* Stefan Hajnoczi (stefa...@gmail.com) wrote: > On Wed, Aug 23, 2017 at 02:51:03PM +0800, Peter Xu wrote: > > The root problem is that, monitor commands are all handled in main > > loop thread now, no matter how many monitors we specify. And, if main > > loop thread hangs due to some reason, all monitors will be stuck. > > I see a larger issue with postcopy: existing QEMU code assumes that > guest memory access is instantaneous. > > Postcopy breaks this assumption and introduces blocking points that can > now take unbounded time. > > This problem isn't specific to the monitor. It can also happen to other > components in QEMU like the gdbstub. > > Do we need an asynchronous memory API? Synchronous memory access should > only be allowed in vcpu threads.
It would probably be useful for gdbstub where the overhead of async doesn't matter; but doing that for all IO emulation is hard. Dave > Stefan -- Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
