bugfix: plus default_memory when calculating mem size

We've noticed this caused regressions with the k8s-oom tests, and then
decided to take a step back and do this in the same way it was done
before 67972ec48a.

Moreover, this step back is also more reasonable in terms of the
controlling logic.

And by doing this we can re-enable the k8s-oom.bats tests, which is done
as part of this PR.

Fixes: #7271
Depends-on: github.com/kata-containers/tests#5705

Signed-off-by: Yushuo <y-shuo@linux.alibaba.com>

src/runtime-rs/crates/resource/src/cpu_mem/initial_size.rs

@@ -105,7 +105,12 @@ impl InitialSizeManager {
             hv.cpu_info.default_vcpus = self.resource.vcpu as i32
         }
         if self.resource.mem_mb > 0 {
-            hv.memory_info.default_memory = self.resource.mem_mb;
+            // since the memory overhead introduced by kata-agent and system components
+            // will really affect the amount of memory the user can use, so we choose to
+            // plus the default_memory here, instead of overriding it.
+            // (if we override the default_memory here, and user apllications still
+            // use memory as they orignally expected, it would be easy to OOM.)
+            hv.memory_info.default_memory += self.resource.mem_mb;
         }
         Ok(())
     }

tests/integration/kubernetes/k8s-oom.bats

@@ -9,15 +9,11 @@ load "${BATS_TEST_DIRNAME}/../../common.bash"
 load "${BATS_TEST_DIRNAME}/tests_common.sh"
 
 setup() {
-	[ "${KATA_HYPERVISOR}" == "dragonball" ] && skip "Test is currently failing, see: https://github.com/kata-containers/kata-containers/issues/7271"
-
 	pod_name="pod-oom"
 	get_pod_config_dir
 }
 
 @test "Test OOM events for pods" {
-	[ "${KATA_HYPERVISOR}" == "dragonball" ] && skip "Test is currently failing, see: https://github.com/kata-containers/kata-containers/issues/7271"
-
 	# Create pod
 	kubectl create -f "${pod_config_dir}/$pod_name.yaml"
 
@@ -33,8 +29,6 @@ setup() {
 }
 
 teardown() {
-	[ "${KATA_HYPERVISOR}" == "dragonball" ] && skip "Test is currently failing, see: https://github.com/kata-containers/kata-containers/issues/7271"
-
 	# Debugging information
 	kubectl describe "pod/$pod_name"
 	kubectl get "pod/$pod_name" -o yaml