Re: RFC: New device for zero-copy VM memory access

[geoff@hostfission.com]

On 2019-11-01 02:52, Dr. David Alan Gilbert wrote:
> * geoff@hostfission.com (geoff@hostfission.com) wrote:
>> 
>> 
>> On 2019-11-01 01:52, Peter Maydell wrote:
>> > On Thu, 31 Oct 2019 at 14:26, <geoff@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

> 
> Dave
> 
>> >
>> > thanks
>> > -- PMM
> --
> Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK