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Re: [PULL 04/12] hmp: Simplify qom-set
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [PULL 04/12] hmp: Simplify qom-set |
Date: |
Wed, 3 Jun 2020 13:24:13 +0100 |
User-agent: |
Mutt/1.13.4 (2020-02-15) |
* David Hildenbrand (david@redhat.com) wrote:
> On 03.06.20 13:43, Dr. David Alan Gilbert wrote:
> > * David Hildenbrand (david@redhat.com) wrote:
> >> On 03.06.20 12:43, Dr. David Alan Gilbert wrote:
> >>> * David Hildenbrand (david@redhat.com) wrote:
> >>>> On 02.06.20 11:26, Dr. David Alan Gilbert wrote:
> >>>>> * Markus Armbruster (armbru@redhat.com) wrote:
> >>>>>> "Dr. David Alan Gilbert (git)" <dgilbert@redhat.com> writes:
> >>>>>>
> >>>>>>> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> >>>>>>>
> >>>>>>> Simplify qom_set by making it use qmp_qom_set and the JSON parser.
> >>>>>>>
> >>>>>>> (qemu) qom-get /machine smm
> >>>>>>> "auto"
> >>>>>>> (qemu) qom-set /machine smm "auto"
> >>>>>>>
> >>>>>>> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> >>>>>>> Message-Id: <20200520151108.160598-3-dgilbert@redhat.com>
> >>>>>>> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> >>>>>>> Reviewed-by: Markus Armbruster <armbru@redhat.com>
> >>>>>>> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
> >>>>>>> With 's'->'S' type change suggested by Paolo and Markus
> >>>>>>
> >>>>>> This is actually more than just simplification, it's disarming a bear
> >>>>>> trap: the string visitor is restricted to a subset of the QAPI types,
> >>>>>> and when you qom-set a property with a type it can't handle, QEMU
> >>>>>> aborts. I mentioned this in the discussion of possible ways out of the
> >>>>>> qom-get impasse, but missed reraising it in patch review.
> >>>>>>
> >>>>>> A suitably amended commit would be nice, but respinning the PR just for
> >>>>>> that may not be worthwhile.
> >>>>>
> >>>>> A bit late; still as long as we're removing bear traps not adding them.
> >>>>
> >>>> This breaks qom-set for my (virtio-mem) use case:
> >>>>
> >>>> echo "qom-set vm0 requested-size 300M" | sudo nc -U /var/tmp/mon_src
> >>>> QEMU 5.0.50 monitor - type 'help' for more information
> >>>> (qemu) qom-set vm0 requested-size 300M
> >>>> Error: Expecting at most one JSON value
> >>>
> >>> Does qom-set vm0 requested-size 300e6 do the same thing?
> >>
> >> The property is defined to be of type "size".
> >>
> >> (qemu) qom-set vm0 requested-size 300e6
> >> Error: Parameter 'requested-size' expects uint64
> >>
> >> (not sure how "size" and "uint64" are mapped here)
> >
> > I think the problem here is that the JSON parser is converting anything
> > with an 'e' as a float; JSON itself doesn't have the distinction
> > between int and float.
> >
>
> (and just to clarify - I assume you are aware - 300e6 != 300M. So the
> interface becomes way harder to use in case one wants to specify
> properly aligned sizes - 300M vs 314572800)
Oops, yes, good point.
I think on balance it's probably best that this keeps supporting JSON;
although tbh I'm not convinced there are any complex types that can be
set.
I'm not seeing a prettier answer.
Dave
>
> --
> Thanks,
>
> David / dhildenb
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
- [PULL 03/12] hmp: Implement qom-get HMP command, (continued)
- [PULL 03/12] hmp: Implement qom-get HMP command, Dr. David Alan Gilbert (git), 2020/06/01
- [PULL 04/12] hmp: Simplify qom-set, Dr. David Alan Gilbert (git), 2020/06/01
- Re: [PULL 04/12] hmp: Simplify qom-set, Markus Armbruster, 2020/06/02
- Re: [PULL 04/12] hmp: Simplify qom-set, Dr. David Alan Gilbert, 2020/06/02
- Re: [PULL 04/12] hmp: Simplify qom-set, David Hildenbrand, 2020/06/03
- Re: [PULL 04/12] hmp: Simplify qom-set, Dr. David Alan Gilbert, 2020/06/03
- Re: [PULL 04/12] hmp: Simplify qom-set, David Hildenbrand, 2020/06/03
- Re: [PULL 04/12] hmp: Simplify qom-set, David Hildenbrand, 2020/06/03
- Re: [PULL 04/12] hmp: Simplify qom-set, Dr. David Alan Gilbert, 2020/06/03
- Re: [PULL 04/12] hmp: Simplify qom-set, David Hildenbrand, 2020/06/03
- Re: [PULL 04/12] hmp: Simplify qom-set,
Dr. David Alan Gilbert <=
- Re: [PULL 04/12] hmp: Simplify qom-set, David Hildenbrand, 2020/06/03
- Re: [PULL 04/12] hmp: Simplify qom-set, David Hildenbrand, 2020/06/03
- Re: [PULL 04/12] hmp: Simplify qom-set, Dr. David Alan Gilbert, 2020/06/03
[PULL 01/12] migration/rdma: fix potential nullptr access in rdma_start_incoming_migration, Dr. David Alan Gilbert (git), 2020/06/01
[PULL 05/12] virtiofsd: remove symlink fallbacks, Dr. David Alan Gilbert (git), 2020/06/01
[PULL 08/12] migration/colo.c: Use cpu_synchronize_all_states(), Dr. David Alan Gilbert (git), 2020/06/01
[PULL 06/12] migration/vmstate: Remove unnecessary MemoryRegion forward declaration, Dr. David Alan Gilbert (git), 2020/06/01
[PULL 09/12] migration/colo.c: Flush ram cache only after receiving device state, Dr. David Alan Gilbert (git), 2020/06/01
[PULL 10/12] migration/colo.c: Relaunch failover even if there was an error, Dr. David Alan Gilbert (git), 2020/06/01
[PULL 07/12] migration/colo.c: Use event instead of semaphore, Dr. David Alan Gilbert (git), 2020/06/01