>
> > >
> > >> + /* we will need a new memory slot for kvm and vhost */
> > >> + if (kvm_enabled() && !kvm_has_free_slot(machine)) {
> > >> + error_setg(errp, "hypervisor has no free memory slots left");
> > >> + return;
> > >> + }
> > >> + if (!vhost_has_free_slot()) {
> > >> + error_setg(errp, "a used vhost backend has no free memory slots
> > >> left");
> > >> + return;
> > >> + }
> > > move these checks to pre_plug time
> > >
> > >> +
> > >> + memory_region_add_subregion(&hpms->mr, addr - hpms->base, mr);
> > > missing vmstate registration?
> >
> > Missed this one: To be called by the caller. Important because e.g. for
> > virtio-pmem we don't want this (I assume :) ).
> if pmem isn't on shared storage, then We'd probably want to migrate
> it as well, otherwise target would experience data loss.
> Anyways, I'd just reat it as normal RAM in migration case
Main difference between RAM and pmem it acts like combination of RAM and disk.
Saying this, in normal use-case size would be 100 GB's - few TB's range.
I am not sure we really want to migrate it for non-shared storage use-case.
One reason why nvdimm added vmstate info could be: still there would be
transient
writes in memory with fake DAX and there is no way(till now) to flush the guest
writes. But with virtio-pmem we can flush such writes before migration and
automatically
at destination host with shared disk we will have updated data.
Thanks,
Pankaj
