On Fri, Oct 21, 2022 at 1:13 PM Tony Lu <[email protected]> wrote: > > On Fri, Oct 21, 2022 at 12:54:22PM +0800, Dust Li wrote: > > On Fri, Oct 21, 2022 at 11:53:10AM +0800, Tony Lu wrote: > > >On Fri, Oct 21, 2022 at 11:09:19AM +0800, Jason Wang wrote: > > >> On Fri, Oct 21, 2022 at 11:05 AM Tony Lu <[email protected]> > > >> wrote: > > >> > > > >> > On Fri, Oct 21, 2022 at 10:47:29AM +0800, Jason Wang wrote: > > >> > > On Wed, Oct 19, 2022 at 6:01 PM Tony Lu <[email protected]> > > >> > > wrote: > > >> > > > > > >> > > > On Wed, Oct 19, 2022 at 05:04:58PM +0800, Jason Wang wrote: > > >> > > > > > > >> > > > > 在 2022/10/19 16:07, Tony Lu 写道: > > >> > > > > > On Wed, Oct 19, 2022 at 02:02:21PM +0800, Xuan Zhuo wrote: > > >> > > > > > > On Wed, 19 Oct 2022 12:36:35 +0800, Jason Wang > > >> > > > > > > <[email protected]> wrote: > > >> > > > > > > > On Wed, Oct 19, 2022 at 12:22 PM Xuan Zhuo > > >> > > > > > > > <[email protected]> wrote: > > >> > > > > > > > > On Wed, 19 Oct 2022 11:56:52 +0800, Jason Wang > > >> > > > > > > > > <[email protected]> wrote: > > >> > > > > > > > > > On Wed, Oct 19, 2022 at 10:42 AM Xuan Zhuo > > >> > > > > > > > > > <[email protected]> wrote: > > >> > > > > > > > > > > On Mon, 17 Oct 2022 16:17:31 +0800, Jason Wang > > >> > > > > > > > > > > <[email protected]> wrote: > > >> > > > > > > > > > > > > >> > > > > > > > > > > > > >> > > > > > > > > > > Hi Jason, > > >> > > > > > > > > > > > > >> > > > > > > > > > > I think there may be some problems with the > > >> > > > > > > > > > > direction we are discussing. > > >> > > > > > > > > > Probably not. > > >> > > > > > > > > > > > >> > > > > > > > > > As far as we are focusing on technology, there's > > >> > > > > > > > > > nothing wrong from my > > >> > > > > > > > > > perspective. And this is how the community works. Your > > >> > > > > > > > > > idea needs to > > >> > > > > > > > > > be justified and people are free to raise any > > >> > > > > > > > > > technical questions > > >> > > > > > > > > > especially considering you've posted a spec change > > >> > > > > > > > > > with prototype > > >> > > > > > > > > > codes but not only the idea. > > >> > > > > > > > > > > > >> > > > > > > > > > > Our > > >> > > > > > > > > > > goal is to add an new ism device. As far as the spec > > >> > > > > > > > > > > is concerned, we are not > > >> > > > > > > > > > > concerned with the implementation of the backend. > > >> > > > > > > > > > > > > >> > > > > > > > > > > The direction we should discuss is what is the > > >> > > > > > > > > > > difference between the ism device > > >> > > > > > > > > > > and other devices such as virtio-net, and whether it > > >> > > > > > > > > > > is necessary to introduce > > >> > > > > > > > > > > this new device. > > >> > > > > > > > > > This is somehow what I want to ask, actually it's not > > >> > > > > > > > > > a comparison > > >> > > > > > > > > > with virtio-net but: > > >> > > > > > > > > > > > >> > > > > > > > > > - virtio-roce > > >> > > > > > > > > > - virtio-vhost-user > > >> > > > > > > > > > - virtio-(p)mem > > >> > > > > > > > > > > > >> > > > > > > > > > or whether we can simply add features to those devices > > >> > > > > > > > > > to achieve what > > >> > > > > > > > > > you want to do here. > > >> > > > > > > > > > > >> > > > > > > > > Yes, this is my priority to discuss. > > >> > > > > > > > > > > >> > > > > > > > > At the moment, I think the most similar to ism is the > > >> > > > > > > > > Vhost-user Device Backend > > >> > > > > > > > > of virtio-vhost-user. > > >> > > > > > > > > > > >> > > > > > > > > My understanding of it is to map any virtio device to > > >> > > > > > > > > another vm as a vvu > > >> > > > > > > > > device. > > >> > > > > > > > Yes, so a possible way is to have a device with memory > > >> > > > > > > > zone/region > > >> > > > > > > > provision and management then map it via virtio-vhost-user. > > >> > > > > > > > > >> > > > > > > Yes, there is such a possibility. virtio-vhost-user makes me > > >> > > > > > > feel that what can > > >> > > > > > > be shared is the function implementation of map. > > >> > > > > > > > > >> > > > > > > But in the vm to provide the interface to the upper layer, I > > >> > > > > > > think this is the > > >> > > > > > > work of ism. > > >> > > > > > > > > >> > > > > > > But one of the reasons why I didn't use virtio-vhost-user > > >> > > > > > > directly is that in > > >> > > > > > > another vm, the guest can operate the vvu device, which we > > >> > > > > > > hope that both sides > > >> > > > > > > are equal to the ism device. > > >> > > > > > > > > >> > > > > > > So I want to agree on a question first: who will provide