libxl: implement virDomainGetNumaParameters

Although, having it depending on Xen >= 4.3 (by using the proper
libxl feature flag).

Xen currently implements a NUMA placement policy which is basically
the same as the 'interleaved' policy of `numactl', although it can
be applied on a subset of the available nodes. We therefore hardcode
"interleave" as 'numa_mode', and we use the newly introduced libxl
interface to figure out what nodes a domain spans ('numa_nodeset').

With this change, it is now possible to query the NUMA node
affinity of a running domain:

[raistlin@Zhaman ~]$ sudo virsh --connect xen:/// list
 Id    Name                           State
----------------------------------------------------
 23    F18_x64                        running

[raistlin@Zhaman ~]$ sudo virsh --connect xen:/// numatune 23
numa_mode      : interleave
numa_nodeset   : 1
Signed-off-by: NDario Faggioli <dario.faggioli@citrix.com>

src/libxl/libxl_driver.c

@@ -28,6 +28,7 @@
 
 #include <math.h>
 #include <libxl.h>
+#include <libxl_utils.h>
 #include <fcntl.h>
 #include <regex.h>
 
@@ -4499,6 +4500,143 @@ libxlDomainSetSchedulerParameters(virDomainPtr dom, virTypedParameterPtr params,
     return libxlDomainSetSchedulerParametersFlags(dom, params, nparams, 0);
 }
 
+/* NUMA node affinity information is available through libxl
+ * starting from Xen 4.3. */
+#ifdef LIBXL_HAVE_DOMAIN_NODEAFFINITY
+
+/* Number of Xen NUMA parameters */
+# define LIBXL_NUMA_NPARAM 2
+
+static int
+libxlDomainGetNumaParameters(virDomainPtr dom,
+                             virTypedParameterPtr params,
+                             int *nparams,
+                             unsigned int flags)
+{
+    libxlDriverPrivatePtr driver = dom->conn->privateData;
+    libxlDomainObjPrivatePtr priv;
+    virDomainObjPtr vm;
+    libxl_bitmap nodemap;
+    virBitmapPtr nodes = NULL;
+    char *nodeset = NULL;
+    int rc, ret = -1;
+    size_t i, j;
+
+    /* In Xen 4.3, it is possible to query the NUMA node affinity of a domain
+     * via libxl, but not to change it. We therefore only allow AFFECT_LIVE. */
+    virCheckFlags(VIR_DOMAIN_AFFECT_LIVE |
+                  VIR_TYPED_PARAM_STRING_OKAY, -1);
+
+    /* We blindly return a string, and let libvirt.c and remote_driver.c do
+     * the filtering on behalf of older clients that can't parse it. */
+    flags &= ~VIR_TYPED_PARAM_STRING_OKAY;
+
+    libxlDriverLock(driver);
+    vm = virDomainObjListFindByUUID(driver->domains, dom->uuid);
+    libxlDriverUnlock(driver);
+
+    if (!vm) {
+        virReportError(VIR_ERR_NO_DOMAIN, "%s",
+                       _("no domain with matching uuid"));
+        goto cleanup;
+    }
+
+    if (virDomainGetNumaParametersEnsureACL(dom->conn, vm->def) < 0)
+        goto cleanup;
+
+    if (!virDomainObjIsActive(vm)) {
+        virReportError(VIR_ERR_OPERATION_INVALID, "%s",
+                       _("Domain is not running"));
+        goto cleanup;
+    }
+
+    priv = vm->privateData;
+
+    libxl_bitmap_init(&nodemap);
+
+    if ((*nparams) == 0) {
+        *nparams = LIBXL_NUMA_NPARAM;
+        ret = 0;
+        goto cleanup;
+    }
+
+    for (i = 0; i < LIBXL_NUMA_NPARAM && i < *nparams; i++) {
+        virMemoryParameterPtr param = &params[i];
+
+        switch (i) {
+        case 0:
+            /* NUMA mode */
+
+            /* Xen implements something that is really close to numactl's
+             * 'interleave' policy (see `man 8 numactl' for details). */
+            if (virTypedParameterAssign(param, VIR_DOMAIN_NUMA_MODE,
+                                        VIR_TYPED_PARAM_INT,
+                                        VIR_DOMAIN_NUMATUNE_MEM_INTERLEAVE) < 0)
+                goto cleanup;
+
+            break;
+
+        case 1:
+            /* Node affinity */
+
+            /* Let's allocate both libxl and libvirt bitmaps */
+            if (libxl_node_bitmap_alloc(priv->ctx, &nodemap, 0) ||
+                !(nodes = virBitmapNew(libxl_get_max_nodes(priv->ctx)))) {
+                virReportOOMError();
+                goto cleanup;
+            }
+
+            rc = libxl_domain_get_nodeaffinity(priv->ctx,
+                                               vm->def->id,
+                                               &nodemap);
+            if (rc != 0) {
+                virReportSystemError(-rc, "%s",
+                                     _("unable to get numa affinity"));
+                goto cleanup;
+            }
+
+            /* First, we convert libxl_bitmap into virBitmap. After that,
+             * we format virBitmap as a string that can be returned. */
+            virBitmapClearAll(nodes);
+            libxl_for_each_set_bit(j, nodemap) {
+                if (virBitmapSetBit(nodes, j)) {
+                    virReportError(VIR_ERR_INTERNAL_ERROR,
+                                   _("Node %zu out of range"), j);
+                    goto cleanup;
+                }
+            }
+
+            nodeset = virBitmapFormat(nodes);
+            if (!nodeset && VIR_STRDUP(nodeset, "") < 0)
+                goto cleanup;
+
+            if (virTypedParameterAssign(param, VIR_DOMAIN_NUMA_NODESET,
+                                        VIR_TYPED_PARAM_STRING, nodeset) < 0)
+                goto cleanup;
+
+            nodeset = NULL;
+
+            break;
+
+        default:
+            break;
+        }
+    }
+
+    if (*nparams > LIBXL_NUMA_NPARAM)
+        *nparams = LIBXL_NUMA_NPARAM;
+    ret = 0;
+
+cleanup:
+    VIR_FREE(nodeset);
+    virBitmapFree(nodes);
+    libxl_bitmap_dispose(&nodemap);
+    if (vm)
+        virObjectUnlock(vm);
+    return ret;
+}
+#endif
+
 static int
 libxlDomainIsActive(virDomainPtr dom)
 {
@@ -4727,6 +4865,9 @@ static virDriver libxlDriver = {
     .domainGetSchedulerParametersFlags = libxlDomainGetSchedulerParametersFlags, /* 0.9.2 */
     .domainSetSchedulerParameters = libxlDomainSetSchedulerParameters, /* 0.9.0 */
     .domainSetSchedulerParametersFlags = libxlDomainSetSchedulerParametersFlags, /* 0.9.2 */
+#ifdef LIBXL_HAVE_DOMAIN_NODEAFFINITY
+    .domainGetNumaParameters = libxlDomainGetNumaParameters, /* 1.1.1 */
+#endif
     .nodeGetFreeMemory = libxlNodeGetFreeMemory, /* 0.9.0 */
     .nodeGetCellsFreeMemory = libxlNodeGetCellsFreeMemory, /* 1.1.1 */
     .connectDomainEventRegister = libxlConnectDomainEventRegister, /* 0.9.0 */