From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50018) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ePWum-0004yp-Lr for qemu-devel@nongnu.org; Thu, 14 Dec 2017 12:03:21 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ePWui-0000HW-KJ for qemu-devel@nongnu.org; Thu, 14 Dec 2017 12:03:20 -0500 Received: from mx1.redhat.com ([209.132.183.28]:33100) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1ePWui-0000H0-CC for qemu-devel@nongnu.org; Thu, 14 Dec 2017 12:03:16 -0500 References: <20171023151310.6462-1-vadim.galitsyn@profitbricks.com> From: Eric Blake Message-ID: Date: Thu, 14 Dec 2017 11:03:12 -0600 MIME-Version: 1.0 In-Reply-To: <20171023151310.6462-1-vadim.galitsyn@profitbricks.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="p39bTnfK34bpD0m7MI1MkWshAd09jfR3h" Subject: Re: [Qemu-devel] QMP, HMP: introduce 'writeconfig' command List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Vadim Galitsyn , Markus Armbruster , "Dr . David Alan Gilbert" , qemu-devel@nongnu.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --p39bTnfK34bpD0m7MI1MkWshAd09jfR3h From: Eric Blake To: Vadim Galitsyn , Markus Armbruster , "Dr . David Alan Gilbert" , qemu-devel@nongnu.org Message-ID: Subject: Re: QMP, HMP: introduce 'writeconfig' command References: <20171023151310.6462-1-vadim.galitsyn@profitbricks.com> In-Reply-To: <20171023151310.6462-1-vadim.galitsyn@profitbricks.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On 10/23/2017 10:13 AM, Vadim Galitsyn 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 think we should expose 'writeconfig' via QMP as long as there is still the chance of inconsistent data being written. And I think we have a lot more issues where existing code abuses QemuOpts in ways that current configuration does not match the original command line, but where you cannot easily expose the current configuration in a way that would be reparsed by the command line into the current state. Therefore, I'm not sure this series is worthwhile. --=20 Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org --p39bTnfK34bpD0m7MI1MkWshAd09jfR3h Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Comment: Public key at http://people.redhat.com/eblake/eblake.gpg Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEzBAEBCAAdFiEEccLMIrHEYCkn0vOqp6FrSiUnQ2oFAloyrtEACgkQp6FrSiUn Q2oHNgf/Txofw1kLP5Okt9O6j3YiV3g1fzRXskAa8ig1lw7OvnKtqL6C420MhsN8 wcVH0cnAjs8qtaiu/O6vi6dN2pZUazS8jcmFYAhkk8qH1sxAfHYoNfA6THQ9pC0P t0CVN48uXaZBVrqKrcbgxhrRowx2SMDsjc3vlZytSBnqUoakdxZ0S27lYGLBrAPS 4m492UWEbz02cRAY3WeqcGrFasnzWggn3/unvuM4B5Vd0CyE2KjoevJNee9xDDLL lt+dVLlRFvVMHaQ8EZJ5WI+J3oJQywKuyXraQ6hnCUgiW5q74iWfMp/UFAT5GPd5 TMXiz8NzAlRTOXj7xb3xuBqNx9lP7A== =m7NC -----END PGP SIGNATURE----- --p39bTnfK34bpD0m7MI1MkWshAd09jfR3h--