On Thu, Oct 02, 2014 at 03:43:35PM +0200, Paolo Bonzini wrote: > Il 02/10/2014 15:41, Michael S. Tsirkin ha scritto: > > On Thu, Oct 02, 2014 at 03:30:57PM +0200, Paolo Bonzini wrote: > >> These patches do fix John's scenario, but that is not the main issue. > >> They are not an _attempt_ to fix it, they just do so more or less by > >> chance. Their real purpose is fixing the second issue: > >> > >>> - table size changes cause cross version migration issues > >>> this is really due to the fact we are using RAM > >>> to migrate ACPI tables. > >>> IMHO a more robust fix would be to allow RAM size to change > >>> during migration, or to avoid using RAM, switch to another type of > >>> object. > >> > >> Allowing fw_cfg size to change during migration (does not matter if it > >> is stored in RAM or otherwise) is a huge can of worms because the host > >> might have loaded the size and stored it somewhere, way before migration. > > > > Right. I'm not suggesting it. I suggest migrating fw cfg size instead. > > > > The issue is that incoming migration might have a different > > fw_cfg size from what we have. > > Understood now. > > > I think migrating this value will solve the issue in a cleaner way. > > Perhaps. The question is whether it would complicate the > forwards-migration code beyond what is sane. I think we are practically > speaking stuck with RAM. > > Paolo
Migrating RAM size is actually useful too, I think someone asked for it. -- MST
