On 2011-12-15 14:53, Stefan Hajnoczi wrote:
On Thu, Dec 15, 2011 at 1:49 PM, Kevin Wolf <kwolf@redhat.com> 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.
Monitor pass-through via gdbstub requires text formatting on QEMU side. We could start providing a python plugin for gdb at some point that does the pretty printing on the client side, but moving over will be a lengthy process as well. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux