From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori Subject: Re: [Qemu-devel] KVM call minutes for Mar 15 Date: Tue, 15 Mar 2011 16:05:32 -0500 Message-ID: <4D7FD49C.7070108@codemonkey.ws> References: <20110315145346.GH20456@x200.localdomain> <4D7F93AB.4050207@codemonkey.ws> <20110315190606.GM20456@x200.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org, libvir-list@redhat.com, qemu-devel@nongnu.org, Chris Lalancette , Jiri Denemark To: Chris Wright Return-path: Received: from mail-iy0-f174.google.com ([209.85.210.174]:59118 "EHLO mail-iy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758696Ab1COVFn (ORCPT ); Tue, 15 Mar 2011 17:05:43 -0400 Received: by iyb26 with SMTP id 26so988456iyb.19 for ; Tue, 15 Mar 2011 14:05:42 -0700 (PDT) In-Reply-To: <20110315190606.GM20456@x200.localdomain> Sender: kvm-owner@vger.kernel.org List-ID: On 03/15/2011 02:06 PM, Chris Wright wrote: > * Anthony Liguori (anthony@codemonkey.ws) wrote: >> On 03/15/2011 09:53 AM, Chris Wright wrote: >>> QAPI > >>> - c library implementation is critical to have unit tests and test >>> driven development >>> - thread safe? >>> - no shared state, no statics. >>> - threading model requires lock for the qmp session >>> - licensiing? >>> - LGPL >>> - forwards/backwards compat? >>> - designed with that in mind see wiki: >>> >>> http://wiki.qemu.org/Features/QAPI >> One neat feature of libqmp is that once libvirt has a better QMP >> passthrough interface, we can create a QmpSession that uses libvirt. >> >> It would look something like: >> >> QmpSession *libqmp_session_new_libvirt(virDomainPtr dom); > Looks like you mean this? > > -> request QmpSession -> > client libvirt > <- return QmpSession<- > > client -> QmpSession -> QMP -> QEMU Maybe, your ASCII art confuses me :-) QmpSession is just a wrapper around a transport. It can be an fd that you read() and write() JSON strings to, but it's just as easy to read and write through JSON strings via virQemuMonitorCommand() or whatever the interface currently is. > So bypassing libvirt completely to actually use the session? > > Currently, it's more like: > > client -> QemuMonitorCommand -> libvirt -> QMP -> QEMU It's not bypassing. It's an API on top of a libvirt command. FWIW, the code generator could be trivially modified to generate a libvirt style API if there's any interest. So instead of: void qmp_block_passwd(QmpSession *sess, const char *device, const char *password, Error **errp); It would be: int virQemuBlockPasswd(virDomainPtr dom, const char *device, const char *password); But I'm not sure that's really that useful. >> The QmpSession returned by this call can then be used with all of >> the libqmp interfaces. This means we can still exercise our test >> suite with a guest launched through libvirt. It also should make >> the libvirt pass through interface a bit easier to consume by third >> parties. > This sounds like it's something libvirt folks should be involved with. > At the very least, this mode is there now and considered basically > unstable/experimental/developer use: > > "Qemu monitor command '%s' executed; libvirt results may be unpredictable!" > > So likely some concern about making it easier to use, esp. assuming > that third parties above are mgmt apps, not just developers. To be clear, there's no real support needed from libvirt here other than the passthrough. How that interface is supported in libvirt is more or less orthogonal to libqmp. libqmp is a C API to QMP. It can speak QMP over whatever transports speak QMP. If you can speak QMP to libvirt, then it's only natural to bridge libqmp to libvirt. Regards, Anthony Liguori > thanks, > -chris >