numa: introduce machine callback for VCPU to node mapping

Current default round-robin way of distributing VCPUs among
NUMA nodes might be wrong in case on multi-core/threads
CPUs. Making guests confused wrt topology where cores from
the same socket are on different nodes.

Allow a machine to override default mapping by providing
 MachineClass::cpu_index_to_socket_id()
callback which would allow it group VCPUs from a socket
on the same NUMA node.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Andreas Färber <afaerber@suse.de>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>

2 files changed, 7 insertions, 1 deletions

diff --git a/include/hw/boards.h b/include/hw/boards.h
index 1feea2b176..78838d13d4 100644
--- a/include/hw/boards.h
+++ b/include/hw/boards.h
@@ -82,6 +82,10 @@ bool machine_mem_merge(MachineState *machine);
  *    of HotplugHandler object, which handles hotplug operation
  *    for a given @dev. It may return NULL if @dev doesn't require
  *    any actions to be performed by hotplug handler.
+ * @cpu_index_to_socket_id:
+ *    used to provide @cpu_index to socket number mapping, allowing
+ *    a machine to group CPU threads belonging to the same socket/package
+ *    Returns: socket number given cpu_index belongs to.
  */
 struct MachineClass {
     /*< private >*/
@@ -118,6 +122,7 @@ struct MachineClass {
 
     HotplugHandler *(*get_hotplug_handler)(MachineState *machine,
                                            DeviceState *dev);
+    unsigned (*cpu_index_to_socket_id)(unsigned cpu_index);
 };
 
 /**
diff --git a/include/sysemu/numa.h b/include/sysemu/numa.h
index 5633b856a8..6523b4d7f9 100644
--- a/include/sysemu/numa.h
+++ b/include/sysemu/numa.h
@@ -6,6 +6,7 @@
 #include "qemu/option.h"
 #include "sysemu/sysemu.h"
 #include "sysemu/hostmem.h"
+#include "hw/boards.h"
 
 extern int nb_numa_nodes;   /* Number of NUMA nodes */
 
@@ -16,7 +17,7 @@ typedef struct node_info {
     bool present;
 } NodeInfo;
 extern NodeInfo numa_info[MAX_NODES];
-void parse_numa_opts(void);
+void parse_numa_opts(MachineClass *mc);
 void numa_post_machine_init(void);
 void query_numa_node_mem(uint64_t node_mem[]);
 extern QemuOptsList qemu_numa_opts;