the > > >> > > > > > > upper layer with > > >> > > > > > > the ability to share the memory area? > > >> > > > > > > > > >> > > > > > > Our answer is a new ism device. How does this device achieve > > >> > > > > > > memory sharing, I > > >> > > > > > > think is the second question. > > >> > > > > > > > > >> > > > > > > > > >> > > > > > > > > From this design purpose, I think the two are different. > > >> > > > > > > > > > > >> > > > > > > > > Of course, you might want to extend it, it does have > > >> > > > > > > > > some similarities and uses > > >> > > > > > > > > a lot of similar techniques. > > >> > > > > > > > I don't have any preference so far. If you think your idea > > >> > > > > > > > makes more > > >> > > > > > > > sense, then try your best to justify it in the list. > > >> > > > > > > > > > >> > > > > > > > > So we can really discuss in this direction, whether > > >> > > > > > > > > the vvu device can be extended to achieve the purpose of > > >> > > > > > > > > ism, or whether the > > >> > > > > > > > > design goals can be agreed. > > >> > > > > > > > I've added Stefan in the loop, let's hear from him. > > >> > > > > > > > > > >> > > > > > > > > Or, in the direction of memory sharing in the backend, > > >> > > > > > > > > can ism and vvu be merged? > > >> > > > > > > > > Should device/driver APIs remain independent? > > >> > > > > > > > Btw, you mentioned that one possible user of ism is the > > >> > > > > > > > smc, but I > > >> > > > > > > > don't see how it connects to that with your prototype > > >> > > > > > > > driver. > > >> > > > > > > Yes, we originally had plans, but the virtio spec was > > >> > > > > > > considered for submission, > > >> > > > > > > so this was not included. Maybe, we should have included > > >> > > > > > > this part @Tony > > >> > > > > > > > > >> > > > > > > A brief introduction is that SMC currently has a > > >> > > > > > > corresponding > > >> > > > > > > s390/net/ism_drv.c and we will replace this in the > > >> > > > > > > virtualization scenario. > > >> > > > > > > >> > > > > > > >> > > > > Ok, I see. So I think the goal is to implement something in > > >> > > > > virtio that is > > >> > > > > functional equivalent to IBM ISM device. > > >> > > > > > > >> > > > > > >> > > > Yes, IBM ISM devices do something similar and it inspired this. > > >> > > > > >> > > Ok, it would be better to mention this in the cover letter of the > > >> > > next > > >> > > version. This can ease the reviewers (IBM has some good docs of those > > >> > > from the website). > > >> > > > > >> > > > >> > Yes, we will do it. > > >> > > >> Btw, I wonder about the plan to support live migration. E.g do we need > > >> to hot unplug the ism device before the migration then we can fallback > > >> to TCP/IP ? > > >> > > > > > >>From the point view of SMC, SMC-R maintains multiple link (RDMA QP), it > > >can live migrate existed connections to new link. > > > > > >Currently, yes, for SMC-D. > > > > I think Jason means VM live migration from one Host to another. Am I > > right, Jason ?
Yes. > > > > In that case, the share memory from the ISM device is no longer valid, > > I think we have to hot unplug before the migration to notify SMC that > > the SMC-D link is no longer usable. > > Yes, this is what I mean ;-) SMC-D needs to unplug the device. > > > IIUC, SMC-D doesn't support transparently fallback to TCP/IP in this case > > now. But I think we could make that happen, since SMC already support link > > migration between different RDMA devices. > > Yes, currently SMC-D doesn't support migration to another device or > fallback. And SMC-R supports migration to another link, no fallback. Ok. I see. Thanks > > Cheers, > Tony Lu > > > Thanks > > > > > > > >Cheers, > > >Tony Lu > > > > > > > > >> Thanks > > >> > > >> > > > >> > > > > > >> > > > > > > >> > > > > > > > > >> > > > > > > Thanks. > > >> > > > > > > > > >> > > > > > SMC is a network protocol which is modeled by shared memory > > >> > > > > > rather than > > >> > > > > > packet. > > >> > > > > > > >> > > > > > > >> > > > > After reading more SMC from IBM website, I think you meant SMC-D > > >> > > > > here. And I > > >> > > > > wonder in order to have a complete SMC solution we still need > > >> > > > > virtio-ROCE > > >> > > > > for inter host communcation? > > >> > > > > > > >> > > > > > >> > > > Mostly yes. > > >> > > > > > >> > > > SMC-D is the part of whole SMC solution. SMC supports multiple > > >> > > > underlying device, -D means ISM device, -R means RDMA device. The > > >> > > > key > > >> > > > data model is shared memory, SMC uses RDMA (-R) or ISM(-D) to > > >> > > > *share* > > >> > > > memory between peers, and it