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Tue, 28 Jan 2020 16:47:19 +0000 (UTC) Date: Tue, 28 Jan 2020 16:47:17 +0000 From: "Dr. David Alan Gilbert" To: John Snow Subject: Re: [PATCH v3 00/13] RFC: [for 5.0]: HMP monitor handlers cleanups Message-ID: <20200128164717.GT3215@work-vm> References: <20200127103647.17761-1-mlevitsk@redhat.com> <2e885a1d-94c7-53b5-44f7-feffe70f57c3@redhat.com> <20200127204355.GE4544@andariel.pipo.sk> <12217cd6-7866-ce9c-c0da-24775f9d045d@redhat.com> MIME-Version: 1.0 In-Reply-To: <12217cd6-7866-ce9c-c0da-24775f9d045d@redhat.com> User-Agent: Mutt/1.13.3 (2020-01-12) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-MC-Unique: SGZ_omfANWeFFAs7T0bV3w-1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 207.211.31.120 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kevin Wolf , Peter Krempa , Jan Tomko , qemu-block@nongnu.org, Markus Armbruster , qemu-devel@nongnu.org, Max Reitz , Gerd Hoffmann , Maxim Levitsky Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * John Snow (jsnow@redhat.com) wrote: >=20 >=20 > On 1/27/20 3:43 PM, Peter Krempa wrote: > > On Mon, Jan 27, 2020 at 14:39:02 -0500, John Snow wrote: > >> > >> > >> On 1/27/20 5:36 AM, Maxim Levitsky wrote: > >>> This patch series is bunch of cleanups > >>> to the hmp monitor code. > >>> > >>> This series only touched blockdev related hmp handlers. > >>> > >>> No functional changes expected other that > >>> light error message changes by the last patch. > >>> > >>> This was inspired by this bugzilla: > >>> https://bugzilla.redhat.com/show_bug.cgi?id=3D1719169 > >>> > >>> Basically some users still parse hmp error messages, > >>> and they would like to have them prefixed with 'Error:' > >>> > >> > >> HMP isn't meant to be parsed. It's explicitly *not* API or ABI. I do > >> like consistency in my UIs (it's useful for human eyes, too), but I'd > >> like to know more about the request. > >=20 > > That's true as long as there's an stable replacement ... see below. > >=20 >=20 > Thanks for the context! >=20 > >> > >> Is this request coming from libvirt? Can we wean them off of this > >> interface? What do they need as a replacement? > >=20 > > There are 5 commands that libvirt still has HMP interfaces for: > >=20 > > drive_add > > drive_del > >=20 > > savevm > > loadvm > > delvm > >=20 > > From upstream point of view there's no value in adding the 'error' > > prefix to drive_add/drive_del as libvirt now uses blockdev-add/del QMP > > command instead which have implicit error propagation. > >=20 >=20 > As thought. >=20 > > There are no replacements for the internal snapshot commands, but they > > reported the 'error' prefix for some time even before this series. > >=20 > > Said that, please don't break savevm/loadvm/delvm until a QMP > > replacement is added. > >=20 >=20 > Yes, noted. I wonder where userfaultfd write support is these days... How would that help you there? Dave > > The bug was reported at the time when libvirt didn't use blockdev yet, > > but at this point it's pointless from our side. This wouldn't even fix > > the scenario when old (pre-5.10) libvirt would use new qemu because the > > drive-add handler never checked the error prefix. > >=20 > > [1] https://libvirt.org/git/?p=3Dlibvirt.git;a=3Dblob;f=3Dsrc/qemu/qemu= _monitor_text.c;h=3D9135a11f0a3aae718c86bb199112fba8d16d4d80;hb=3DHEAD > >=20 >=20 > Thank you for the report from libvirtville :) >=20 > --js -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK