On Thu, 14 Sep 2017 13:51:45 +0200 Michal Privoznik <mprivozn@xxxxxxxxxx> wrote: > On 09/14/2017 02:33 AM, Haozhong Zhang wrote: > > On 09/13/17 17:28 +0200, Michal Privoznik wrote: > >> > >> BTW: I ran a migration from no nvdimm qemu to one that had -M nvdimm=on > >> and guest migrated happily. So looks like guest ABI is stable (or at > >> least stable enough not to crash). But since ACPI table is changed I > >> doubt that. > > > > One example that may cause trouble is that > > 1/ Guest OS got a pointer to an ACPI table A on the source host (w/o nvdimm=on) > > 2/ After migrating to the destination host (w/ nvdimm=on), the > > location of ACPI table A is occupied by NFIT. If guest OS tries to > > access ACPI table A via the pointer in step 1/, then it will access > > the wrong table. > > > > Ah, you're right. So it a guest ABI breakage to add nvdimm=on. IOW, > libvirt can't safely add that onto command line. Well we could for > freshly started guest and not those which are just being migrated. But > that increases attack surface so it's not safe either. Okay, I'll stick > with the latest proposal (expose this in domain XML and let users turn > it on if they want to). also note that it depends on memory hotplug being enabled '-m xxx,slots+maxmem' -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list
