Re: [Qemu-devel] An emulation failure occurs, if I hotplug vcpus immediately after the VM start

[Paolo Bonzini]

On 07/06/2018 12:37, David Hildenbrand wrote:
> 
> I have a related requirement, which would be to atomically grow a
> memory regions. So instead of region_del(old)+region_add(new), I would
> have to do it in one shot (atomically).
> 
> AFAICS an atomic replace of the memory map would work for this, too.
> However I am not sure how we want to handle all kinds of tracking data
> that is connected to e.g. x86 memory slots (e.g. rmap, dirty bitmap ...).

The dirty bitmap would be synced in kvm_region_del (so it's not true
that kvm_region_del would disappear, but almost :)).

The rmap is more interesting.  Perhaps it can be just rebuilt on every
KVM_SET_USER_MEMORY_REGIONS call.

Paolo