What is the status of QEMU's transition from HMP to the QMP interface? My current understanding is that QEMU provides new HMP commands for humans, but HMP is being phased out as an API. Management tools should rely only on QMP for new commands. That would mean new HMP commands are not guaranteed to produce backwards-compatible output because tools are not supposed to parse the output. On the libvirt side, new QEMU features should only be supported via the json monitor in the future (i.e. human monitor patches should not be sent/merged)? Existing HMP commands will still need the human monitor support in order to handle old QEMU versions gracefully, but I'm thinking about new commands only. Does everyone agree on this? I think this is an important discussion if we want our management interface to get better and more consistent in the future.

Am 15.12.2011 14:18, schrieb Jan Kiszka: > On 2011-12-15 14:02, Stefan Hajnoczi wrote: >> What is the status of QEMU's transition from HMP to the QMP interface? >> >> My current understanding is that QEMU provides new HMP commands for >> humans, but HMP is being phased out as an API. Management tools >> should rely only on QMP for new commands. That would mean new HMP >> commands are not guaranteed to produce backwards-compatible output >> because tools are not supposed to parse the output. >> >> On the libvirt side, new QEMU features should only be supported via >> the json monitor in the future (i.e. human monitor patches should not >> be sent/merged)? Existing HMP commands will still need the human >> monitor support in order to handle old QEMU versions gracefully, but >> I'm thinking about new commands only. >> >> Does everyone agree on this? I think this is an important discussion >> if we want our management interface to get better and more consistent >> in the future. > > To phase out the classic HMP implementation, we need an internal > HMP-over-JSON wrapper (with tab expansion etc.) so that virtual console > and gdbstub monitors continue to benefit from new commands. Those > interfaces will stay for a long time, I'm sure. I think we're not talking about dropping HMP here, only about how long to support it as a stable API for management tools. I believe that we have been in a transitional phase for long enough now that we can start changing the output format of HMP commands without considering it an API breakage.

On 12/15/2011 11:33 AM, Kevin Wolf wrote: > Am 15.12.2011 14:18, schrieb Jan Kiszka: >> On 2011-12-15 14:02, Stefan Hajnoczi wrote: >>> What is the status of QEMU's transition from HMP to the QMP interface? >>> >>> My current understanding is that QEMU provides new HMP commands for >>> humans, but HMP is being phased out as an API. Management tools >>> should rely only on QMP for new commands. That would mean new HMP >>> commands are not guaranteed to produce backwards-compatible output >>> because tools are not supposed to parse the output. >>> >>> On the libvirt side, new QEMU features should only be supported via >>> the json monitor in the future (i.e. human monitor patches should not >>> be sent/merged)? Existing HMP commands will still need the human >>> monitor support in order to handle old QEMU versions gracefully, but >>> I'm thinking about new commands only. >>> >>> Does everyone agree on this? I think this is an important discussion >>> if we want our management interface to get better and more consistent >>> in the future. >> >> To phase out the classic HMP implementation, we need an internal >> HMP-over-JSON wrapper (with tab expansion etc.) so that virtual console >> and gdbstub monitors continue to benefit from new commands. Those >> interfaces will stay for a long time, I'm sure. > > I think we're not talking about dropping HMP here, only about how long > to support it as a stable API for management tools. I believe that we > have been in a transitional phase for long enough now that we can start > changing the output format of HMP commands without considering it an API > breakage. Yes, I've got the same impression. But while we are at it, forgive my naiveness, but wouldn't be worthwhile to consider dropping the human monitor in the long run?

On 2011-12-15 14:38, Lucas Meneghel Rodrigues wrote: > On 12/15/2011 11:33 AM, Kevin Wolf wrote: >> Am 15.12.2011 14:18, schrieb Jan Kiszka: >>> On 2011-12-15 14:02, Stefan Hajnoczi wrote: >>>> What is the status of QEMU's transition from HMP to the QMP interface? >>>> >>>> My current understanding is that QEMU provides new HMP commands for >>>> humans, but HMP is being phased out as an API. Management tools >>>> should rely only on QMP for new commands. That would mean new HMP >>>> commands are not guaranteed to produce backwards-compatible output >>>> because tools are not supposed to parse the output. >>>> >>>> On the libvirt side, new QEMU features should only be supported via >>>> the json monitor in the future (i.e. human monitor patches should not >>>> be sent/merged)? Existing HMP commands will still need the human >>>> monitor support in order to handle old QEMU versions gracefully, but >>>> I'm thinking about new commands only. >>>> >>>> Does everyone agree on this? I think this is an important discussion >>>> if we want our management interface to get better and more consistent >>>> in the future. >>> >>> To phase out the classic HMP implementation, we need an internal >>> HMP-over-JSON wrapper (with tab expansion etc.) so that virtual console >>> and gdbstub monitors continue to benefit from new commands. Those >>> interfaces will stay for a long time, I'm sure. >> >> I think we're not talking about dropping HMP here, only about how long >> to support it as a stable API for management tools. I believe that we >> have been in a transitional phase for long enough now that we can start >> changing the output format of HMP commands without considering it an API >> breakage. > > Yes, I've got the same impression. But while we are at it, forgive my > naiveness, but wouldn't be worthwhile to consider dropping the human > monitor in the long run? Surely not the interface (for virtual console & gdbstub), but the internal implementation I hope.

