Re: [libvirt] [PATCH v2 82/86] numa: forbid '-numa node, mem' for 5.0 and newer machine types

[Igor Mammedov <imammedo@redhat.com>]

On Thu, 16 Jan 2020 13:06:28 +0000
Daniel P. Berrangé <berrange@redhat.com> wrote:

> On Thu, Jan 16, 2020 at 01:37:03PM +0100, Igor Mammedov wrote:
> > On Thu, 16 Jan 2020 11:42:09 +0100
> > Michal Privoznik <mprivozn@redhat.com> wrote:
> >   
> > > On 1/15/20 5:52 PM, Igor Mammedov wrote:  
> > > > On Wed, 15 Jan 2020 16:34:53 +0100
> > > > Peter Krempa <pkrempa@redhat.com> wrote:
> > > >     
> > > >> On Wed, Jan 15, 2020 at 16:07:37 +0100, Igor Mammedov wrote:    
> > > >>> Deprecation period is ran out and it's a time to flip the switch
> > > >>> introduced by cd5ff8333a.
> > > >>> Disable legacy option for new machine types and amend documentation.
> > > >>>
> > > >>> Signed-off-by: Igor Mammedov <imammedo@redhat.com>
> > > >>> ---
> > > >>> CC: peter.maydell@linaro.org
> > > >>> CC: ehabkost@redhat.com
> > > >>> CC: marcel.apfelbaum@gmail.com
> > > >>> CC: mst@redhat.com
> > > >>> CC: pbonzini@redhat.com
> > > >>> CC: rth@twiddle.net
> > > >>> CC: david@gibson.dropbear.id.au
> > > >>> CC: libvir-list@redhat.com
> > > >>> CC: qemu-arm@nongnu.org
> > > >>> CC: qemu-ppc@nongnu.org
> > > >>> ---
> > > >>>   hw/arm/virt.c        |  2 +-
> > > >>>   hw/core/numa.c       |  6 ++++++
> > > >>>   hw/i386/pc.c         |  1 -
> > > >>>   hw/i386/pc_piix.c    |  1 +
> > > >>>   hw/i386/pc_q35.c     |  1 +
> > > >>>   hw/ppc/spapr.c       |  2 +-
> > > >>>   qemu-deprecated.texi | 16 ----------------
> > > >>>   qemu-options.hx      |  8 ++++----
> > > >>>   8 files changed, 14 insertions(+), 23 deletions(-)    
> > > >>
> > > >> I'm afraid nobody bothered to fix it yet:
> > > >>
> > > >> https://bugzilla.redhat.com/show_bug.cgi?id=1783355    
> > > > 
> > > > It's time to start working on it :)
> > > > (looks like just deprecating stuff isn't sufficient motivation,
> > > > maybe actual switch flipping would work out better)
> > > >     
> > > 
> > > So how was the upgrade from older to newer version resolved? I mean, if 
> > > the old qemu used -numa node,mem=XXX and it is migrated to a host with 
> > > newer qemu, the cmd line can't be switched to -numa node,memdev=node0, 
> > > can it? I'm asking because I've just started working on this.  
> > 
> > see commit cd5ff8333a3c87 for detailed info.
> > Short answer is it's not really resolved [*],
> > -numa node,mem will keep working on newer QEMU but only for old machine types
> > new machine types will accept only -numa node,memdev.
> > 
> > One can check if "mem=' is supported by using QAPI query-machines
> > and checking numa-mem-supported field. That field is flipped to false
> > for 5.0 and later machine types in this patch.  
> 
> Since libvirt droppped the ball here, can we postpone this change
> to machine types until a later release. 

Looks like we have to at this point.
We can do this for [82-86/86] patches which are mostly numa
related changes.

The rest could go in this release as it is in-depended of
numa, it mainly introduces memdev backend for main RAM
and consolidates twisted main RAM allocation logic.

> 
> Regards,
> Daniel