tools: sched: add support for 'null' scheduler

From: Dario Faggioli <dario.faggioli@xxxxxxxxxx>

It being very very basic, also means this scheduler does
not need much support at the tools level (for now).

Basically, just the definition of the symbol of the
scheduler itself and a couple of stubs.

Signed-off-by: Dario Faggioli <dario.faggioli@xxxxxxxxxx>
Acked-by: Wei Liu <wei.liu2@xxxxxxxxxx>
Acked-by: Stefano Stabellini <stefano@xxxxxxxxxxx>
---
Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
Cc: George Dunlap <george.dunlap@xxxxxxxxxx>
Cc: Julien Grall <julien.grall@xxxxxxx>
---
 tools/libxl/libxl.h         |    6 ++++++
 tools/libxl/libxl_sched.c   |   24 ++++++++++++++++++++++++
 tools/libxl/libxl_types.idl |    1 +
 3 files changed, 31 insertions(+)

diff --git a/tools/libxl/libxl.h b/tools/libxl/libxl.h
index a402236..cf8687a 100644
--- a/tools/libxl/libxl.h
+++ b/tools/libxl/libxl.h
@@ -210,6 +210,12 @@
 #define LIBXL_HAVE_SCHED_RTDS 1
 
 /*
+ * LIBXL_HAVE_SCHED_NULL indicates that the 'null' static scheduler
+ * is available.
+ */
+#define LIBXL_HAVE_SCHED_NULL 1
+
+/*
  * libxl_domain_build_info has u.hvm.viridian_enable and _disable bitmaps
  * of the specified width.
  */
diff --git a/tools/libxl/libxl_sched.c b/tools/libxl/libxl_sched.c
index 84d3837..d763b9a 100644
--- a/tools/libxl/libxl_sched.c
+++ b/tools/libxl/libxl_sched.c
@@ -178,6 +178,20 @@ static int sched_arinc653_domain_set(libxl__gc *gc, uint32_t domid,
     return 0;
 }
 
+static int sched_null_domain_set(libxl__gc *gc, uint32_t domid,
+                                 const libxl_domain_sched_params *scinfo)
+{
+    /* There aren't any domain-specific parameters to be set. */
+    return 0;
+}
+
+static int sched_null_domain_get(libxl__gc *gc, uint32_t domid,
+                               libxl_domain_sched_params *scinfo)
+{
+    /* There aren't any domain-specific parameters to return. */
+    return 0;
+}
+
 static int sched_credit_domain_get(libxl__gc *gc, uint32_t domid,
                                    libxl_domain_sched_params *scinfo)
 {
@@ -730,6 +744,9 @@ int libxl_domain_sched_params_set(libxl_ctx *ctx, uint32_t domid,
     case LIBXL_SCHEDULER_RTDS:
         ret=sched_rtds_domain_set(gc, domid, scinfo);
         break;
+    case LIBXL_SCHEDULER_NULL:
+        ret=sched_null_domain_set(gc, domid, scinfo);
+        break;
     default:
         LOGD(ERROR, domid, "Unknown scheduler");
         ret=ERROR_INVAL;
@@ -758,6 +775,7 @@ int libxl_vcpu_sched_params_set(libxl_ctx *ctx, uint32_t domid,
     case LIBXL_SCHEDULER_CREDIT:
     case LIBXL_SCHEDULER_CREDIT2:
     case LIBXL_SCHEDULER_ARINC653:
+    case LIBXL_SCHEDULER_NULL:
         LOGD(ERROR, domid, "per-VCPU parameter setting not supported for this scheduler");
         rc = ERROR_INVAL;
         break;
@@ -792,6 +810,7 @@ int libxl_vcpu_sched_params_set_all(libxl_ctx *ctx, uint32_t domid,
     case LIBXL_SCHEDULER_CREDIT:
     case LIBXL_SCHEDULER_CREDIT2:
     case LIBXL_SCHEDULER_ARINC653:
+    case LIBXL_SCHEDULER_NULL:
         LOGD(ERROR, domid, "per-VCPU parameter setting not supported for this scheduler");
         rc = ERROR_INVAL;
         break;
@@ -832,6 +851,9 @@ int libxl_domain_sched_params_get(libxl_ctx *ctx, uint32_t domid,
     case LIBXL_SCHEDULER_RTDS:
         ret=sched_rtds_domain_get(gc, domid, scinfo);
         break;
+    case LIBXL_SCHEDULER_NULL:
+        ret=sched_null_domain_get(gc, domid, scinfo);
+        break;
     default:
         LOGD(ERROR, domid, "Unknown scheduler");
         ret=ERROR_INVAL;
@@ -858,6 +880,7 @@ int libxl_vcpu_sched_params_get(libxl_ctx *ctx, uint32_t domid,
     case LIBXL_SCHEDULER_CREDIT:
     case LIBXL_SCHEDULER_CREDIT2:
     case LIBXL_SCHEDULER_ARINC653:
+    case LIBXL_SCHEDULER_NULL:
         LOGD(ERROR, domid, "per-VCPU parameter getting not supported for this scheduler");
         rc = ERROR_INVAL;
         break;
@@ -890,6 +913,7 @@ int libxl_vcpu_sched_params_get_all(libxl_ctx *ctx, uint32_t domid,
     case LIBXL_SCHEDULER_CREDIT:
     case LIBXL_SCHEDULER_CREDIT2:
     case LIBXL_SCHEDULER_ARINC653:
+    case LIBXL_SCHEDULER_NULL:
         LOGD(ERROR, domid, "per-VCPU parameter getting not supported for this scheduler");
         rc = ERROR_INVAL;
         break;
diff --git a/tools/libxl/libxl_types.idl b/tools/libxl/libxl_types.idl
index d970284..d42f6a1 100644
--- a/tools/libxl/libxl_types.idl
+++ b/tools/libxl/libxl_types.idl
@@ -191,6 +191,7 @@ libxl_scheduler = Enumeration("scheduler", [
     (6, "credit2"),
     (7, "arinc653"),
     (8, "rtds"),
+    (9, "null"),
     ])
 
 # Consistent with SHUTDOWN_* in sched.h (apart from UNKNOWN)