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Re: [Qemu-devel] [PATCH 4/6] hmp: Add info commands for preconfig
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [PATCH 4/6] hmp: Add info commands for preconfig |
Date: |
Fri, 8 Jun 2018 18:18:57 +0100 |
User-agent: |
Mutt/1.9.5 (2018-04-13) |
* Markus Armbruster (address@hidden) wrote:
> "Dr. David Alan Gilbert" <address@hidden> writes:
>
> > * Markus Armbruster (address@hidden) wrote:
> >> "Dr. David Alan Gilbert" <address@hidden> writes:
> >>
> >> > * Markus Armbruster (address@hidden) wrote:
> >> >> "Dr. David Alan Gilbert" <address@hidden> writes:
> >> >>
> >> >> > * Markus Armbruster (address@hidden) wrote:
> >> >> >> Peter Xu <address@hidden> writes:
> >> >> >>
> >> >> >> > On Tue, Jun 05, 2018 at 01:26:34PM +0100, Dr. David Alan Gilbert
> >> >> >> > (git) wrote:
> >> >> >> >> From: "Dr. David Alan Gilbert" <address@hidden>
> >> >> >> >>
> >> >> >> >> Allow a bunch of the info commands to be used in preconfig.
> >> >> >> >> Could probably add most of them.
> >> >> >> >
> >> >> >> > I guess some of them may not work yet during preconfig. E.g.:
> >> >> >> >
> >> >> >> > $ ./x86_64-softmmu/qemu-system-x86_64 -preconfig -monitor stdio
> >> >> >> > QEMU 2.12.50 monitor - type 'help' for more information
> >> >> >> > (qemu) info mtree
> >> >> >> > address-space: memory
> >> >> >> > 0000000000000000-ffffffffffffffff (prio 0, i/o): system
> >> >> >> >
> >> >> >> > address-space: I/O
> >> >> >> > 0000000000000000-000000000000ffff (prio 0, i/o): io
> >> >> >> >
> >> >> >> > But it's fine to enable that I guess.
> >> >> >> >
> >> >> >> > (Which "info" command would you want to use during preconfig?)
> >> >> >> >
> >> >> >> >>
> >> >> >> >> Signed-off-by: Dr. David Alan Gilbert <address@hidden>
> >> >> >> >
> >> >> >> > Reviewed-by: Peter Xu <address@hidden>
> >> >> >>
> >> >> >> The reason for having -preconfig is us despairing of making -S do the
> >> >> >> right thing. We'd have to *understand* the tangled mess that is our
> >> >> >> startup, and rearrange it so QMP becomes available early enough for
> >> >> >> configuring NUMA (and other things), yet late enough for everything
> >> >> >> to
> >> >> >> work.
> >> >> >>
> >> >> >> -preconfig is a cheap hack to avoid this headache, by bypassing
> >> >> >> almost
> >> >> >> all of "everything".
> >> >> >>
> >> >> >> Now you bring back some of "everything". Dangerous. You better
> >> >> >> show it
> >> >> >> actually works. Until you do:
> >> >> >>
> >> >> >> NAK
> >> >> >
> >> >> > Well I did test each command in here to make sure it didn't
> >> >> > crash/produce complete junk; but here's the output with the v2 of this
> >> >> > patch that Igor R-b:
> >> >> [...]
> >> >>
> >> >> For the sake of the argument, let's assume these commands all work in
> >> >> preconfig state. Are their QMP equivalents all available in preconfig
> >> >> state?
> >> >
> >> > That I don't know; I was happy to fix my list to the ones
> >> > Igor recommended. If you object to some particular entries I'll
> >> > be happy to change them.
> >>
> >> HMP must not provide more functionality than QMP. Specifically, we may
> >> provide "info FOO" only when we also provide query-FOO.
> >>
> >> There are exceptions to this rule. I don't think they apply here. I'm
> >> prepared to discuss them, of course.
> >
> > No, that's strictly not true; HMP can provide anything that helps
> > a human debug stuff.
>
> Yes, but...
>
> > The requirement is that if a tool needs it then it
> > must be provided in QMP.
>
> ... it must not do that at the expense of QMP's completeness.
> Permitting that would be a break from how we worked since QMP became
> supported in 0.14 or so. Seven years, time flies.
