Re: [Qemu-devel] [RFC 0/2] Disable hotplug during migration

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

* Juan Quintela (quintela@redhat.com) wrote:
> Hi
> 
> This series disable hotplug/unplug during migration.  Thank to Markus
> for explaining where I had to put the checks.  Why?  Because during
> migration we will fail if there are changes.  For instance, in
> postcopy, if we add a memory region, we would failing.  Same for other
> devices if they are not setup exactly the same on destination.
> 
> Iidea would be to disable it, andthen enable for the thing that we know that work.
> 
> This series are on top of my previous RAMState v2 serie.
> 
> Commets, please?

So I think this is probably a good idea, but we should ask Li Zhijian who added
migration_bitmap_extend if the reason for adding it was because they
needed the hot add to work.
cc'd.

IMHO we really need a 'configuration change mutex' that you can take
to stop any changes in the VM hardware, and that would probably reduce
a lot of the places that hold the BQL for just stopping changes.

Dave

> 
> Thanks, Juan.
> 
> 
> Juan Quintela (2):
>   migration: Disable hotplug/unplug during migration
>   ram: remove migration_bitmap_extend()
> 
>  exec.c                  |  1 -
>  hw/core/qdev.c          |  5 +++++
>  include/exec/ram_addr.h |  2 --
>  migration/ram.c         | 34 ----------------------------------
>  qdev-monitor.c          |  7 ++++++-
>  5 files changed, 11 insertions(+), 38 deletions(-)
> 
> -- 
> 2.9.3
> 
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK