Re: [Qemu-devel] [RFC v0 0/2] Enforce gaps between DIMMs

[Igor Mammedov <imammedo@redhat.com>]

On Mon, 5 Oct 2015 23:24:33 +0300
"Michael S. Tsirkin" <mst@redhat.com> wrote:

> On Mon, Oct 05, 2015 at 02:05:22PM +0530, Bharata B Rao wrote:
> > The suggested way to work around the virtio bug reported here
> > 
> > http://lists.nongnu.org/archive/html/qemu-devel/2015-08/msg00522.html
> > 
> > is to introduce gaps between DIMMs. Igor's patchset changes the pc-dimm
> > auto-address assignment to introduce gaps and ues the same from pc memhp.
> > This patchset does the same for sPAPR PowerPC.
> > 
> > Before introducing the gap, ensure that memory hotplug region has enough
> > room for alignment adjustment. We accommodate a max alignment of 256MB for
> > each slot since sPAPR memory hotplug enforces an alignment requirement of
> > 256MB on RAM size, maxmem and NUMA node mem sizes.
> > 
> > This applies on David's spapr-next branch + Igor's patchset applied.
> > 
> > This has been very lightly tested and intention is to get feedback
> > on the correctness aspect of this.
> > 
> > Bharata B Rao (2):
> >   spapr: Accommadate alignment gaps in hotplug memory region
> >   spapr: Force gaps between DIMM's GPA
> 
> PC needs this, PPC needs this ... I don't see why would this not
> apply everywhere. Isn't it time we just converted everyone?
> Drop the gap flag, set it unconditionally for new machine types.
I guess that flag is needed exactly for compatibility with old
machine types which are per board thingy.

BTW:
does PPC have machine types? I don't see any compatibility
code in this series?

> 
> Thoughts?
> 
> 
> >  hw/ppc/spapr.c | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> > 
> > -- 
> > 2.1.0
> >