virtme-ng: introduce NUMA support

Add the --numa option to create custom NUMA nodes inside the guest and
assign virtual CPUs to them.

Syntax:

  --numa MEM[,cpus=FIRST_CPU1[-LAST_CPU1]][,cpus=FIRST_CPU2[-LAST_CPU2]]...

Example:

 $ vng -r -m 4G --numa 2G,cpus=0-1,cpus=3 --numa 2G,cpus=2,cpus=4-7 -- numactl -H
 available: 2 nodes (0-1)
 node 0 cpus: 0 1 3
 node 0 size: 2013 MB
 node 0 free: 1939 MB
 node 1 cpus: 2 4 5 6 7
 node 1 size: 1908 MB
 node 1 free: 1782 MB
 node distances:
 node   0   1
   0:  10  20
   1:  20  10

Keep in mind that using --numa automatically disables the microvm
architecture (that doesn't expose NUMA information).

Also note that virtiofsd requires a memory backed NUMA node, so if some
custom NUMA nodes are created virtiofs will use the first one of them,
otherwise it will create a single NUMA node that maps all the memory
(that was the previous behavior).

But this allows to use --numa and enable virtiofsd at the same time.

This implements the request from issue #56.

Signed-off-by: Andrea Righi <andrea.righi@canonical.com>

virtme/commands/run.py

@@ -151,6 +151,12 @@ def make_parser() -> argparse.ArgumentParser:
         default=None,
         help="Set guest memory and qemu -m flag.",
     )
+    g.add_argument(
+        "--numa",
+        action="append",
+        default=None,
+        help="Create NUMA nodes in the guest.",
+    )
     g.add_argument(
         "--cpus", action="store", default=None, help="Set guest cpu and qemu -smp flag."
     )
@@ -643,11 +649,14 @@ def export_virtiofs(
 
     # Adjust qemu options to use virtiofsd
     fsid = "virtfs%d" % len(qemuargs)
-    if memory is None:
-        memory = "128M"
+
     vhost_dev_type = arch.vhost_dev_type()
     qemuargs.extend(["-chardev", f"socket,id=char{fsid},path={virtio_fs.sock}"])
     qemuargs.extend(["-device", f"{vhost_dev_type},chardev=char{fsid},tag={mount_tag}"])
+    if memory is None:
+        memory = "128M"
+    elif memory == 0:
+        return True
     qemuargs.extend(["-object", f"memory-backend-memfd,id=mem,size={memory},share=on"])
     qemuargs.extend(["-numa", "node,memdev=mem"])
 
@@ -724,7 +733,7 @@ def can_use_kvm():
 
 
 def can_use_microvm(args):
-    return not args.disable_microvm and args.arch == "x86_64" and can_use_kvm()
+    return not args.disable_microvm and not args.numa and args.arch == "x86_64" and can_use_kvm()
 
 
 def has_read_acl(username, file_path):
@@ -799,6 +808,16 @@ def do_it() -> int:
             args.memory += "M"
         qemuargs.extend(["-m", args.memory])
 
+    # Parse NUMA settings.
+    if args.numa:
+        for i, numa in enumerate(args.numa, start=1):
+            size, cpus = numa.split(",", 1) if "," in numa else (numa, None)
+            cpus = f",{cpus}" if cpus else ""
+            qemuargs.extend([
+                "-object", f"memory-backend-memfd,id=mem{i},size={size},share=on",
+                "-numa", f"node,memdev=mem{i}{cpus}"
+            ])
+
     if args.snaps:
         if args.root == "/":
             snapd_state = "/var/lib/snapd/state.json"
@@ -853,7 +872,10 @@ def do_it() -> int:
             args.root,
             "ROOTFS",
             guest_tools_path=guest_tools_path,
-            memory=args.memory,
+            # virtiofsd requires a NUMA not, if --numa is specified simply use
+            # the user-defined NUMA node, otherwise create a NUMA node with all
+            # the memory.
+            memory=0 if args.numa else args.memory,
             verbose=args.verbose,
         )
         if can_use_microvm(args) and use_virtiofs:

virtme_ng/run.py

@@ -280,6 +280,13 @@ def make_parser():
         "--memory", "-m", action="store", help="Set guest memory size (qemu -m flag)"
     )
 
+    parser.add_argument(
+        "--numa",
+        metavar="MEM[,cpus=FIRST_CPU1[-LAST_CPU1]][,cpus=FIRST_CPU2[-LAST_CPU2]]...",
+        action="append",
+        help="Create NUMA nodes in the guest (this implicitly disables the microvm architecture)"
+    )
+
     parser.add_argument(
         "--balloon",
         action="store_true",
@@ -879,6 +886,13 @@ def _get_virtme_memory(self, args):
         else:
             self.virtme_param["memory"] = "--memory " + args.memory
 
+    def _get_virtme_numa(self, args):
+        if args.numa is not None:
+            numa_str = " ".join([f"--numa {numa}" for numa in args.numa])
+            self.virtme_param["numa"] = numa_str
+        else:
+            self.virtme_param["numa"] = ""
+
     def _get_virtme_balloon(self, args):
         if args.balloon:
             self.virtme_param["balloon"] = "--balloon"
@@ -948,6 +962,7 @@ def run(self, args):
         self._get_virtme_append(args)
         self._get_virtme_cpus(args)
         self._get_virtme_memory(args)
+        self._get_virtme_numa(args)
         self._get_virtme_balloon(args)
         self._get_virtme_snaps(args)
         self._get_virtme_busybox(args)
@@ -982,6 +997,7 @@ def run(self, args):
             + f'{self.virtme_param["append"]} '
             + f'{self.virtme_param["cpus"]} '
             + f'{self.virtme_param["memory"]} '
+            + f'{self.virtme_param["numa"]} '
             + f'{self.virtme_param["balloon"]} '
             + f'{self.virtme_param["snaps"]} '
             + f'{self.virtme_param["busybox"]} '