On Thu, Dec 15, 2011 at 1:49 PM, Kevin Wolf <kwolf(a)redhat.com&gt; wrote: > Am 15.12.2011 14:39, schrieb Jan Kiszka: >> On 2011-12-15 14:38, Lucas Meneghel Rodrigues wrote: >>> On 12/15/2011 11:33 AM, Kevin Wolf wrote: >>>> Am 15.12.2011 14:18, schrieb Jan Kiszka: >>>>> On 2011-12-15 14:02, Stefan Hajnoczi wrote: >>>>>> What is the status of QEMU's transition from HMP to the QMP interface? >>>>>> >>>>>> My current understanding is that QEMU provides new HMP commands for >>>>>> humans, but HMP is being phased out as an API. Management tools >>>>>> should rely only on QMP for new commands. That would mean new HMP >>>>>> commands are not guaranteed to produce backwards-compatible output >>>>>> because tools are not supposed to parse the output. >>>>>> >>>>>> On the libvirt side, new QEMU features should only be supported via >>>>>> the json monitor in the future (i.e. human monitor patches should not >>>>>> be sent/merged)? Existing HMP commands will still need the human >>>>>> monitor support in order to handle old QEMU versions gracefully, but >>>>>> I'm thinking about new commands only. >>>>>> >>>>>> Does everyone agree on this? I think this is an important discussion >>>>>> if we want our management interface to get better and more consistent >>>>>> in the future. >>>>> >>>>> To phase out the classic HMP implementation, we need an internal >>>>> HMP-over-JSON wrapper (with tab expansion etc.) so that virtual console >>>>> and gdbstub monitors continue to benefit from new commands. Those >>>>> interfaces will stay for a long time, I'm sure. >>>> >>>> I think we're not talking about dropping HMP here, only about how long >>>> to support it as a stable API for management tools. I believe that we >>>> have been in a transitional phase for long enough now that we can start >>>> changing the output format of HMP commands without considering it an API >>>> breakage. >>> >>> Yes, I've got the same impression. But while we are at it, forgive my >>> naiveness, but wouldn't be worthwhile to consider dropping the human >>> monitor in the long run? >> >> Surely not the interface (for virtual console & gdbstub), but the >> internal implementation I hope. > > Isn't HMP implemented in terms of QMP these days? Yes and no, I don't mean writing text manipulation code on to of QMP command handlers the way we're doing now. It's a pain. I meant more along the lines of making qmp-shell more human-friendly. You already can specify the command in a command-line fashion - you don't need to write raw JSON. I think it's a question of improving this and perhaps integrating the documentation for the QMP/QAPI commands right at the prompt so that it's easy to learn about the available commands. This would be a new interactive shell that stays much closer to QMP so that we don't bother with maintaining per-command text formatting functions like we do with HMP today.

What is the status of QEMU's transition from HMP to the QMP interface? My current understanding is that QEMU provides new HMP commands for humans, but HMP is being phased out as an API. Management tools should rely only on QMP for new commands. That would mean new HMP commands are not guaranteed to produce backwards-compatible output because tools are not supposed to parse the output. On the libvirt side, new QEMU features should only be supported via the json monitor in the future (i.e. human monitor patches should not be sent/merged)? Existing HMP commands will still need the human monitor support in order to handle old QEMU versions gracefully, but I'm thinking about new commands only. Does everyone agree on this? I think this is an important discussion if we want our management interface to get better and more consistent in the future.

On Thu, 15 Dec 2011 13:02:40 +0000 Stefan Hajnoczi&lt;stefanha(a)gmail.com&gt; wrote: > What is the status of QEMU's transition from HMP to the QMP interface? Depends on what you consider the transition to be. For management tools the transition can be considered done already because we do not support HMP as a stable interface. > My current understanding is that QEMU provides new HMP commands for > humans, but HMP is being phased out as an API. It already did. > Management tools > should rely only on QMP for new commands. That would mean new HMP > commands are not guaranteed to produce backwards-compatible output > because tools are not supposed to parse the output. Exactly. > On the libvirt side, new QEMU features should only be supported via > the json monitor in the future (i.e. human monitor patches should not > be sent/merged)? Existing HMP commands will still need the human > monitor support in order to handle old QEMU versions gracefully, but > I'm thinking about new commands only. Maybe it's a matter of terminology, but I have the impression you're talking about two things here: 1. HMP will always exist, in the meaning that qemu will always provide a human interface. If we move it to a python script or some kind of external process, that's an implementation detail. This means that, if you're adding new functionality to qemu and it does make sense for humans to use it, then it should have a HMP version. 2. If you do add the HMP interface, that's for humans to consume and its output/semantics should make sense for humans, not for management tools.

> Does everyone agree on this? I think this is an important discussion > if we want our management interface to get better and more consistent > in the future. > > Stefan >

On Thu, 15 Dec 2011 08:06:41 -0600 Anthony Liguori&lt;anthony(a)codemonkey.ws&gt; wrote: > There are still a lot of HMP commands that don't have an QMP analog. Luiz, it > might make sense to setup a wiki page which instructions on how to convert an > HMP command to a QMP command using QAPI. I wrote on how to write new QMP commands using the QAPI (docs/writing-qmp-commands.txt), going from there to a conversion shouldn't be difficult, but I can write a wiki page. Btw, counting with a series I haven't posted yet, we have less than 10 QMP commands left to be converted to the QAPI. I expect to start working on HMP conversions in January.

> If we did that, we could probably get more folks involved in the conversion process. That would be wonderful. > > Regards, > > Anthony Liguori > >> >>> Does everyone agree on this? I think this is an important discussion >>> if we want our management interface to get better and more consistent >>> in the future. >>> >>> Stefan >>> >> >> >