* ge...@hostfission.com (ge...@hostfission.com) wrote: > > > On 2019-11-03 21:10, ge...@hostfission.com wrote: > > On 2019-11-01 02:52, Dr. David Alan Gilbert wrote: > > > * ge...@hostfission.com (ge...@hostfission.com) wrote: > > > > > > > > > > > > On 2019-11-01 01:52, Peter Maydell wrote: > > > > > On Thu, 31 Oct 2019 at 14:26, <ge...@hostfission.com> wrote: > > > > > > As the author of Looking Glass, I also have to consider the > > > > > > maintenance > > > > > > and the complexity of implementing the vhost protocol into the > > > > > > project. > > > > > > At this time a complete Porthole client can be implemented in 150 > > > > > > lines > > > > > > of C without external dependencies, and most of that is boilerplate > > > > > > socket code. This IMO is a major factor in deciding to avoid > > > > > > vhost-user. > > > > > > > > > > This is essentially a proposal that we should make our project and > > > > > code more complicated so that your project and code can be simpler. > > > > > I hope you can see why this isn't necessarily an argument that will > > > > > hold > > > > > very much weight for us :-) > > > > > > > > Certainly, I do which is why I am still going to see about using > > > > vhost, > > > > however, a device that uses vhost is likely more complex then > > > > the device > > > > as it stands right now and as such more maintenance would be > > > > involved on > > > > your end also. Or have I missed something in that vhost-user can > > > > be used > > > > directly as a device? > > > > > > The basic vhost-user stuff isn't actually that hard; if you aren't > > > actually shuffling commands over the queues you should find it pretty > > > simple - so I think your assumption about it being simpler if you > > > avoid > > > it might be wrong. It might be easier if you use it! > > > > I have been looking into this and I am yet to find some decent > > documentation or a simple device example I can use to understand how to > > create such a device. Do you know of any reading or examples I can > > obtain > > on how to get an initial do nothing device up and running? > > > > -Geoff > > Scratch that, the design just solidified for me and I am now making > progress, however it seems that vhost-user can't do what we need here: > > 1) I dont see any way to recieve notification of socket disconnection, in > our use case the client app needs to be able to be (re)connected > dynamically. It might be possible to get this event by registering it on > the chardev manually but this seems like it would be a kludge.
My understanding was that someone added support for reconnection of vhost-user; I'm not sure of the detail - cc'ing in Maxime and Marc-Andre. > 2) I don't see any method of notifying the vhost-user client of the > removal of a shared memory mapping. Again, these may not be persistently > mapped in the guest as we have no control over the buffer allocation, and > as such, we need a method to notify the client that the mapping has become > invalid. > > 3) VHOST_USER_SET_MEM_TABLE is a one time request, again this breaks our > usage as we need to change this dynamically at runtime. I've seen (3) being sent multiple times (It's messy but it happens); so I think that fixes (2) as well for you. Dave > Unless there are viable solutions to these problems there is no way that > vhost-user can be used for this kind of a device. > > -Geoff > > > > > > > > > Dave > > > > > > > > > > > > > thanks > > > > > -- PMM > > > -- > > > Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK -- Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
