cgroup: add cgroup v2 support

allow users to specify cgroup v2 resources.

Each element in the map refers to a file in the cgroup v2 hierarchy
and the element value has its content.

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

config-linux.md

@@ -494,6 +494,31 @@ You MUST specify at least one of the `hcaHandles` or `hcaObjects` in a given ent
 }
 ```
 
+## <a name="configLinuxUnified" />Unified
+
+**`unified`** (object, OPTIONAL) allows cgroup v2 parameters to be to be set and modified for the container.
+
+Each key in the map refers to a file in the cgroup unified hierarchy.
+
+The OCI runtime MUST ensure that the needed cgroup controllers are enabled for the cgroup.
+
+Configuration unknown to the runtime MUST still be written to the relevant file.
+
+The runtime MUST generate an error when the configuration refers to a cgroup controller that is not present or that cannot be enabled.
+
+### Example
+
+```json
+"unified": {
+    "io.max": "259:0 rbps=2097152 wiops=120\n253:0 rbps=2097152 wiops=120",
+    "hugetlb.1GB.max": "1073741824"
+}
+```
+
+If a controller is enabled on the cgroup v2 hierarchy but the configuration is provided for the cgroup v1 equivalent controller, the runtime MAY attempt a conversion.
+
+If the conversion is not possible the runtime MUST generate an error.
+
 ## <a name="configLinuxIntelRdt" />IntelRdt
 
 **`intelRdt`** (object, OPTIONAL) represents the [Intel Resource Director Technology][intel-rdt-cat-kernel-interface].

schema/config-linux.json

@@ -34,6 +34,9 @@
             "resources": {
                 "type": "object",
                 "properties": {
+                    "unified": {
+                        "$ref": "defs.json#/definitions/mapStringString"
+                    },
                     "devices": {
                         "type": "array",
                         "items": {

specs-go/config.go

@@ -372,6 +372,8 @@ type LinuxResources struct {
 	// Limits are a set of key value pairs that define RDMA resource limits,
 	// where the key is device name and value is resource limits.
 	Rdma map[string]LinuxRdma `json:"rdma,omitempty"`
+	// Unified resources.
+	Unified map[string]string `json:"unified,omitempty"`
 }
 
 // LinuxDevice represents the mknod information for a Linux special device file