>
> The hard requirement for QMP from day one was "provide everything
> machine clients need". To avoid speculation and endless arguments about
> what might be needed / not needed, we resolved to approximate this by
> "provide everything, except stuff that's *clearly* of no use to
> machines". This has been spelled out on this list several times.
> Here are two relatively recent iterations:
>
> Message-ID: <address@hidden>
> https://lists.gnu.org/archive/html/qemu-devel/2017-04/msg05309.html
>
> Message-ID: <address@hidden>
> https://lists.gnu.org/archive/html/qemu-devel/2017-05/msg00247.html
>
> Quoting the latter:
>
> In general, functionality available in HMP should also available in QMP.
> Exceptions include functionality that makes no sense in QMP, or is of
> use only for human users. If you think your command is an exception,
> please explain why in the commit message.
>
> If it isn't, you need to implement it for QMP (including suitable test
> cases), then rewrite the HMP version to reuse either the QMP command or
> a common core.
>
> Example for "makes no sense in QMP": setting the current CPU[1], because
> a QMP monitor doesn't have a current CPU.
>
> Examples for "is of use only for human users": HMP command "help", the
> integrated pocket calculator[2].
>
> End quote.
>
> But we're not even arguing about a new HMP command, we're arguing about
> making existing commands available in preconfig state. I assume that if
> an HMP command is useful in preconfig state, then its QMP buddy is also
> useful there. I therefore asked you whether their QMP equivalents are
> all available in preconfig state. The answer I expected was a short
> table of three columns: HMP command you propose to enable, QMP buddy if
> any, whether the QMP buddy is available in preconfig state yes/no.
> Estimated effort: minutes. What I got instead of this data was an
> argument about fundamental design decisions. Fine, reexaminating
> fundamentals once in a while isn't a bad idea. But may I have my data
> now?
I believe that table is in the v3 version patch 5.
Dave
> [...]
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK
- [Qemu-devel] [PATCH 4/6] hmp: Add info commands for preconfig, (continued)
- [Qemu-devel] [PATCH 4/6] hmp: Add info commands for preconfig, Dr. David Alan Gilbert (git), 2018/06/05
- Re: [Qemu-devel] [PATCH 4/6] hmp: Add info commands for preconfig, Peter Xu, 2018/06/07
- Re: [Qemu-devel] [PATCH 4/6] hmp: Add info commands for preconfig, Markus Armbruster, 2018/06/07
- Re: [Qemu-devel] [PATCH 4/6] hmp: Add info commands for preconfig, Dr. David Alan Gilbert, 2018/06/07
- Re: [Qemu-devel] [PATCH 4/6] hmp: Add info commands for preconfig, Markus Armbruster, 2018/06/07
- Re: [Qemu-devel] [PATCH 4/6] hmp: Add info commands for preconfig, Dr. David Alan Gilbert, 2018/06/07
- Re: [Qemu-devel] [PATCH 4/6] hmp: Add info commands for preconfig, Markus Armbruster, 2018/06/08
- Re: [Qemu-devel] [PATCH 4/6] hmp: Add info commands for preconfig, Dr. David Alan Gilbert, 2018/06/08
- Re: [Qemu-devel] [PATCH 4/6] hmp: Add info commands for preconfig, Igor Mammedov, 2018/06/08
- Re: [Qemu-devel] [PATCH 4/6] hmp: Add info commands for preconfig, Markus Armbruster, 2018/06/08
- Re: [Qemu-devel] [PATCH 4/6] hmp: Add info commands for preconfig,
Dr. David Alan Gilbert <=
- Re: [Qemu-devel] [PATCH 4/6] hmp: Add info commands for preconfig, Igor Mammedov, 2018/06/07
- Re: [Qemu-devel] [PATCH 4/6] hmp: Add info commands for preconfig, Markus Armbruster, 2018/06/08
Re: [Qemu-devel] [PATCH 4/6] hmp: Add info commands for preconfig, Igor Mammedov, 2018/06/07
[Qemu-devel] [PATCH 5/6] hmp: add exit_preconfig, Dr. David Alan Gilbert (git), 2018/06/05
[Qemu-devel] [PATCH 6/6] hmp: Allow HMP in preconfig state again, Dr. David Alan Gilbert (git), 2018/06/05
Re: [Qemu-devel] [PATCH 0/6] Reenable hmp for preconfig mode, Peter Xu, 2018/06/07