vmm: use RateLimiterGroup for virtio-blk devices

Add a 'rate_limit_groups' field to VmConfig that defines a set of
named RateLimiterGroups.

When the 'rate_limit_group' field of DiskConfig is defined, all
virtio-blk queues will be rate-limited by a shared RateLimiterGroup.
The lifecycle of all RateLimiterGroups is tied to the Vm.
A RateLimiterGroup may exist even if no Disks are configured to use
the RateLimiterGroup. Disks may be hot-added or hot-removed from the
RateLimiterGroup.

When the 'rate_limiter' field of DiskConfig is defined, we construct
an anonymous RateLimiterGroup whose lifecycle is tied to the Disk.
This is primarily done for api backwards compatability. Importantly,
the behavior is not the same! This implementation rate_limits the
aggregate bandwidth / iops of an individual disk rather than the
bandwidth / iops of an individual queue of a disk.

When neither the 'rate_limit_group' or the 'rate_limiter' fields of
DiskConfig is defined, the Disk is not rate-limited.

Signed-off-by: Thomas Barrett <tbarrett@crusoeenergy.com>

vmm/src/api/openapi/cloud-hypervisor.yaml

@@ -554,6 +554,10 @@ components:
           $ref: "#/components/schemas/MemoryConfig"
         payload:
           $ref: "#/components/schemas/PayloadConfig"
+        rate_limit_groups:
+          type: array
+          items:
+            $ref: "#/components/schemas/RateLimitGroupConfig"
         disks:
           type: array
           items:
@@ -812,6 +816,17 @@ components:
         Defines an IO rate limiter with independent bytes/s and ops/s limits.
         Limits are defined by configuring each of the _bandwidth_ and _ops_ token buckets.
 
+    RateLimitGroupConfig:
+      required:
+        - id
+        - rate_limiter_config
+      type: object
+      properties:
+        id:
+          type: string
+        rate_limiter_config:
+          $ref: "#/components/schemas/RateLimiterConfig"
+
     DiskConfig:
       required:
         - path
@@ -848,6 +863,8 @@ components:
           type: string
         serial:
           type: string
+        rate_limit_group:
+          type: string
 
     NetConfig:
       type: object