From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:52019) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1e6wie-0002bB-Sh for qemu-devel@nongnu.org; Tue, 24 Oct 2017 06:46:01 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1e6wib-0000Na-PA for qemu-devel@nongnu.org; Tue, 24 Oct 2017 06:46:00 -0400 Received: from mx1.redhat.com ([209.132.183.28]:37946) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1e6wib-0000N8-G2 for qemu-devel@nongnu.org; Tue, 24 Oct 2017 06:45:57 -0400 Date: Tue, 24 Oct 2017 11:45:53 +0100 From: "Dr. David Alan Gilbert" Message-ID: <20171024104552.GC3780@work-vm> References: <20171023151310.6462-1-vadim.galitsyn@profitbricks.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20171023151310.6462-1-vadim.galitsyn@profitbricks.com> Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] QMP, HMP: introduce 'writeconfig' command List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Vadim Galitsyn Cc: Markus Armbruster , Eric Blake , qemu-devel@nongnu.org * Vadim Galitsyn (vadim.galitsyn@profitbricks.com) wrote: > Hi Guys, >=20 > This thread is a continuation of discussion started in > http://lists.nongnu.org/archive/html/qemu-devel/2017-02/msg03182.html. >=20 > This series introduces =E2=80=98writeconfig=E2=80=99 command support fo= r QMP and HMP monitors. This functionality might be useful for live migra= tion for cases when guest configuration was modified in runtime (for exam= ple as a result of hot- plug/unplug operations) and actual Qemu command l= ine no longer reflects setup exposed to guest. >=20 > Original series has =E2=80=98qemu_opts=E2=80=99 patch as well (http://l= ists.nongnu.org/archive/html/qemu-devel/2017-02/msg03183.html) because HM= P=E2=80=99s =E2=80=98object_add=E2=80=99 result was not reflected in =E2=80= =98writeconfig=E2=80=99 output. Later I found that QMP=E2=80=99s =E2=80=98= object-add=E2=80=99 has the same issue. Anyway, I don=E2=80=99t include =E2= =80=98qemu_opts=E2=80=99 patches here because Markus mentioned (here http= ://lists.nongnu.org/archive/html/qemu-devel/2017-02/msg03476.html) that t= his functionality is going to be reworked in some future and such patches= might collide with the rework process. >=20 > Markus, could you please post if you have an update on this topic? Curr= ent =E2=80=98master=E2=80=99 branch (9993c82dc2f5ce58b41d708b765e1a717ad4= 281d) still has the issue. >=20 > Also, Markus mentioned that once configuration was changed during live = migration -- it might be an issue because =E2=80=98writeconfig=E2=80=99 d= ata became outdated (and might be make sense to think about to embed this= data into migration stream itself). In the same time David said that thi= s is another problem which is unrelated to this patch series. What is you= r current opinion on this topic? Can we consider these patches to be incl= uded into =E2=80=98master=E2=80=99 taking into account that not all confi= guration is dumped by =E2=80=98writeconfig=E2=80=99 (=E2=80=98object_add=E2= =80=99 problem), but this can be fixed later? I don't see anything wrong with having a 'writeconfig' command - we already have the command line equivalent - that is assuming hotplug etc all cause the values written to be correct. The data becoming outdated doesn't sound like a big issue to me; it's the management layer that's doing any hotplugs, it can reissue another 'writeconfig' command. Dave >=20 > Best regards, > Vadim >=20 >=20 -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK