libxl: set vcpu affinity during domain creation

Since Xen 4.5 libxl allows to set affinities during domain creation.
This enables Xen to allocate the domain memory on NUMA systems close to
the specified pcpus.

Libvirt can now handle <domain/cputune/vcpupin> in domU.xml correctly.

Without this change, Xen will create the domU and assign NUMA memory and
vcpu affinities on its own. Later libvirt will adjust the affinity,
which may move the vcpus away from the assigned NUMA node.

Signed-off-by: Olaf Hering <olaf@aepfle.de>
Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Reviewed-by: Jim Fehlig <jfehlig@suse.com>

src/libxl/libxl_conf.c

@@ -284,6 +284,56 @@ libxlMakeChrdevStr(virDomainChrDef *def, char **buf)
     return 0;
 }
 
+static int
+libxlSetVcpuAffinities(virDomainDef *def,
+                       libxl_ctx *ctx,
+                       libxl_domain_build_info *b_info)
+{
+    libxl_bitmap *vcpu_affinity_array;
+    unsigned int vcpuid;
+    unsigned int vcpu_idx = 0;
+    virDomainVcpuDef *vcpu;
+    bool has_vcpu_pin = false;
+
+    /* Get highest vcpuid with cpumask */
+    for (vcpuid = 0; vcpuid < b_info->max_vcpus; vcpuid++) {
+        vcpu = virDomainDefGetVcpu(def, vcpuid);
+        if (!vcpu)
+            continue;
+        if (!vcpu->cpumask)
+            continue;
+        vcpu_idx = vcpuid;
+        has_vcpu_pin = true;
+    }
+    /* Nothing to do */
+    if (!has_vcpu_pin)
+        return 0;
+
+    /* Adjust index */
+    vcpu_idx++;
+
+    b_info->num_vcpu_hard_affinity = vcpu_idx;
+    /* Will be released by libxl_domain_config_dispose */
+    b_info->vcpu_hard_affinity = g_new0(libxl_bitmap, vcpu_idx);
+    vcpu_affinity_array = b_info->vcpu_hard_affinity;
+
+    for (vcpuid = 0; vcpuid < vcpu_idx; vcpuid++) {
+        libxl_bitmap *map = &vcpu_affinity_array[vcpuid];
+        libxl_bitmap_init(map);
+        /* libxl owns the bitmap */
+        if (libxl_cpu_bitmap_alloc(ctx, map, 0))
+            return -1;
+        vcpu = virDomainDefGetVcpu(def, vcpuid);
+        /* Apply the given mask, or allow unhandled vcpus to run anywhere */
+        if (vcpu && vcpu->cpumask)
+            virBitmapToDataBuf(vcpu->cpumask, map->map, map->size);
+        else
+            libxl_bitmap_set_any(map);
+    }
+    libxl_defbool_set(&b_info->numa_placement, false);
+    return 0;
+}
+
 static int
 libxlMakeDomBuildInfo(virDomainDef *def,
                       libxlDriverConfig *cfg,
@@ -321,6 +371,9 @@ libxlMakeDomBuildInfo(virDomainDef *def,
     for (i = 0; i < virDomainDefGetVcpus(def); i++)
         libxl_bitmap_set((&b_info->avail_vcpus), i);
 
+    if (libxlSetVcpuAffinities(def, ctx, b_info))
+        return -1;
+
     switch ((virDomainClockOffsetType) clock.offset) {
     case VIR_DOMAIN_CLOCK_OFFSET_VARIABLE:
         if (clock.data.variable.basis == VIR_DOMAIN_CLOCK_BASIS_LOCALTIME)

src/libxl/libxl_domain.c

@@ -967,49 +967,6 @@ libxlDomainAutoCoreDump(libxlDriverPrivate *driver,
     return 0;
 }
 
-int
-libxlDomainSetVcpuAffinities(libxlDriverPrivate *driver, virDomainObj *vm)
-{
-    g_autoptr(libxlDriverConfig) cfg = libxlDriverConfigGet(driver);
-    virDomainVcpuDef *vcpu;
-    libxl_bitmap map;
-    virBitmap *cpumask = NULL;
-    size_t i;
-    int ret = -1;
-
-    libxl_bitmap_init(&map);
-
-    for (i = 0; i < virDomainDefGetVcpus(vm->def); ++i) {
-        vcpu = virDomainDefGetVcpu(vm->def, i);
-
-        if (!vcpu->online)
-            continue;
-
-        if (!(cpumask = vcpu->cpumask))
-            cpumask = vm->def->cpumask;
-
-        if (!cpumask)
-            continue;
-
-        if (virBitmapToData(cpumask, &map.map, (int *)&map.size) < 0)
-            goto cleanup;
-
-        if (libxl_set_vcpuaffinity(cfg->ctx, vm->def->id, i, &map, NULL) != 0) {
-            virReportError(VIR_ERR_INTERNAL_ERROR,
-                           _("Failed to pin vcpu '%zu' with libxenlight"), i);
-            goto cleanup;
-        }
-
-        libxl_bitmap_dispose(&map); /* Also returns to freshly-init'd state */
-    }
-
-    ret = 0;
-
- cleanup:
-    libxl_bitmap_dispose(&map);
-    return ret;
-}
-
 static int
 libxlDomainFreeMem(libxl_ctx *ctx, libxl_domain_config *d_config)
 {
@@ -1460,9 +1417,6 @@ libxlDomainStart(libxlDriverPrivate *driver,
         goto destroy_dom;
     }
 
-    if (libxlDomainSetVcpuAffinities(driver, vm) < 0)
-        goto destroy_dom;
-
     if (!start_paused) {
         libxlDomainUnpauseWrapper(cfg->ctx, domid);
         virDomainObjSetState(vm, VIR_DOMAIN_RUNNING, VIR_DOMAIN_RUNNING_BOOTED);

src/libxl/libxl_domain.h

@@ -124,10 +124,6 @@ int
 libxlDomainAutoCoreDump(libxlDriverPrivate *driver,
                         virDomainObj *vm);
 
-int
-libxlDomainSetVcpuAffinities(libxlDriverPrivate *driver,
-                             virDomainObj *vm);
-
 int
 libxlDomainStartNew(libxlDriverPrivate *driver,
                     virDomainObj *vm,