> wrote:
> On Fri, Apr 7, 2023 at 11:24âAM Xuan Zhuo <xuanzhuo@linux.alibaba.com> wrote:
> >
> > On Wed, 5 Apr 2023 08:52:14 -0400, "Michael S. Tsirkin" <mst@redhat.com> 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).
> >
> >
> > We don't want to support migration. At least we don't want to support it for the
> > time being. Because there are indeed many problems. I think Migration is not
> > necessary for a new Virtio device.
>
> We'd really need to take migration into consideration when developing
> new devices. It is not guaranteed that this device is backed by local
> RAMs.

Yes, we have some considerations and researches on the aspects also, such as
CXL.

We have not planned introducing these in SPEC directly, because we dont even
have a POC. It's just that there are researches in this area and we haven't
actually operated it.

> At least we should avoid designs that may complicate future
> migration support.

Yes, we try to avoid it. If you find that we have this problem, you are welcome
to point out.

Thanks.


>
> Thanks
>
> >
> > 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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