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Re: [Xen-devel] Re: Interdomain comms

I would be happiest (is Eric Van Hensbergen out there?) if we could move 
to a model where the basic inter-domain communications is 9p, with all 
that implies. I can try to say more if there is interest. 

Right now, there are multiple types of comms for inter-domain, which all
work very differently (consider vbd and network). I am continually dealing
with chasing changes in how things work, which can get tough in a non-gcc
world. From my point of view, the differences between (e.g.) bsd and linux 
are very minor compares to linux and plan 9. The biggest effort for me in 
forward-ports is dealing with gcc-isms in the code, and multiplying that 
by the number of different devices, adding in the binary structures, turns 
this into a lot of work.

It would sure be nice if the option were there to have a set of devices 
which all had the ring-buffer structure of (e.g.) the vbd, with no page 
loaning etc., and which allowed fairly arbitrary data transfer (i.e. not 
the current limits of vbd, with assumed 512-byte blocks and assumed 
upper-limits of 4096 bytes etc.). 

Plan 9 has shown that in practice a simple open/read/write/close model 
works fine for any device, and that devices can present a file-system-like 
interface to the kernel (and hence programs) and it all works. A lot of 
the binary structure of the current interdomain comms and devices could be 
eliminated and replaced with a common, simple abstraction usable for all 
devices. You could get rid of all the different bits of code (block, net, 
etc.) and replace with one simple bit of code. 


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