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From: Anthony PERARD <anthony.perard@citrix.com>
To: Ian Jackson <ian.jackson@citrix.com>
Cc: xen-devel@lists.xenproject.org, Wei Liu <wei.liu2@citrix.com>
Subject: Re: [RFC 4/4] HACK libxl_exec: Check QEMU status via QMP instead of xenstore
Date: Tue, 27 Mar 2018 18:58:26 +0100	[thread overview]
Message-ID: <20180327175826.GG2208@perard> (raw)
In-Reply-To: <23226.22973.741253.350174@mariner.uk.xensource.com>

On Tue, Mar 27, 2018 at 03:48:29PM +0100, Ian Jackson wrote:
> Anthony PERARD writes ("Re: [Xen-devel] [RFC 4/4] HACK libxl_exec: Check QEMU status via QMP instead of xenstore"):
> > On Tue, Mar 27, 2018 at 02:43:22PM +0100, Ian Jackson wrote:
> > > Right, but doesn't one still have to poll on connect() ?
> > 
> > Yes, we need to poll on connect().
> > 
> > libvirt those it also to open the socket:
> > https://libvirt.org/git/?p=libvirt.git;a=blob;f=src/qemu/qemu_monitor.c;h=e169553b7e1781da307ddb0be23fed5540baf36c;hb=HEAD#l375
> 
> Urgh.  Maybe we could fix this in qemu, or do some kind of hack.
> 
> For example, maybe we could instruct qemu to open some file or other,
> which is actually a pipe.  If it would happen late enought (after the
> qmp socket is set up).

I think that can be done.

If we add something like:
'-chardev','pipe,id=inotify,path=/tmp/pipe',
'-mon','chardev=inotify,mode=control',

And we just needs to wait until qemu write the QMP greating into the
pipe. At this point, the socket we cared for exist.

That /tmp/pipe can actually be a fd, I did not test it, only read the
code:
'-add-fd','fd=fd,set=1',
'-chardev','pipe,id=inotify,path=/dev/fdset/1',

I just need to write some code in libxl now.

-- 
Anthony PERARD

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      reply	other threads:[~2018-03-27 17:59 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-03-26 18:33 [RFC 0/4] libxl: Enable save/restore/migration of a restricted QEMU Anthony PERARD
2018-03-26 18:33 ` [RFC 1/4] libxl: Learned to send FD through QMP to QEMU Anthony PERARD
2018-03-27 10:29   ` Ian Jackson
2018-03-27 10:58     ` George Dunlap
2018-03-27 11:49       ` Anthony PERARD
2018-04-16 16:11     ` Anthony PERARD
2018-03-26 18:33 ` [RFC 2/4] libxl: Have QEMU save its state to a file descriptor Anthony PERARD
2018-03-26 18:34 ` [RFC 3/4] libxl_qmp: Implement query-status command Anthony PERARD
2018-03-26 18:34 ` [RFC 4/4] HACK libxl_exec: Check QEMU status via QMP instead of xenstore Anthony PERARD
2018-03-27 10:36   ` Ian Jackson
2018-03-27 11:13     ` Anthony PERARD
2018-03-27 13:43       ` Ian Jackson
2018-03-27 14:20         ` Anthony PERARD
2018-03-27 14:48           ` Ian Jackson
2018-03-27 17:58             ` Anthony PERARD [this message]

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