virtcontainers: inherit parent's CPU constraint

Don't set a default CPU constraint if period and quota are not specified, that
way the container will inherit the CPU constraint from its parent. Container
creation won't fail if the parent CPU constraint is smaller than the default
number of vCPUs.

fixes kata-containers#1521

Signed-off-by: Julio Montes <[email protected]>
(cherry picked from commit 59e3956)
Signed-off-by: Ganesh Maharaj Mahalingam <[email protected]>

virtcontainers/cgroups.go

@@ -266,6 +266,8 @@ func (s *Sandbox) resources() (specs.LinuxResources, error) {
 }
 
 func (s *Sandbox) cpuResources() *specs.LinuxCPU {
+	// Use default period and quota if they are not specified.
+	// Container will inherit the constraints from its parent.
 	quota := int64(0)
 	period := uint64(0)
 	shares := uint64(0)
@@ -322,13 +324,6 @@ func (s *Sandbox) cpuResources() *specs.LinuxCPU {
 
 	cpu.Cpus = strings.Trim(cpu.Cpus, " \n\t,")
 
-	// use a default constraint for sandboxes without cpu constraints
-	if period == uint64(0) && quota == int64(0) {
-		// set a quota and period equal to the default number of vcpus
-		quota = int64(s.config.HypervisorConfig.NumVCPUs) * 100000
-		period = 100000
-	}
-
 	return validCPUResources(cpu)
 }