Re: [Qemu-devel] [PATCH 4/6] hmp: Add info commands for preconfig

[Igor Mammedov <imammedo@redhat.com>]

On Thu, 07 Jun 2018 14:22:34 +0200
Markus Armbruster <armbru@redhat.com> wrote:

> Peter Xu <peterx@redhat.com> writes:
> 
> > On Tue, Jun 05, 2018 at 01:26:34PM +0100, Dr. David Alan Gilbert (git) wrote:  
> >> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
> >> 
> >> Allow a bunch of the info commands to be used in preconfig.
> >> Could probably add most of them.  
> >
> > I guess some of them may not work yet during preconfig.  E.g.:
> >
> > $ ./x86_64-softmmu/qemu-system-x86_64 -preconfig -monitor stdio
> > QEMU 2.12.50 monitor - type 'help' for more information
> > (qemu) info mtree
> > address-space: memory
> >   0000000000000000-ffffffffffffffff (prio 0, i/o): system
> >
> > address-space: I/O
> >   0000000000000000-000000000000ffff (prio 0, i/o): io
> >
> > But it's fine to enable that I guess.
> >
> > (Which "info" command would you want to use during preconfig?)
> >  
> >> 
> >> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>  
> >
> > Reviewed-by: Peter Xu <peterx@redhat.com>  
> 
> The reason for having -preconfig is us despairing of making -S do the
> right thing.  We'd have to *understand* the tangled mess that is our
> startup, and rearrange it so QMP becomes available early enough for
> configuring NUMA (and other things), yet late enough for everything to
> work.
We solve concrete NUMA problem at -S time as was demonstrated by thread:
"RFC v2 0/4] enable numa configuration before machine  is running from HMP/QMP"
were pros and cons are were summarized. But that won't scale to other things.
 
> -preconfig is a cheap hack to avoid this headache, by bypassing almost
> all of "everything".
hack should allow to move configuration steps to early stage one by one
until the point we could obsolete -S (from configuration point)
without breaking current -S users and clean up start up mess in process.

> Now you bring back some of "everything".  Dangerous.  You better show it
> actually works.  Until you do:
Tested v2, works as expected so far.

> 
> NAK
>