Il 17/09/2013 16:45, Michael S. Tsirkin ha scritto: > On Tue, Sep 17, 2013 at 04:41:45PM +0200, Paolo Bonzini wrote: >> Il 17/09/2013 14:47, Michael S. Tsirkin ha scritto: >>> Ergo, to make sure a referenced MR does not get >>> destroyed, we must make sure only finalize >>> calls memory_region_destroy. >>> >>> So I think this patchset should do exactly that, >>> not try to move out more stuff to finalize. >> >> Yes, this is the part of the problem that applies to all devices. >> >> Some devices may have timers or other dynamically-allocated data that >> may be used between exit and finalize. The same applies to capabilities >> such as MSI and MSI-X. All this must also be moved to finalize, but >> this can be done in separate patches. >> >> I'll separate the series as follows: >> >> - memory_region_destroy >> >> - unregister_savevm > > What's the problem here exactly?
I was thinking about AIO callbacks here, but we don't support device hot(un)plug during migration so I can remove this part. >> - other dynamically allocated data > > And here? I don't think we should move rundom stuff out to finalize > just because we can. It's not random stuff, AIO callbacks can access dynamically allocated data between exit and finalize. Even if a particular device doesn't do it, there's no hope of having best practices from contributors if we do not do things consistently. >> - del_vm_change_state_handler Same here: user can stop/cont between exit and finalize, for example because the I/O failed. Paolo >> - MSI-X >> >> - SHPC, AER and other PCI/bridge stuff >> >> Paolo > > Let's document specific problems and fix them. > Randomly moving cleanup order has a high chance to > introduce bugs. >
