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
