Re: [RFC PATCH 1/2] softmmu/memory: add missing begin/commit callback calls

[Peter Xu]

On Fri, Aug 26, 2022 at 10:13:47AM -0400, Peter Xu wrote:
> On Fri, Aug 26, 2022 at 03:53:09PM +0200, Emanuele Giuseppe Esposito wrote:
> > What do you mean "will empty all regions with those listeners"?
> > But yes theoretically vhost-vdpa and physmem have commit callbacks that
> > are independent from whether region_add or other callbacks have been called.
> > For kvm and probably vhost it would be no problem, since there won't be
> > any list to iterate on.
> 
> Right, begin()/commit() is for address space update, so it should be fine
> to have nothing to commit, sorry.

Hold on..

When I was replying to your patch 2 and reading the code around, I fount
that this patch does affect vhost..  see region_nop() hook and also vhost's
version of vhost_region_addnop().  I think vhost will sync its memory
layout for each of the commit(), and any newly created AS could emptify
vhost memory list even if registered on address_space_memory.

The other thing is address_space_update_topology() seems to be only used by
address_space_init().  It means I don't think there should have any
listener registered to this AS anyway.. :) So iiuc this patch (even if
converting to loop over per-as memory listeners) is not needed.

-- 
Peter Xu