xl: fix sedf parameters checking

25468:9d1fd58ff602 was bogus in not letting a new domain being created
if its scheduling parameters --when running under the sedf scheduler--
were not fully specified, making creation fail like in this example
here below:

2012-06-16 07:37:47 Z executing ssh ... root@10.80.248.105 xl create /etc/xen/debian.guest.osstest.cfg
libxl: error: libxl.c:3619:sched_sedf_domain_set: setting domain sched sedf: Invalid argument
libxl: error: libxl_create.c:710:domcreate_bootloader_done: cannot (re-)build domain: -3
Parsing config from /etc/xen/debian.guest.osstest.cfg

This is due to the fact the values for period, slice, weight and
extratime should be consistent among each others, and if not all
are explicitly specified, someone has to make that happen. That
was right the purpose of the change in question, but it was failing
at achieving so.

This commit fixes things by forcing unspecified parameters to
sensible values, depending on the ones the user provided.

Signed-off-by: Dario Faggioli <dario.faggioli@citix.com>
Committed-by: Ian Jackson <ian.jackson@eu.citrix.com>

diff --git a/tools/libxl/xl_cmdimpl.c b/tools/libxl/xl_cmdimpl.c
index 3ea95ef4267485e41033f6a5c6a75cd33d8dcb9c..63dc564cb28f733a70aa8287a6e8a94de5ce8a8b 100644 (file)
--- a/tools/libxl/xl_cmdimpl.c
+++ b/tools/libxl/xl_cmdimpl.c
@@ -555,6 +555,8 @@ static int sched_params_valid(libxl_domain_sched_params *scp)
     int has_weight = scp->weight != LIBXL_DOMAIN_SCHED_PARAM_WEIGHT_DEFAULT;
     int has_period = scp->period != LIBXL_DOMAIN_SCHED_PARAM_PERIOD_DEFAULT;
     int has_slice = scp->slice != LIBXL_DOMAIN_SCHED_PARAM_SLICE_DEFAULT;
+    int has_extratime =
+                scp->extratime != LIBXL_DOMAIN_SCHED_PARAM_EXTRATIME_DEFAULT;
     libxl_domain_sched_params sci;
 
     libxl_domain_sched_params_get(ctx, domid, &sci);
@@ -563,12 +565,27 @@ static int sched_params_valid(libxl_domain_sched_params *scp)
     if (sci.sched == LIBXL_SCHEDULER_SEDF) {
         if (has_weight && (has_period || has_slice))
             return 0;
+        if (has_period != has_slice)
+            return 0;
 
+        /*
+         * Idea is, if we specify a weight, then both period and
+         * slice has to be zero. OTOH, if we do not specify a weight,
+         * that means we want a pure best effort domain or an actual
+         * real-time one. In the former case, it is period that needs
+         * to be zero, in the latter, weight should be.
+         */
         if (has_weight) {
             scp->slice = 0;
             scp->period = 0;
         }
-        if (has_period || has_slice)
+        else if (!has_period) {
+            /* We can setup a proper best effort domain (extra time only)
+             * iff we either already have or are asking for some extra time. */
+            scp->weight = has_extratime ? scp->extratime : sci.extratime;
+            scp->period = 0;
+        }
+        if (has_period && has_slice)
             scp->weight = 0;
     }