[PATCH] xl, cpupools: Create empty pool if no cpus are specified

[George Dunlap <george.dunlap@eu.citrix.com>]

Currently, if "xl cpupool-create" is called with no cpus configured,
xl will choose a cpu at random from the list of unassigned cpus, and
if no unassigned cpus are available, it will fail.

This seems to me to be a poor interface.  For one, it makes it impossible
to create an empty cpupool using the xl command-line, except by creating
a pool and then removing the cpus from it.  For two, I don't think assigning
a random cpu is a feature; it's not unreasonable for the user to specify
which cpus to add to which pools.

This patch changes the behavior of "xl cpupool-create" to create an empty
pool if no cpus are specified.  I believe this interface to be more expected
and more script-friendly.

Signed-off-by: George Dunlap <george.dunlap@eu.citrix.com>

diff -r 7530af17cfcf -r c53f124c8c44 tools/libxl/xl_cmdimpl.c
--- a/tools/libxl/xl_cmdimpl.c	Thu Apr 05 14:04:53 2012 +0100
+++ b/tools/libxl/xl_cmdimpl.c	Thu Apr 05 14:14:32 2012 +0100
@@ -5734,20 +5734,8 @@ int main_cpupoolcreate(int argc, char **
             libxl_cpumap_set(&cpumap, i);
             n_cpus++;
         }
-    } else {
-        n_cpus = 1;
-        n = 0;
-        libxl_for_each_cpu(i, freemap)
-            if (libxl_cpumap_test(&freemap, i)) {
-                n++;
-                libxl_cpumap_set(&cpumap, i);
-                break;
-            }
-        if (n < n_cpus) {
-            fprintf(stderr, "no free cpu found\n");
-            return -ERROR_FAIL;
-        }
-    }
+    } else
+        n_cpus = 0;
 
     libxl_uuid_generate(&uuid);