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Re: [Xen-devel] simple backend, frontend

To: Georgios Portokalidis <georgios.portokalidis@xxxxxxxxx>
Subject: Re: [Xen-devel] simple backend, frontend
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Thu, 18 Nov 2004 17:50:41 +0000
Cc: Keir Fraser <keir.fraser@xxxxxxxxxxxx>, Deepak Manohar <mjdeepak@xxxxxxxxx>, mark.williamson@xxxxxxxxxxxx, andrew.warfield@xxxxxxxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxxxx
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> I have actually written some code for xen & xend allowing you to
> request the creation of an event channel and share a memory page. It's
> still work in progress, but it works fine. No crashes, very simple
> communication scheme.

Yes, for some things, where xend does not need to keep state on the
channel (e.g., network address info, blkdev info) then having a way to
get xend to just be a dumb channel for your evtchn/shared-mem info is
undoubtedly a good idea.

> The only possible problem i believe is the
> ctrl_if_register_receiver(). I think you can only register a single
> receiver for each control message type per domain. So even with a
> generic shared channel mechanism you will be able to use it just from
> a single driver/module.

Use the subtype field, or create another field within your message, to
demux on. Then have a small proxy module that registers with
ctrl_if.c but then demuxes and forwards the message to the appropriate
driver based on the demux field. You could have drivers register with
the proxy module instead of ctrl_if.

 -- Keir

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