[Xen-devel] [PATCH 1/2] libxl: turn NUMA placement misconfigs into warnings

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

instead than errors. More specifically, in libxl,
b_info->numa_autoplacement is meant as a way to
disable automatic NUMA placement, if one does not
want it to happen. It is, however, useful for
consistency checking as well, i.e., to ensure that
the user provided configuration (such as, for instance,
vcpu hard or soft affinity) and NUMA placement itself
will not clash.

However, right now, if such a clash happens we abort
domain creation and error out, which is too much! It
is, in fact, enough to infom the user/caller that NUMA
placement won't be performed, with a WARN, and that's
what this commit does.

Signed-off-by: Dario Faggioli <dario.faggioli@xxxxxxxxxx>
---
Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
Cc: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
Cc: Ian Campbell <ian.campbell@xxxxxxxxxx>
Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
---
 tools/libxl/libxl_dom.c |   76 +++++++++++++++++++++++------------------------
 1 file changed, 37 insertions(+), 39 deletions(-)

diff --git a/tools/libxl/libxl_dom.c b/tools/libxl/libxl_dom.c
index 1c9418a..b9a77a5 100644
--- a/tools/libxl/libxl_dom.c
+++ b/tools/libxl/libxl_dom.c
@@ -330,50 +330,48 @@ int libxl__build_pre(libxl__gc *gc, uint32_t domid,
      * reflect the placement result if that is the case
      */
     if (libxl_defbool_val(info->numa_placement)) {
-        libxl_bitmap cpumap_soft;
-
-        if (info->cpumap.size ||
-            info->num_vcpu_hard_affinity || info->num_vcpu_soft_affinity) {
-            LOG(ERROR, "Can run NUMA placement only if no vcpu "
-                       "(hard or soft) affinity is specified explicitly");
-            return ERROR_INVAL;
-        }
-        if (info->nodemap.size) {
-            LOG(ERROR, "Can run NUMA placement only if the domain does not "
-                       "have any NUMA node affinity set already");
-            return ERROR_INVAL;
-        }
-
-        rc = libxl_node_bitmap_alloc(ctx, &info->nodemap, 0);
-        if (rc)
-            return rc;
-        libxl_bitmap_set_any(&info->nodemap);
+        if (info->cpumap.size || info->num_vcpu_hard_affinity ||
+            info->num_vcpu_soft_affinity)
+            LOG(WARN, "Can't run NUMA placement, as an (hard or soft) "
+                      "affinity has been specified explicitly");
+        else if (info->nodemap.size)
+            LOG(WARN, "Can't run NUMA placement, as the domain has "
+                      "NUMA node affinity set already");
+        else {
+            libxl_bitmap cpumap_soft;
+
+            rc = libxl_node_bitmap_alloc(ctx, &info->nodemap, 0);
+            if (rc)
+                return rc;
+            libxl_bitmap_set_any(&info->nodemap);
+
+            rc = libxl_cpu_bitmap_alloc(ctx, &cpumap_soft, 0);
+            if (rc)
+                return rc;
+
+            rc = numa_place_domain(gc, domid, info);
+            if (rc) {
+                libxl_bitmap_dispose(&cpumap_soft);
+                return rc;
+            }
 
-        rc = libxl_cpu_bitmap_alloc(ctx, &cpumap_soft, 0);
-        if (rc)
-            return rc;
+            /*
+             * All we need to do now is converting the result of automatic
+             * placement from nodemap to cpumap, and then use such cpumap
+             * as the soft affinity for all the vcpus of the domain.
+             *
+             * When calling libxl_set_vcpuaffinity_all(), it is ok to use
+             * NULL as hard affinity, as we know we don't have one, or we
+             * won't be here.
+             */
+            libxl_nodemap_to_cpumap(ctx, &info->nodemap, &cpumap_soft);
+            libxl_set_vcpuaffinity_all(ctx, domid, info->max_vcpus,
+                                       NULL, &cpumap_soft);
 
-        rc = numa_place_domain(gc, domid, info);
-        if (rc) {
             libxl_bitmap_dispose(&cpumap_soft);
-            return rc;
         }
-
-        /*
-         * All we need to do now is converting the result of automatic
-         * placement from nodemap to cpumap, and then use such cpumap as
-         * the soft affinity for all the vcpus of the domain.
-         *
-         * When calling libxl_set_vcpuaffinity_all(), it is ok to use NULL
-         * as hard affinity, as we know we don't have one, or we won't be
-         * here.
-         */
-        libxl_nodemap_to_cpumap(ctx, &info->nodemap, &cpumap_soft);
-        libxl_set_vcpuaffinity_all(ctx, domid, info->max_vcpus,
-                                   NULL, &cpumap_soft);
-
-        libxl_bitmap_dispose(&cpumap_soft);
     }
+
     if (info->nodemap.size)
         libxl_domain_set_nodeaffinity(ctx, domid, &info->nodemap);
 


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