[Xen-devel] [PATCH] xl: fix sedf parameters checking

[Dario Faggioli <raistlin@xxxxxxxx>]

9d1fd58ff602 was bogous 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@xxxxxxxxxxxxx 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@xxxxxxxxx>

diff --git a/tools/libxl/xl_cmdimpl.c b/tools/libxl/xl_cmdimpl.c
--- a/tools/libxl/xl_cmdimpl.c
+++ b/tools/libxl/xl_cmdimpl.c
@@ -555,6 +555,8 @@ static int sched_params_valid(libxl_doma
     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_doma
     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;
     }
 

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