[PATCH] xl: check for meaningful combination of sedf config file parameters

[Dario Faggioli <raistlin@linux.it>]

As we do it in the implementation of `xl sched-sedf -d ...', some
consistency checking is needed while parsing the sedf scheduling
parameters provided via config file. Not doing this results in the call
libxl_domain_sched_params_set() to fail, and no parameters being
enforced for the domain.

Note we do this at config file parsing time as that gives us the chance
of bailing out early. It would have been pointless to add it within
sched_sedf_domain_set() (in libxl), as the very same thing is
done in the hypervisor, and the result is being checked and returned
to the caller already.

Signed-off-by: Dario Faggioli <dario.faggioli@citrix.com>

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
@@ -561,6 +561,7 @@ static void parse_config_data(const char
     long l;
     XLU_Config *config;
     XLU_ConfigList *cpus, *vbds, *nics, *pcis, *cvfbs, *cpuids;
+    int opt_w = 0, opt_p = 0, opt_s = 0;
     int pci_power_mgmt = 0;
     int pci_msitranslate = 1;
     int pci_permissive = 0;
@@ -632,18 +633,36 @@ static void parse_config_data(const char
 
     /* the following is the actual config parsing with overriding
      * values in the structures */
-    if (!xlu_cfg_get_long (config, "cpu_weight", &l, 0))
+    if (!xlu_cfg_get_long (config, "cpu_weight", &l, 0)) {
         b_info->sched_params.weight = l;
+        opt_w = 1;
+    }
     if (!xlu_cfg_get_long (config, "cap", &l, 0))
         b_info->sched_params.cap = l;
-    if (!xlu_cfg_get_long (config, "period", &l, 0))
+    if (!xlu_cfg_get_long (config, "period", &l, 0)) {
         b_info->sched_params.period = l;
-    if (!xlu_cfg_get_long (config, "slice", &l, 0))
+        opt_p = 1;
+    }
+    if (!xlu_cfg_get_long (config, "slice", &l, 0)) {
         b_info->sched_params.slice = l;
+        opt_s = 1;
+    }
     if (!xlu_cfg_get_long (config, "latency", &l, 0))
         b_info->sched_params.latency = l;
     if (!xlu_cfg_get_long (config, "extratime", &l, 0))
         b_info->sched_params.extratime = l;
+    /* The sedf scheduler needs some more consistency checking */
+    if (opt_w && (opt_p || opt_s)) {
+        fprintf(stderr, "Either specify a weight OR a period and slice\n");
+        exit(1);
+    }
+    if (opt_w) {
+        b_info->sched_params.slice = 0;
+        b_info->sched_params.period = 0;
+    }
+    if (opt_p || opt_s)
+        b_info->sched_params.weight = 0;
+
 
     if (!xlu_cfg_get_long (config, "vcpus", &l, 0)) {
         b_info->max_vcpus = l;