From: Eduardo Habkost <ehabkost@redhat.com>
To: Igor Mammedov <imammedo@redhat.com>
Cc: Damien Hedde <damien.hedde@greensocs.com>,
Peter Maydell <peter.maydell@linaro.org>,
QEMU Developers <qemu-devel@nongnu.org>,
Stefan Hajnoczi <stefanha@redhat.com>,
Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: qom device lifecycle interaction with hotplug/hotunplug ?
Date: Fri, 29 Nov 2019 16:53:43 -0300 [thread overview]
Message-ID: <20191129195343.GF14595@habkost.net> (raw)
In-Reply-To: <20191129134055.08f27e7a@redhat.com>
On Fri, Nov 29, 2019 at 01:40:55PM +0100, Igor Mammedov wrote:
> On Thu, 28 Nov 2019 13:33:58 -0300
> Eduardo Habkost <ehabkost@redhat.com> wrote:
>
> > On Thu, Nov 28, 2019 at 04:00:06PM +0000, Peter Maydell wrote:
> > > Hi; this is a question which came up in Damien's reset series
> > > which I don't know the answer to:
> > >
> > > What is the interaction of the QOM device lifecycle (instance_init/realize/
> > > unrealize/instance_finalize) with hotplug and hot-unplug ? I couldn't
> > > find any documentation of this but maybe I was looking in the wrong
> > > place...
> > >
> > > Looking at device_set_realized() it seems like we treat "realize"
> > > as meaning "and also do the hot-plug if this is a device we're
> > > trying to hotplug". On the other hand hot-unplug is I think the
> > > other way around: when we get a hot-unplug event we assume that
> > > it should also imply an "unrealize" (but just unrealizing doesn't
> > > auto-hot-unplug) ?
> >
> > Your description seems accurate, and I agree it is confusing.
> >
> > It would be more consistent if realized=true didn't plug the
> > device automatically, and qdev_device_add() asked the hotplug
> > handler to plug the device instead.
> agreed, it's confusing. But that would not allow to
> o = object_new()
> set props
> o.realize()
> reuse the same plug handlers.
>
I thought we had very few places that set realized=true directly,
so changing this behavior would be easy.
I was mistaken. Grepping for 'set_bool.*"realized"' found more
than 300 matches.
> we potentially can convert it to device_add input arguments
> and then call qdev_device_add() instead, which would then
> handle plug handlers, not sure it's doable though.
> Other than that I don't have any ideas how to make it less confusing.
We could introduce a "plugged" property which implicitly calls
the hotplug handler, and run a global s/"realized"/"plugged"/
substitution in the whole tree. Would it be worth the trouble,
though?
--
Eduardo
next prev parent reply other threads:[~2019-11-29 19:57 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-28 16:00 qom device lifecycle interaction with hotplug/hotunplug ? Peter Maydell
2019-11-28 16:33 ` Eduardo Habkost
2019-11-29 12:40 ` Igor Mammedov
2019-11-29 19:53 ` Eduardo Habkost [this message]
2019-11-28 17:27 ` Igor Mammedov
2019-11-28 17:57 ` Peter Maydell
2019-11-29 12:26 ` Igor Mammedov
2019-11-29 12:45 ` Peter Maydell
2019-11-29 13:05 ` Damien Hedde
2019-11-29 14:23 ` Igor Mammedov
2019-11-29 20:05 ` Eduardo Habkost
2019-11-30 11:10 ` Peter Maydell
2019-12-03 21:40 ` Eduardo Habkost
2019-12-04 9:18 ` Jens Freimann
2019-12-04 14:35 ` Eduardo Habkost
2019-12-04 16:21 ` Jens Freimann
2019-12-04 18:51 ` Eduardo Habkost
2019-12-11 12:52 ` Damien Hedde
2019-12-18 15:14 ` Jens Freimann
2019-12-11 16:01 ` Igor Mammedov
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