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Re: [Xen-devel] use xs_watch from userspace and use epoll instead of sel

To: Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel] use xs_watch from userspace and use epoll instead of select
From: Vasiliy G Tolstov <v.tolstov@xxxxxxxxx>
Date: Mon, 06 Jun 2011 14:05:12 +0400
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On Mon, 2011-06-06 at 10:48 +0100, Ian Campbell wrote:
> On Mon, 2011-06-06 at 09:58 +0100, Vasiliy G Tolstov wrote:
> > Code to using from domU. I'm correct all my mistakes and now relative
> > and full path watches work's fine with epoll and select based looping.
> > Sorry for wrong panic about it. 
> Oh good.
> > Sorry for small offtop, where i can find example to use grand pages to
> > transfer for example 1byte from domU to dom) and vice versa?
> (it's "grant" pages).
> Any of the PV drivers would give a decent example for in kernel use of
> grant tables to setup a shared memory buffer, but I guess you are asking
> for a userspace example? The principals are mostly the same, except you
> use xc_* functions instead of the kernel ones.
> qemu contains some userspace backends, for example the xenfb backend.
> Daniel de Graaf posted some patches to make this use grant tables back
> in February/March this year -- you should check the ML archives. There
> are also PV disk and net backends in qemu.
> I can't think of any userspace frontends offhand.
> Once you have a shared page you can use the standard Xen ring.h
> datastructures to define your request and response protocol.
> What are you actually trying to build?
> Ian.

I'm try to build daemon, that can recieve command via xenstore (xs_watch
for specific path), via /dev/hvcN (serial char interface), now i'm try
to use gntmem mechanism to do this too. If one method not available or
not work or some errors accured - i'm try next. 
/dev/hvcN Not good sometimes, becouse in some domU i have gentty on this
xenstore - has limit in size of message...
In kernel side xen thing more easy to understand. Use it under userspace
need deep googling =).
Ok if i use grant pages mechanism - do i have notify for new message
after it arrives? If i use xs from domU i need libxc under it insted of
libxenstore ?

Vasiliy G Tolstov <v.tolstov@xxxxxxxxx>

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