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Re: CVS commit: src/tests/net/icmp

On Mon, 19 Jul 2010 12:35:08 +0300, Antti Kantee <> 
> On Mon Jul 12 2010 at 19:05:03 +0200, Jean-Yves Migeon wrote:
>> >> My initial step would be to have a block backend driver running in
>> >> userland, so I can make it run as a standalone server. Purpose is to
>> >> help diagnosing errors in a more graceful manner. I lost tremendous
>> >> time
>> >> tracking a DoS issue between frontend and backend drivers for domain
>> >> migration, for one stupid reason: the backend caused a DoS to the
>> >> of the *dom0* kernel, without even being capable of breaking into
>> >> ddb...
>> > 
>> > Ok, now I'm confused again.  If you want to make it run in dom0
>> > userspace,
>> > what is your interest with the hypercall api?  Or is that just the
>> > initial step?  I thought you wanted multiple "dom0"s.
>> Initial step.
> Guess I forgot respond to this.  What I wanted to say was that apart
> from some Makefiles, I'm not sure how much your initial step and final
> goal have in common implementation-wise.

Let's set the context. Backend drivers serve two main functionalities:
1 - copy/map the block/char requests from domU space to backend driver
space; this rely on the Xen API (hypercalls, event channels, ring I/O).
2 - rework these requests so that they could be passed further to other
layers, either vfs or network stacks.

All your work makes big improvements regarding (2). I would like to see
what I could do about (1).

What does it have to do with my final goal: 1 and 2 are largely
independant; the backend concept is shared by other microkernels
architectures (not opensource in my case, though). If I manage to
"virtualize" (1) (~= run the current kernel code in a POSIX userland
environment) without pulling in too much code (or losing operation
semantic), adding fs or network support to the environment would be, I
expect, easier than porting a complete kernel to the hypervisor/microkernel
API in question.

Jean-Yves Migeon

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