qemuDomainAttachMemory: Crate hugepage dir if needed

https://bugzilla.redhat.com/show_bug.cgi?id=1455819

It may happen that a domain is started without any huge pages.
However, user might try to attach a DIMM module later. DIMM
backed by huge pages (why would somebody want to mix regular and
huge pages is beyond me). Therefore we have to create the dir if
we haven't done so far.
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>
Reviewed-by: NJohn Ferlan <jferlan@redhat.com>

src/qemu/qemu_hotplug.c

@@ -2258,6 +2258,9 @@ qemuDomainAttachMemory(virQEMUDriverPtr driver,
                                   priv->qemuCaps, vm->def, mem, NULL, true) < 0)
         goto cleanup;
 
+    if (qemuProcessBuildDestroyHugepagesPath(driver, vm, mem, true) < 0)
+        goto cleanup;
+
     if (qemuDomainNamespaceSetupMemory(driver, vm, mem) < 0)
         goto cleanup;
     teardowndevice = true;

src/qemu/qemu_process.c

@@ -3284,7 +3284,8 @@ qemuProcessReconnectCheckMemAliasOrderMismatch(virDomainObjPtr vm)
 
 
 static bool
-qemuProcessNeedHugepagesPath(virDomainDefPtr def)
+qemuProcessNeedHugepagesPath(virDomainDefPtr def,
+                             virDomainMemoryDefPtr mem)
 {
     const long system_pagesize = virGetSystemPageSizeKB();
     size_t i;
@@ -3304,13 +3305,20 @@ qemuProcessNeedHugepagesPath(virDomainDefPtr def)
             return true;
     }
 
+    if (mem &&
+        mem->model == VIR_DOMAIN_MEMORY_MODEL_DIMM &&
+        mem->pagesize &&
+        mem->pagesize != system_pagesize)
+        return true;
+
     return false;
 }
 
 
-static int
+int
 qemuProcessBuildDestroyHugepagesPath(virQEMUDriverPtr driver,
                                      virDomainObjPtr vm,
+                                     virDomainMemoryDefPtr mem,
                                      bool build)
 {
     virQEMUDriverConfigPtr cfg = virQEMUDriverGetConfig(driver);
@@ -3320,7 +3328,7 @@ qemuProcessBuildDestroyHugepagesPath(virQEMUDriverPtr driver,
     int ret = -1;
 
     if (build)
-        shouldBuild = qemuProcessNeedHugepagesPath(vm->def);
+        shouldBuild = qemuProcessNeedHugepagesPath(vm->def, mem);
 
     if (!build || shouldBuild) {
         for (i = 0; i < cfg->nhugetlbfs; i++) {
@@ -3331,6 +3339,11 @@ qemuProcessBuildDestroyHugepagesPath(virQEMUDriverPtr driver,
                 goto cleanup;
 
             if (build) {
+                if (virFileExists(hugepagePath)) {
+                    ret = 0;
+                    goto cleanup;
+                }
+
                 if (virFileMakePathWithMode(hugepagePath, 0700) < 0) {
                     virReportSystemError(errno,
                                          _("Unable to create %s"),
@@ -3504,7 +3517,7 @@ qemuProcessReconnect(void *opaque)
         goto cleanup;
     }
 
-    if (qemuProcessBuildDestroyHugepagesPath(driver, obj, true) < 0)
+    if (qemuProcessBuildDestroyHugepagesPath(driver, obj, NULL, true) < 0)
         goto error;
 
     if ((qemuDomainAssignAddresses(obj->def, priv->qemuCaps,
@@ -5572,7 +5585,7 @@ qemuProcessPrepareHost(virQEMUDriverPtr driver,
                                NULL) < 0)
         goto cleanup;
 
-    if (qemuProcessBuildDestroyHugepagesPath(driver, vm, true) < 0)
+    if (qemuProcessBuildDestroyHugepagesPath(driver, vm, NULL, true) < 0)
         goto cleanup;
 
     /* Ensure no historical cgroup for this VM is lying around bogus
@@ -6259,7 +6272,7 @@ void qemuProcessStop(virQEMUDriverPtr driver,
         goto endjob;
     }
 
-    qemuProcessBuildDestroyHugepagesPath(driver, vm, false);
+    qemuProcessBuildDestroyHugepagesPath(driver, vm, NULL, false);
 
     vm->def->id = -1;
 

src/qemu/qemu_process.h

@@ -38,6 +38,11 @@ int qemuProcessStopCPUs(virQEMUDriverPtr driver,
                         virDomainPausedReason reason,
                         qemuDomainAsyncJob asyncJob);
 
+int qemuProcessBuildDestroyHugepagesPath(virQEMUDriverPtr driver,
+                                         virDomainObjPtr vm,
+                                         virDomainMemoryDefPtr mem,
+                                         bool build);
+
 void qemuProcessAutostartAll(virQEMUDriverPtr driver);
 void qemuProcessReconnectAll(virConnectPtr conn, virQEMUDriverPtr driver);