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Subject: Re: [virtio-dev] [PATCH v2 1/1] virtio-ism: introduce new device virtio-ism
On Fri, 13 Jan 2023 10:29:49 +0800, Jason Wang <jasowang@redhat.com> wrote: > On Fri, Jan 13, 2023 at 9:59 AM Xuan Zhuo <xuanzhuo@linux.alibaba.com> wrote: > > > > On Thu, 12 Jan 2023 16:41:32 +0100, Halil Pasic <pasic@linux.ibm.com> wrote: > > > On Thu, 12 Jan 2023 15:30:58 +0100 > > > Cornelia Huck <cohuck@redhat.com> wrote: > > > > > > > >> > > > > >> I like that: we don't want to talk about hosts/VMMs/etc. as we > > > > >> fundamentally deal with devices and drivers, but sharing between guests > > > > >> is of course the obvious use case. > > > > >> > > > > >> I'm just wondering how best to express the uniqueness scope, is it per > > > > >> (ISM) device? > > > > > > > > > > No, each vm has at least one separate device. The devices in a host form > > > > > an uniqueness scope. > > > > > > > > Should we call it a 'group', then? A host would be an example of such a > > > > group. > > > > > > How about 'communication domain'? Devices within a single communication > > > domain may be able to speak to each other via SMC and may not have the > > > same device_id. Two devices from different communication domains can't > > > communicate via ISM, but may have the same device_id. > > > > I agree. > > > > > > > > I don't like group because it is very generic, and may sound like > > > the grouping can be done arbitrarily. E.g. with a shared memory based > > > implementation akin to the PoC putting devices on different hosts into > > > the same 'group' should be illegal. > > Any reason why this is illegal? The ism device must on the same host. > > > > > > > On the other hand there is also the following question. If we move away > > > form the one ID per host model ("The device MUST ensure that the gid on > > > the same entity i same and different from the gid on other entity.") then > > > we could also allow having more than one communication domains on a > > > single host (to limit what entities can use ISM to communicate). > > Yes, but I think it might not be necessary to say how gid is actually > implemented, I can think most of the time it should be provisioned by > the the management stack which is probably out of the scope of the > spec. Imagine that the VMs from two different cloud manufacturers may have the same GID (Host-Id). They believed that they can communicate based on ISM Device. This is wrong. Thanks. > > Thanks > > > > > Yes, this is a good idea. > > > > Thanks. > > > > > > > > Regards, > > > Halil > > > > > >
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