[libvirt] [PATCH] conf/qemu: enforce NUMA nodes only for x86 memory hotplug

[Nikunj A Dadhania]

libvirt enforces at least one NUMA node for memory hotplug support on
all architectures. While it might be required for some x86 guest,
PowerPC can hotplug memory on non-NUMA system.

The generic checks are replaced with arch specific check and xml
validation too does not enforce "node" for non-x86 arch.

CC: Peter Krempa <pkrempa at redhat.com>
Signed-off-by: Nikunj A Dadhania <nikunj at linux.vnet.ibm.com>
---
 src/conf/domain_conf.c  |  9 ++++++---
 src/qemu/qemu_command.c | 28 +++++++++++++++++-----------
 2 files changed, 23 insertions(+), 14 deletions(-)

diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index fd0450f..4cb2d4a 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -12430,6 +12430,7 @@ virDomainMemorySourceDefParseXML(xmlNodePtr node,
 
 static int
 virDomainMemoryTargetDefParseXML(xmlNodePtr node,
+                                 const virDomainDef *domDef,
                                  xmlXPathContextPtr ctxt,
                                  virDomainMemoryDefPtr def)
 {
@@ -12437,7 +12438,7 @@ virDomainMemoryTargetDefParseXML(xmlNodePtr node,
     xmlNodePtr save = ctxt->node;
     ctxt->node = node;
 
-    if (virXPathUInt("string(./node)", ctxt, &def->targetNode) < 0) {
+    if (virXPathUInt("string(./node)", ctxt, &def->targetNode) < 0 && ARCH_IS_X86(domDef->os.arch)) {
         virReportError(VIR_ERR_XML_ERROR, "%s",
                        _("invalid or missing value of memory device node"));
         goto cleanup;
@@ -12457,6 +12458,7 @@ virDomainMemoryTargetDefParseXML(xmlNodePtr node,
 
 static virDomainMemoryDefPtr
 virDomainMemoryDefParseXML(xmlNodePtr memdevNode,
+                           const virDomainDef *domDef,
                            xmlXPathContextPtr ctxt,
                            unsigned int flags)
 {
@@ -12495,7 +12497,7 @@ virDomainMemoryDefParseXML(xmlNodePtr memdevNode,
         goto error;
     }
 
-    if (virDomainMemoryTargetDefParseXML(node, ctxt, def) < 0)
+    if (virDomainMemoryTargetDefParseXML(node, domDef, ctxt, def) < 0)
         goto error;
 
     if (virDomainDeviceInfoParseXML(memdevNode, NULL, &def->info, flags) < 0)
@@ -12647,7 +12649,7 @@ virDomainDeviceDefParse(const char *xmlStr,
             goto error;
         break;
     case VIR_DOMAIN_DEVICE_MEMORY:
-        if (!(dev->data.memory = virDomainMemoryDefParseXML(node, ctxt, flags)))
+        if (!(dev->data.memory = virDomainMemoryDefParseXML(node, def, ctxt, flags)))
             goto error;
         break;
     case VIR_DOMAIN_DEVICE_NONE:
@@ -16328,6 +16330,7 @@ virDomainDefParseXML(xmlDocPtr xml,
 
     for (i = 0; i < n; i++) {
         virDomainMemoryDefPtr mem = virDomainMemoryDefParseXML(nodes[i],
+                                                               def,
                                                                ctxt,
                                                                flags);
         if (!mem)
diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index ae03618..51160e7 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -4979,8 +4979,12 @@ qemuBuildMemoryBackendStr(unsigned long long size,
     *backendProps = NULL;
     *backendType = NULL;
 
-    /* memory devices could provide a invalid guest node */
-    if (guestNode >= virDomainNumaGetNodeCount(def->numa)) {
+    /* memory devices could provide a invalid guest node. Moreover,
+     * x86 guests needs at least one numa node to support memory
+     * hotplug
+     */
+    if ((virDomainNumaGetNodeCount(def->numa) == 0 && ARCH_IS_X86(def->os.arch)) ||
+        guestNode > virDomainNumaGetNodeCount(def->numa)) {
         virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
                        _("can't add memory backend for guest node '%d' as "
                          "the guest has only '%zu' NUMA nodes configured"),
@@ -4991,10 +4995,12 @@ qemuBuildMemoryBackendStr(unsigned long long size,
     if (!(props = virJSONValueNewObject()))
         return -1;
 
-    memAccess = virDomainNumaGetNodeMemoryAccessMode(def->numa, guestNode);
-    if (virDomainNumatuneGetMode(def->numa, guestNode, &mode) < 0 &&
-        virDomainNumatuneGetMode(def->numa, -1, &mode) < 0)
-        mode = VIR_DOMAIN_NUMATUNE_MEM_STRICT;
+    if (virDomainNumaGetNodeCount(def->numa)) {
+        memAccess = virDomainNumaGetNodeMemoryAccessMode(def->numa, guestNode);
+        if (virDomainNumatuneGetMode(def->numa, guestNode, &mode) < 0 &&
+            virDomainNumatuneGetMode(def->numa, -1, &mode) < 0)
+            mode = VIR_DOMAIN_NUMATUNE_MEM_STRICT;
+    }
 
     if (pagesize == 0) {
         /* Find the huge page size we want to use */
@@ -9238,11 +9244,11 @@ qemuBuildCommandLine(virConnectPtr conn,
             goto error;
         }
 
-        /* due to guest support, qemu would silently enable NUMA with one node
-         * once the memory hotplug backend is enabled. To avoid possible
-         * confusion we will enforce user originated numa configuration along
-         * with memory hotplug. */
-        if (virDomainNumaGetNodeCount(def->numa) == 0) {
+        /* x86 windows guest needs at least one numa node to be
+         * present. While its not possible to detect what guest os is
+         * running, enforce this limitation only to x86 architecture.
+         */
+        if (ARCH_IS_X86(def->os.arch) && virDomainNumaGetNodeCount(def->numa) == 0) {
             virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
                            _("At least one numa node has to be configured when "
                              "enabling memory hotplug"));
-- 
2.4.3