On 02/02/2018 08:50 AM, Eduardo Habkost wrote:
(CCing qemu-devel)
On Fri, Feb 02, 2018 at 09:21:59AM -0500, Luiz Capitulino wrote:
On Fri, 2 Feb 2018 14:19:38 +0000 Daniel P. Berrangé <berrange@redhat.com> wrote:
On Fri, Feb 02, 2018 at 12:15:54PM -0200, Eduardo Habkost wrote: [...]
It would be also interesting to update QEMU QMP documentation to clarify the arch-specific semantics of "halted".
Any also especially clarify the awful performance implications of running this particular query command. In general I would not expect query-xxx monitor commands to interrupt all vcpus, so we should clearly warn about this !
Or deprecate it...
We could deprecate the expensive fields on query-cpus, and move them to a more expensive query-cpu-state command. I believe most users of query-cpus are only interested in qom_path, thread_id, and topology info.
Markus, Eric: from the QAPI point of view, is it OK to remove fields between QEMU versions, as long as we follow our deprecation policy?
Removing an output field outright may break a client that depended on the field; so a deprecation period is definitely required there. But it is okay, documentation-wise, to state that a field is output always as 0 for back-compatibility reasons and that modern clients should ignore it (which would then let old clients still parse the field, but no longer see a non-zero value), whether or not we also pursue the deprecation course and eventually remove the field after more releases. See CpuInfo::current, for an example. -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org