config-linux: add Intel RDT CLOS name sharing support

Creating a dedicated RDT Class of Service (CLOS) for each running
container, even they have exactly same Scheam, will lead to short of
CLOS, since there is a hardware limit for the number of CLOS, around
16 CLOS per platform.

This PR add one parameter 'closID' into existed spec to allow user
to specify which RDT Class of Service (CLOS) the container will be
located. So it can place these containers with same Schema into one
single CLOS.

Example:

"linux": {
    "intelRdt": {
        "closID": "guaranteed_group",
        "l3CacheSchema": "L3:0=ffff0;1=3ff"
    }
}

Signed-off-by: Lin Yang <lin.a.yang@intel.com>

config-linux.md

@@ -488,17 +488,20 @@ You MUST specify at least one of the `hcaHandles` or `hcaObjects` in a given ent
 ## <a name="configLinuxIntelRdt" />IntelRdt
 
 **`intelRdt`** (object, OPTIONAL) represents the [Intel Resource Director Technology][intel-rdt-cat-kernel-interface].
-    If `intelRdt` is set, the runtime MUST write the container process ID to the `<container-id>/tasks` file in a mounted `resctrl` pseudo-filesystem, using the container ID from [`start`](runtime.md#start) and creating the `<container-id>` directory if necessary.
+    If `intelRdt` is set, the runtime MUST write the container process ID to the `tasks` file in a proper sub-directory in a mounted `resctrl` pseudo-filesystem. That sub-directory name is specified by `closID` parameter.
     If no mounted `resctrl` pseudo-filesystem is available in the [runtime mount namespace](glossary.md#runtime-namespace), the runtime MUST [generate an error](runtime.md#errors).
 
     If `intelRdt` is not set, the runtime MUST NOT manipulate any `resctrl` pseudo-filesystems.
 
 The following parameters can be specified for the container:
 
+* **`closID`** *(string, OPTIONAL)* - specifies the identity for RDT Class of Service (CLOS).
+    If `closID` is set, runtimes MUST create `closID` directory in a mounted `resctrl` pseudo-filesystem if it doesn't exist. If not set, runtimes MUST use the container ID from [`start`](runtime.md#start) and create the `<container-id>` directory.
+
 * **`l3CacheSchema`** *(string, OPTIONAL)* - specifies the schema for L3 cache id and capacity bitmask (CBM).
-    If `l3CacheSchema` is set, runtimes MUST write the value to the `schemata` file in the `<container-id>` directory discussed in `intelRdt`.
+    If `l3CacheSchema` is set, runtimes MUST write the value to the `schemata` file in that sub-directory discussed in `closID`. If not set, runtimes MUST NOT write to `schemata` files in any `resctrl` pseudo-filesystems.
 
-    If `l3CacheSchema` is not set, runtimes MUST NOT write to `schemata` files in any `resctrl` pseudo-filesystems.
+    If `closID` and `l3CacheSchema` both are set, runtimes MUST compare `l3CacheSchema` value with `schemata` file, and [generate an error](runtime.md#errors) if doesn't match.
 
 ### Example
 
@@ -508,6 +511,7 @@ Tasks inside the container only have access to the "upper" 80% of L3 cache id 0
 ```json
 "linux": {
     "intelRdt": {
+        "closID": "guaranteed_group",
         "l3CacheSchema": "L3:0=ffff0;1=3ff"
     }
 }

schema/config-linux.json

@@ -228,6 +228,9 @@
             "intelRdt": {
                 "type": "object",
                 "properties": {
+                    "closID": {
+                        "type": "string"
+                    },
                     "l3CacheSchema": {
                         "type": "string"
                     }

specs-go/config.go

@@ -624,6 +624,8 @@ type LinuxSyscall struct {
 // LinuxIntelRdt has container runtime resource constraints
 // for Intel RDT/CAT which introduced in Linux 4.10 kernel
 type LinuxIntelRdt struct {
+	// The identity for RDT Class of Service
+	ClosID string `json:"closID,omitempty"`
 	// The schema for L3 cache id and capacity bitmask (CBM)
 	// Format: "L3:<cache_id0>=<cbm0>;<cache_id1>=<cbm1>;..."
 	L3CacheSchema string `json:"l3CacheSchema,omitempty"`