conf: Disallow nonexistent NUMA nodes for hugepages

As of 136ad4974 it is possible to specify different huge pages per
guest NUMA node. However, there's no check if nodeset specified in
./hugepages/page contains only those guest NUMA nodes that exist.
In other words with current code it is possible to define meaningless
combination:

  <memoryBacking>
    <hugepages>
      <page size='1048576' unit='KiB' nodeset='0,2-3'/>
      <page size='2048' unit='KiB' nodeset='1,4'/>
    </hugepages>
  </memoryBacking>
  <vcpu placement='static'>4</vcpu>
  <cpu>
    <numa>
      <cell id='0' cpus='0' memory='1048576'/>
      <cell id='1' cpus='1' memory='1048576'/>
      <cell id='2' cpus='2' memory='1048576'/>
      <cell id='3' cpus='3' memory='1048576'/>
    </numa>
  </cpu>

Notice the node 4 in <hugepages/>?

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>

src/qemu/qemu_command.c

@@ -6550,6 +6550,30 @@ qemuBuildNumaArgStr(virQEMUDriverConfigPtr cfg,
         goto cleanup;
     }
 
+    for (i = 0; i < def->mem.nhugepages; i++) {
+        ssize_t next_bit, pos = 0;
+
+        if (!def->mem.hugepages[i].nodemask) {
+            /* This is the master hugepage to use. Skip it as it has no
+             * nodemask anyway. */
+            continue;
+        }
+
+        if (def->cpu && def->cpu->ncells) {
+            /* Fortunately, we allow only guest NUMA nodes to be continuous
+             * starting from zero. */
+            pos = def->cpu->ncells - 1;
+        }
+
+        next_bit = virBitmapNextSetBit(def->mem.hugepages[i].nodemask, pos);
+        if (next_bit >= 0) {
+            virReportError(VIR_ERR_XML_DETAIL,
+                           _("hugepages: node %zd not found"),
+                           next_bit);
+            goto cleanup;
+        }
+    }
+
     for (i = 0; i < def->cpu->ncells; i++) {
         int cellmem = VIR_DIV_UP(def->cpu->cells[i].mem, 1024);
         def->cpu->cells[i].mem = cellmem * 1024;

tests/qemuxml2argvdata/qemuxml2argv-hugepages-pages4.xml

@@ -0,0 +1,45 @@
+<domain type='qemu'>
+  <name>QEMUGuest1</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>4194304</memory>
+  <currentMemory unit='KiB'>4194304</currentMemory>
+  <memoryBacking>
+    <hugepages>
+      <page size='2048' unit='KiB' nodeset='1,4'/>
+      <page size='1048576' unit='KiB' nodeset='0,2-3'/>
+    </hugepages>
+  </memoryBacking>
+  <vcpu placement='static'>4</vcpu>
+  <numatune>
+    <memory mode='strict' nodeset='0-3'/>
+    <memnode cellid='3' mode='strict' nodeset='3'/>
+  </numatune>
+  <os>
+    <type arch='i686' machine='pc'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <cpu>
+    <numa>
+      <cell id='0' cpus='0' memory='1048576'/>
+      <cell id='1' cpus='1' memory='1048576'/>
+      <cell id='2' cpus='2' memory='1048576'/>
+      <cell id='3' cpus='3' memory='1048576'/>
+    </numa>
+  </cpu>
+  <clock offset='utc'/>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>destroy</on_crash>
+  <devices>
+    <emulator>/usr/bin/qemu</emulator>
+    <disk type='block' device='disk'>
+      <source dev='/dev/HostVG/QEMUGuest1'/>
+      <target dev='hda' bus='ide'/>
+      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
+    </disk>
+    <controller type='usb' index='0'/>
+    <controller type='ide' index='0'/>
+    <controller type='pci' index='0' model='pci-root'/>
+    <memballoon model='virtio'/>
+  </devices>
+</domain>

tests/qemuxml2argvtest.c

@@ -686,6 +686,8 @@ mymain(void)
             QEMU_CAPS_OBJECT_MEMORY_FILE);
     DO_TEST("hugepages-shared", QEMU_CAPS_MEM_PATH, QEMU_CAPS_OBJECT_MEMORY_RAM,
             QEMU_CAPS_OBJECT_MEMORY_FILE);
+    DO_TEST_FAILURE("hugepages-pages4", QEMU_CAPS_MEM_PATH,
+            QEMU_CAPS_OBJECT_MEMORY_RAM, QEMU_CAPS_OBJECT_MEMORY_FILE);
     DO_TEST("nosharepages", QEMU_CAPS_MACHINE_OPT, QEMU_CAPS_MEM_MERGE);
     DO_TEST("disk-cdrom", NONE);
     DO_TEST("disk-cdrom-network-http", QEMU_CAPS_KVM, QEMU_CAPS_DEVICE,