[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH] spapr: Don't support query-hotpluggable-cpus on
From: |
Igor Mammedov |
Subject: |
Re: [Qemu-devel] [PATCH] spapr: Don't support query-hotpluggable-cpus on earlier pseries machine types |
Date: |
Tue, 2 Aug 2016 10:13:19 +0200 |
On Tue, 2 Aug 2016 16:20:50 +1000
David Gibson <address@hidden> wrote:
> On Tue, Aug 02, 2016 at 10:34:34AM +0530, Bharata B Rao wrote:
> > On Tue, Aug 02, 2016 at 02:25:08PM +1000, David Gibson wrote:
> > > On Power, support for vCPU hotplug is new in qemu 2.7. However, we
> > > currently implement the query_hotpluggable_cpus hook the same for all
> > > pseries machine type versions.
> > >
> > > However, the old-style CPU initialization doesn't work with the new query
> > > code, meaning that attempting to use query-hotpluggable-cpus on a
> > > pseries-2.6 or earlier VM will cause qemu to SEGV.
> > >
> > > This fixes the problem by simply disabling the hook for earlier machine
> > > types.
> >
> > I had sent a patch to fix this and a couple of other related issues
> > some time back and it indeed was accepted into your ppc-for-2.7 branch.
> >
> > https://lists.gnu.org/archive/html/qemu-devel/2016-07/msg01539.html
> >
> > Only now I am realizing that somehow that patch didn't make it to mainline.
> >
>
> Oh.. good point. Sorry, that one somehow slipped through the cracks.
>
> So, the remaining question is, what's the preferred behaviour for
> older machine types:
>
> 1) should query-hotpluggable-cpus give an error, the same as it does
> on machine types which have never supported it (this is what my
> patch does)
>
> or
>
> 2) Should query-hotpluggable-cpus succeed, but return an empty list?
> (this is what Bharata's patch does)
>
> Igor and / or Peter, do you have an opinion on which behaviour is preferable?
>
If it doesn't have any output then it makes sense to set handler to NULL
so it would return error.