agent: add memory hotplug probe interface check in GetGuestDetails

In order to support memory hotplug br probe interface, firstly, we
need to verify whether guest kernel is capable of that. Typically
we will check if the path /sys/devices/system/memory/probe exists

Fixes: #442

Signed-off-by: Penny Zheng <penny.zheng@arm.com>

grpc.go

@@ -49,11 +49,12 @@ const (
 )
 
 var (
-	sysfsCPUOnlinePath       = "/sys/devices/system/cpu"
-	sysfsMemOnlinePath       = "/sys/devices/system/memory"
-	sysfsMemoryBlockSizePath = "/sys/devices/system/memory/block_size_bytes"
-	sysfsConnectedCPUsPath   = filepath.Join(sysfsCPUOnlinePath, "online")
-	containersRootfsPath     = "/run"
+	sysfsCPUOnlinePath          = "/sys/devices/system/cpu"
+	sysfsMemOnlinePath          = "/sys/devices/system/memory"
+	sysfsMemoryBlockSizePath    = "/sys/devices/system/memory/block_size_bytes"
+	sysfsMemoryHotplugProbePath = "/sys/devices/system/memory/probe"
+	sysfsConnectedCPUsPath      = filepath.Join(sysfsCPUOnlinePath, "online")
+	containersRootfsPath        = "/run"
 )
 
 type onlineResource struct {
@@ -1414,6 +1415,16 @@ func (a *agentGRPC) GetGuestDetails(ctx context.Context, req *pb.GuestDetailsReq
 		}
 	}
 
+	if req.MemHotplugProbe {
+		if _, err := os.Stat(sysfsMemoryHotplugProbePath); os.IsNotExist(err) {
+			details.SupportMemHotplugProbe = false
+		} else if err != nil {
+			return nil, err
+		} else {
+			details.SupportMemHotplugProbe = true
+		}
+	}
+
 	details.AgentDetails = a.getAgentDetails(ctx)
 
 	return &details, nil