will choose the suitable device on > > >> > > > demand > > >> > > > during handshaking. If there was no suitable device, it would fall > > >> > > > back > > >> > > > to TCP. So virtio-ROCE is not required. > > >> > > > > >> > > So the commniting peers on the same host we need SMC-D, in the future > > >> > > we need to use RDMA to offload the communication among the peers of > > >> > > different hosts. Then we can get fully transparent offload no matter > > >> > > the peer is local or not. > > >> > > > > >> > > > >> > Yes, this is what we want to do. > > >> > > > >> > > > > > >> > > > > > > >> > > > > > Actually the basic required interfaces of SMC device are: > > >> > > > > > > > >> > > > > > - alloc / free memory region, each connection peer has two > > >> > > > > > memory > > >> > > > > > regions dynamically for sending and receiving ring buffer. > > >> > > > > > - attach / detach memory region, remote attaches > > >> > > > > > local-allocated > > >> > > > > > sending region as receiving region, vice versa. > > >> > > > > > - notify, tell peer to read data and update cursor. > > >> > > > > > > > >> > > > > > Then the device can be registered as SMC ISM device. Of > > >> > > > > > course, SMC > > >> > > > > > also requires some modification to adapt it. > > >> > > > > > > >> > > > > > > >> > > > > Looking at s390 ism driver it requires other stuffs like vlan > > >> > > > > add/remove or > > >> > > > > gid query, do we need them as well? > > >> > > > > > >> > > > vlan is not required in this use case. ISM uses gid to identified > > >> > > > each > > >> > > > others, maybe we could implement it in virtio ways. > > >> > > > > >> > > I'd suggest adding the codes to register the driver to SMC/ISM in the > > >> > > next version (instead of a simple procfs hooking). Then people can > > >> > > easily play or review. > > >> > > > > >> > > > >> > Ok, I will add the codes in the next version. > > >> > > > >> > Cheers, > > >> > Tony Lu > > >> > > > >> > > Thanks > > >> > > > > >> > > > > > >> > > > To support virtio-ism smoothly, the interfaces of ISM driver still > > >> > > > need > > >> > > > to be adjusted. I will put it on the table with IBM people. > > >> > > > > > >> > > > Cheers, > > >> > > > Tony Lu > > >> > > > > > >> > > > > > > >> > > > > Thanks > > >> > > > > > > >> > > > > > > >> > > > > > > > >> > > > > > Cheers, > > >> > > > > > Tony Lu > > >> > > > > > > > >> > > > > > > > Thanks > > >> > > > > > > > > > >> > > > > > > > > Thanks. > > >> > > > > > > > > > > >> > > > > > > > > > > >> > > > > > > > > > > How to share the backend with other deivce is > > >> > > > > > > > > > > another problem. > > >> > > > > > > > > > Yes, anything that is used for your virito-ism > > >> > > > > > > > > > prototype can be used > > >> > > > > > > > > > for other devices. > > >> > > > > > > > > > > > >> > > > > > > > > > > Our goal is to dynamically obtain a piece of memory > > >> > > > > > > > > > > to share with other vms. > > >> > > > > > > > > > So at this level, I don't see the exact difference > > >> > > > > > > > > > compared to > > >> > > > > > > > > > virtio-vhost-user. Let's just focus on the API that > > >> > > > > > > > > > carries on the > > >> > > > > > > > > > semantic: > > >> > > > > > > > > > > > >> > > > > > > > > > - map/unmap > > >> > > > > > > > > > - permission update > > >> > > > > > > > > > > > >> > > > > > > > > > The only missing piece is the per region notification. > > >> > > > > > > > > > > > >> > > > > > > > > > > In a connection, this memory will be used > > >> > > > > > > > > > > repeatedly. As far as SMC is concerned, > > >> > > > > > > > > > > it will use it as a ring. Of course, we also need a > > >> > > > > > > > > > > notify mechanism. > > >> > > > > > > > > > > > > >> > > > > > > > > > > That's what we're aiming for, so we should first > > >> > > > > > > > > > > discuss whether this > > >> > > > > > > > > > > requirement is reasonable. > > >> > > > > > > > > > So unless somebody said "no", it is fine until now. > > >> > > > > > > > > > > > >> > > > > > > > > > > I think it's a feature currently not supported by > > >> > > > > > > > > > > other devices specified by the current virtio spce. > > >> > > > > > > > > > Probably, but we've already had rfcs for roce and > > >> > > > > > > > > > vhost-user. > > >> > > > > > > > > > > > >> > > > > > > > > > Thanks > > >> > > > > > > > > > > > >> > > > > > > > > > > Thanks. > > >> > > > > > > > > > > > > >> > > > > > > > > > > > > >> > > > > > >> > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: [email protected] > For additional commands, e-mail: [email protected] > --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
