numa: deprecate 'mem' parameter of '-numa node' option

The parameter allows to configure fake NUMA topology where guest
VM simulates NUMA topology but not actually getting performance
benefits from it. The same or better results could be achieved
using 'memdev' parameter.
Beside of unpredictable performance, '-numa node.mem' option has
other issues when it's used with combination of -mem-path +
+ -mem-prealloc + memdev backends (pc-dimm), breaking binding of
memdev backends since mem-path/mem-prealloc are global and affect
the most of RAM allocations.

It's possible to make memdevs and global -mem-path/mem-prealloc
to play nicely together but that will just complicate already
complicated code and add unobious ways it could break on 2
different memmory allocation pathes and their combinations.

Instead of it, consolidate all guest RAM allocation over memdev
which still allows to create fake NUMA configurations if desired
and leaves one simplifyed code path to consider when it comes
to guest RAM allocation.

To achieve desired simplification deprecate 'mem' parameter as its
ad-hoc partitioning of initial RAM MemoryRegion can't be translated
to memdev based backend transparently to users and in compatible
manner (migration wise).

Later down the road that will allow to consolidate means of how
guest RAM is allocated and would permit us to clean up quite
a bit memory allocations and numa code, leaving only 'memdev'
implementation in place.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <1559205199-233510-3-git-send-email-imammedo@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/hw/core/numa.c b/hw/core/numa.c
index 4252af7100..b9e79b8c8b 100644
--- a/hw/core/numa.c
+++ b/hw/core/numa.c
@@ -118,6 +118,8 @@ static void parse_numa_node(MachineState *ms, NumaNodeOptions *node,
 
     if (node->has_mem) {
         numa_info[nodenr].node_mem = node->mem;
+        warn_report("Parameter -numa node,mem is deprecated,"
+                    " use -numa node,memdev instead");
     }
     if (node->has_memdev) {
         Object *o;