From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49471) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1blxFY-0007Op-SU for qemu-devel@nongnu.org; Mon, 19 Sep 2016 08:00:46 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1blxFT-00089X-N6 for qemu-devel@nongnu.org; Mon, 19 Sep 2016 08:00:39 -0400 Received: from mx1.redhat.com ([209.132.183.28]:44762) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1blxFT-00089F-Ad for qemu-devel@nongnu.org; Mon, 19 Sep 2016 08:00:35 -0400 Date: Mon, 19 Sep 2016 13:00:29 +0100 From: "Dr. David Alan Gilbert" Message-ID: <20160919120029.GB2041@work-vm> References: <1473157086-12062-1-git-send-email-dgilbert@redhat.com> <87h99kdwha.fsf@dusky.pond.sub.org> <20160914103005.GA2852@work-vm> <20160914104831.GH28399@redhat.com> <87d1k0l036.fsf@dusky.pond.sub.org> <20160919095449.GJ15201@redhat.com> <20160919115424.GM15201@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20160919115424.GM15201@redhat.com> Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH v2] qom: Implement qom-get HMP command List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Daniel P. Berrange" Cc: Markus Armbruster , kwolf@redhat.com, qemu-devel@nongnu.org, lcapitulino@redhat.com, arei.gonglei@huawei.com, pbonzini@redhat.com, afaerber@suse.de * Daniel P. Berrange (berrange@redhat.com) wrote: > On Mon, Sep 19, 2016 at 10:54:49AM +0100, Daniel P. Berrange wrote: > > On Mon, Sep 19, 2016 at 11:18:05AM +0200, Markus Armbruster wrote: > > > "Daniel P. Berrange" writes: > > >=20 > > > > On Wed, Sep 14, 2016 at 11:30:06AM +0100, Dr. David Alan Gilbert = wrote: > > > >> * Markus Armbruster (armbru@redhat.com) wrote: > > > >> > "Dr. David Alan Gilbert (git)" writes: > > > >> >=20 > > > >> > > From: "Dr. David Alan Gilbert" > > > >> > > > > > >> > > This started off as Andreas F=E4rber's implementation from > > > >> > > March 2015, but after feedback from Paolo morphed into > > > >> > > using the json output which handles structs reasonably. > > > >> > > > > > >> > > Use with qom-list to find the members of an object. > > > >> > > > > > >> > > (qemu) qom-get /backend/console[0]/device/vga.rom[0] size > > > >> > > 65536 > > > >> > > (qemu) qom-get /machine smm > > > >> > > "auto" > > > >> > > (qemu) qom-get /machine rtc-time > > > >> > > { > > > >> > > "tm_year": 116, > > > >> > > "tm_sec": 0, > > > >> > > "tm_hour": 9, > > > >> > > "tm_min": 46, > > > >> > > "tm_mon": 8, > > > >> > > "tm_mday": 6 > > > >> > > } > > > >> > > (qemu) qom-get /machine frob > > > >> > > Property '.frob' not found > > > >> > > > > > >> > > Signed-off-by: Dr. David Alan Gilbert > > > >> >=20 > > > >> > Ignorant question: how does qom-set deal with structs? > > > >> >=20 > > > >> > I tried the obvious > > > >> >=20 > > > >> > (qemu) qom-set /machine rtc-time abc > > > >> > Insufficient permission to perform this operation > > > >>=20 > > > >> I don't think it does. > > > > > > > > Indeed it can't - qom_set ends up calling object_property_parse w= hich > > > > uses string-input-visitor to parse the value, which can only hand= le > > > > scalars as the magic special case list-of-ints. > > > > > > > > To deal with compound properties would really require us to use a > > > > qdict_crumple + qmp_input_visitor combination, similar to how I'v= e > > > > made -object and object_add be able to deal with compound propert= ies. > > >=20 > > > HMP I/O formats are not ABI. We can use visitors in whatever way w= e > > > want, as long as we keep -get and -set consistent. The sane way to= do > > > that is using the same kind of visitor for both, in its input and o= utput > > > form, respectively. > > >=20 > > > Right now, qom-set uses the string input visitor. As long as it do= es > > > that, qom-get should use the string output visitor. Sadly, this pa= ir of > > > visitors is quite limited ("does not implement support for visiting= QAPI > > > structs, alternates, null, or arbitrary QTypes"). We can extend it= to > > > cover more, or we can switch to another, less limited pair of visit= ors. > > >=20 > > > Can we agree on what to do so we can have qom-get sooner rather tha= n > > > later? It doesn't have to be perfect, we can iterate. > >=20 > > I think that -object sets the precedent that the rest should ultimate= ly > > follow. It currently uses the opts visitor syntax, but is being switc= hed > > over to the combination of qdict_crumple + qobject input visitor, whi= ch > > is basically the same as opts visitor syntax for scalars and with dot= ted > > notation for compound types. > >=20 > > The HMP object_add command will use the exact same syntax as -object > > CLI arg. Given this, I think 'qom-set' really ought to be updated to = use > > qdict_crumple + qobject input visitor too, so it can deal with compou= nd > > types. In fact I'd view the lack of conversion of qom-set as a mistak= e > > in my patch series - I should have converted that too, while adding > > support for compound properties to -object and object_add. > >=20 > > This ultimately means that qom-get probably ought to use qobject outp= ut > > visitor, followed by a qdict flatten operation to turn the nested > > dicts/lists, into a flat dict with dotted syntax. >=20 > Further, QOM has two methods which are intended to be mirror imges > of each other - object_property_parse and object_property_print. > The current qom-set impl uses object_property_parse, so we ought > to make 'qom-get' use object_property_print. >=20 > We would still need to enhance object_property_print() to deal with > compound types, but that's doesn't have to be a blocker - Dave's > qom-get patch can just use object_property_print() as it exists today > and we can enhance the impl separately. That's what the v1 version of Andreas/my patch did isn't it? Dave > Regards, > Daniel > --=20 > |: http://berrange.com -o- http://www.flickr.com/photos/dberran= ge/ :| > |: http://libvirt.org -o- http://virt-manager.= org :| > |: http://autobuild.org -o- http://search.cpan.org/~danbe= rr/ :| > |: http://entangle-photo.org -o- http://live.gnome.org/gtk-= vnc :| -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK