[Qemu-devel] [PATCH v4 0/3] numa: deprecate '-numa node, mem' and default memory distribution

[Igor Mammedov <imammedo@redhat.com>]

Changes since v3:
  - simplify series by dropping idea of showing property values in "qom-list-properties"
    and use MachineInfo in QAPI schema instead

Changes since v2:
  - taking in account previous review, implement a way for mgmt to intospect if
    '-numa node,mem' is supported by machine type as suggested by Daniel at
             https://www.mail-archive.com/qemu-devel@nongnu.org/msg601220.html
      * ammend "qom-list-properties" to show property values
      * add "numa-mem-supported" machine property to reflect if '-numa node,mem=SZ'
        is supported. It culd be used with '-machine none' or at runtime with
        --preconfig before numa memory mapping are configured
  * minor fixes to deprecation documentation mentioning "numa-mem-supported" property

 1) "I'm considering to deprecating -mem-path/prealloc CLI options and replacing
them with a single memdev Machine property to allow interested users to pick
used backend for initial RAM (fixes mixed -mem-path+hostmem backends issues)
and as a transition step to modeling initial RAM as a Device instead of
(ab)using MemoryRegion APIs."
(for more details see: https://www.mail-archive.com/qemu-devel@nongnu.org/msg596314.html)

However there is a couple of roadblocks on the way (s390x and numa memory handling).
I think I finally thought out a way to hack s390x in migration compatible manner,
but I don't see any way to do it for -numa node,mem and default RAM assignement
to nodes. Considering both numa usecases aren't meaningfully using NUMA (aside
guest side testing) and could be replaced with explicitly used memdev parameter,
I'd like to propose removing these fake NUMA friends on new machine types,
hence this deprecation. And once the last machie type that supported the option
is removed we would be able to remove option altogether.

As result of removing deprecated options and replacing initial RAM allocation
with 'memdev's (1), QEMU will allocate guest RAM in consistent way, fixing mixed
use-case and allowing boards to move towards modelling initial RAM as Device(s).
Which in its own turn should allow to cleanup NUMA/HMP/memory accounting code
more by dropping ad-hoc node_mem tracking and reusing memory device enumeration
instead.

Reference to previous versions:
 * https://www.mail-archive.com/qemu-devel@nongnu.org/msg617694.html

CC: libvir-list@redhat.com
CC: ehabkost@redhat.com
CC: pbonzini@redhat.com
CC: berrange@redhat.com
CC: armbru@redhat.com

Igor Mammedov (3):
  machine: show if CLI option '-numa node,mem' is supported in QAPI
    schema
  numa: deprecate 'mem' parameter of '-numa node' option
  numa: deprecate implict memory distribution between nodes

 include/hw/boards.h  |  3 +++
 hw/arm/virt.c        |  1 +
 hw/i386/pc.c         |  1 +
 hw/ppc/spapr.c       |  1 +
 numa.c               |  5 +++++
 qapi/misc.json       |  5 ++++-
 qemu-deprecated.texi | 24 ++++++++++++++++++++++++
 vl.c                 |  1 +
 8 files changed, 40 insertions(+), 1 deletion(-)

-- 
2.7.4