From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:38580) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1blyLl-0001oC-7H for qemu-devel@nongnu.org; Mon, 19 Sep 2016 09:11:13 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1blyLf-00083y-FI for qemu-devel@nongnu.org; Mon, 19 Sep 2016 09:11:08 -0400 Received: from mx1.redhat.com ([209.132.183.28]:56430) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1blyLf-00083s-5X for qemu-devel@nongnu.org; Mon, 19 Sep 2016 09:11:03 -0400 From: Markus Armbruster 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> <20160919120029.GB2041@work-vm> Date: Mon, 19 Sep 2016 15:11:00 +0200 In-Reply-To: <20160919120029.GB2041@work-vm> (David Alan Gilbert's message of "Mon, 19 Sep 2016 13:00:29 +0100") Message-ID: <87y42of317.fsf@dusky.pond.sub.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 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: "Dr. David Alan Gilbert" Cc: "Daniel P. Berrange" , kwolf@redhat.com, qemu-devel@nongnu.org, lcapitulino@redhat.com, arei.gonglei@huawei.com, pbonzini@redhat.com, afaerber@suse.de "Dr. David Alan Gilbert" writes: > * 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 w= rote: >> > > >> * Markus Armbruster (armbru@redhat.com) wrote: >> > > >> > "Dr. David Alan Gilbert (git)" writes: >> > > >> >=20 >> > > >> > > From: "Dr. David Alan Gilbert" >> > > >> > > >> > > >> > > This started off as Andreas F=C3=A4rber'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 wh= ich >> > > > uses string-input-visitor to parse the value, which can only handle >> > > > 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've >> > > > made -object and object_add be able to deal with compound properti= es. >> > >=20 >> > > HMP I/O formats are not ABI. We can use visitors in whatever way we >> > > 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 ou= tput >> > > form, respectively. >> > >=20 >> > > Right now, qom-set uses the string input visitor. As long as it does >> > > that, qom-get should use the string output visitor. Sadly, this pai= r 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 visito= rs. >> > >=20 >> > > Can we agree on what to do so we can have qom-get sooner rather than >> > > later? It doesn't have to be perfect, we can iterate. >> >=20 >> > I think that -object sets the precedent that the rest should ultimately >> > follow. It currently uses the opts visitor syntax, but is being switch= ed >> > over to the combination of qdict_crumple + qobject input visitor, which >> > is basically the same as opts visitor syntax for scalars and with dott= ed >> > 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 u= se >> > qdict_crumple + qobject input visitor too, so it can deal with compound >> > types. In fact I'd view the lack of conversion of qom-set as a mistake >> > 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 output >> > 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? Looks like it :)