[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Qemu-devel] [PATCH v4 7/8] qmp: Support abstract classes on device-

From: Eduardo Habkost
Subject: Re: [Qemu-devel] [PATCH v4 7/8] qmp: Support abstract classes on device-list-properties
Date: Fri, 4 Nov 2016 14:04:21 -0200
User-agent: Mutt/1.7.0 (2016-08-17)

On Fri, Nov 04, 2016 at 04:45:17PM +0100, Markus Armbruster wrote:
> Eduardo Habkost <address@hidden> writes:
> > (CCing libvirt people, as I forgot to CC them)
> >
> > On Mon, Oct 31, 2016 at 03:07:23PM +0100, Igor Mammedov wrote:
> >> On Fri, 28 Oct 2016 23:48:06 -0200
> >> Eduardo Habkost <address@hidden> wrote:
> >> 
> >> > When an abstract class is used on device-list-properties, we can
> >> > simply return the class properties registered for the class.
> >> > 
> >> > This will be useful if management software needs to query for
> >> > supported options that apply to all devices of a given type (e.g.
> >> > options supported by all CPU models, options supported by all PCI
> >> > devices).
> >> Patch looks fine to me but I'm not qmp interface guru
> >> so I'd leave review up to maintainers.
> >> 
> >> One question though,
> >> How would management software discover typename of abstract class?
> >
> > It depends on the use case. On some cases, management may already
> > have bus-specific logic that will know what's the base type it
> > needs to query (e.g. it may query "pci-device" to find out if all
> > PCI devices support a given option). On other cases, it may be
> > discovered using other commands.
> The stated purpose of this feature is to let management software "query
> for supported options that apply to all devices of a given type".  I
> suspect that when management software has a notion of "a given type", it
> knows its name.
> Will management software go fishing for subtype relationships beyond the
> types it knows?  I doubt it.  Of course, management software developers
> are welcome to educate me :)
> > For the CPU case, I will propose adding the base QOM CPU typename
> > in the query-target command.
> Does this type name vary?  If yes, can you give examples?

It does. x86-specific CPU properties are on the x86_64-cpu and
i386-cpu classes. arm-specific CPU properties are on the arm-cpu

> >> Perhaps this patch should be part of some other series.
> >
> > This is a valid point. In this case, it depends on the approach
> > we want to take: do we want to provide a flexible interface for
> > management, let them find ways to make it useful and give us
> > feedback on what is lacking; or do we want to provide the new
> > interface only after we have specified the complete solution for
> > the problem?
> >
> > I don't know the answer. I will let the qdev/QOM/QMP maintainers
> > answer that.
> I'm reluctant to add QMP features just because we think they might be
> useful to someone.  We should talk to users to confirm our hunch before
> we act on it.
> That said, this one isn't exactly a biggie.

Considering we are past soft freeze, I can document a more
concrete usage example when I submit the next version.


reply via email to

[Prev in Thread] Current Thread [Next in Thread]