Re: [Qemu-devel] [PATCH v4 4/6] vhost: add regions to temporary list

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* Paolo Bonzini (pbonzini@redhat.com) wrote:
> On 15/12/2017 14:30, Dr. David Alan Gilbert wrote:
> >> Also it seems that we have a race in current code where
> >> region_del() unrefs memory region first and then by the
> >> commit time memory region could be gone since old flatview
> >> is unreffed before commit callback is called, but guest still
> >> uses old memory map until vhost_set_mem_table() is complete.
> >> We probably should unref deleted(old) sections after
> >> guest gets new memmap.
> >
> > Will they really get cleaned up before the commit() returns?
> > There's no rcu like thing guarding it?
> 
> The memory subsystem only keeps them alive until before commmit() is
> invoked.

Hmm ok; I guess then we do need to keep the temporary list of
MemoryRegionSections and unref all the old ones after the end of the callback.

I'll rework it (again).

Dave


> Paolo
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK