[libvirt] [PATCH v2] libxl: libxl_get_max_cpus returning a libxl error from 4.4 onward

[Dario Faggioli]

Starting from commit 2e82c18c in Xen (will be included in Xen 4.4)
both libxl_get_max_cpus() and libxl_get_max_ndoes() start returning
a proper libxl error code, in case of failure. This patch fixes
this in the libxl driver.

Note that, although it is now basically impossible for them to return
0, that would, theoretically, still be wrong. Also, checking that the
returned value is '<= 0' makes the code correct for both Xen 4.4 and
Xen 4.3 (and 4.2), and that is why we go for it (rather than
just '< 0').

Signed-off-by: Dario Faggioli <dario.faggioli at citrix.com>
Cc: Jim Fehlig <jfehlig at suse.com>
Cc: Ian Jackson <Ian.Jackson at eu.citrix.com>
Cc: Martin Kletzander <mkletzan at redhat.com>
---
Changes from v1:
 * taking care of libxl_get_max_nodes() too
---
 src/libxl/libxl_driver.c |   15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/src/libxl/libxl_driver.c b/src/libxl/libxl_driver.c
index 692c3b7..29aa6c7 100644
--- a/src/libxl/libxl_driver.c
+++ b/src/libxl/libxl_driver.c
@@ -1101,9 +1101,11 @@ libxlConnectGetMaxVcpus(virConnectPtr conn, const char *type ATTRIBUTE_UNUSED)
 
     cfg = libxlDriverConfigGet(driver);
     ret = libxl_get_max_cpus(cfg->ctx);
-    /* libxl_get_max_cpus() will return 0 if there were any failures,
-       e.g. xc_physinfo() failing */
-    if (ret == 0)
+    /* On failure, libxl_get_max_cpus() will return ERROR_FAIL from Xen 4.4
+     * onward, but it ever returning 0 is obviously wrong too (and it is
+     * what happens, on failure, on Xen 4.3 and earlier). Therefore, a 'less
+     * or equal' is the catchall we want. */
+    if (ret <= 0)
         ret = -1;
 
     virObjectUnref(cfg);
@@ -3980,6 +3982,7 @@ libxlDomainGetNumaParameters(virDomainPtr dom,
 
     for (i = 0; i < LIBXL_NUMA_NPARAM && i < *nparams; i++) {
         virMemoryParameterPtr param = &params[i];
+        int numnodes;
 
         switch (i) {
         case 0:
@@ -3998,8 +4001,12 @@ libxlDomainGetNumaParameters(virDomainPtr dom,
             /* Node affinity */
 
             /* Let's allocate both libxl and libvirt bitmaps */
+            numnodes = libxl_get_max_nodes(priv->ctx);
+            if (numnodes <= 0)
+                goto cleanup;
+
             if (libxl_node_bitmap_alloc(priv->ctx, &nodemap, 0) ||
-                !(nodes = virBitmapNew(libxl_get_max_nodes(priv->ctx)))) {
+                !(nodes = virBitmapNew(numnodes))) {
                 virReportOOMError();
                 goto cleanup;
             }