hotplug: add default_bridges to configuration file

default_bridges allows user specify how many PCI bridges
must be included in the VM, this allow to hot plug until
~150 devices

fixes #831

Signed-off-by: Julio Montes <julio.montes@intel.com>

Makefile

@@ -104,6 +104,8 @@ PROXYPATH := $(PKGLIBEXECDIR)/$(PROXYCMD)
 DEFVCPUS := 1
 # Default memory size in MiB
 DEFMEMSZ := 2048
+#Default number of bridges
+DEFBRIDGES := 1
 
 DEFDISABLEBLOCK := false
 DEFENABLEMEMPREALLOC := false
@@ -176,6 +178,7 @@ USER_VARS += SHIMPATH
 USER_VARS += SYSCONFDIR
 USER_VARS += DEFVCPUS
 USER_VARS += DEFMEMSZ
+USER_VARS += DEFBRIDGES
 USER_VARS += DEFDISABLEBLOCK
 USER_VARS += DEFENABLEMEMPREALLOC
 USER_VARS += DEFENABLEHUGEPAGES
@@ -229,6 +232,7 @@ const defaultRuntimeRun = "$(PKGRUNDIR)"
 
 const defaultVCPUCount uint32 = $(DEFVCPUS)
 const defaultMemSize uint32 = $(DEFMEMSZ) // MiB
+const defaultBridgesCount uint32 = $(DEFBRIDGES)
 const defaultDisableBlockDeviceUse bool = $(DEFDISABLEBLOCK)
 const defaultEnableMemPrealloc bool = $(DEFENABLEMEMPREALLOC)
 const defaultEnableHugePages bool = $(DEFENABLEHUGEPAGES)
@@ -299,6 +303,7 @@ $(GENERATED_FILES): %: %.in Makefile VERSION
 		-e "s|@SHIMPATH@|$(SHIMPATH)|g" \
 		-e "s|@DEFVCPUS@|$(DEFVCPUS)|g" \
 		-e "s|@DEFMEMSZ@|$(DEFMEMSZ)|g" \
+		-e "s|@DEFBRIDGES@|$(DEFBRIDGES)|g" \
 		-e "s|@DEFDISABLEBLOCK@|$(DEFDISABLEBLOCK)|g" \
 		-e "s|@DEFENABLEMEMPREALLOC@|$(DEFENABLEMEMPREALLOC)|g" \
 		-e "s|@DEFENABLEHUGEPAGES@|$(DEFENABLEHUGEPAGES)|g" \

config.go

@@ -57,6 +57,9 @@ const (
 
 	// supported agent component types
 	hyperstartAgentTableType = "hyperstart"
+
+	// the maximum amount of PCI bridges that can be cold plugged in a VM
+	maxPCIBridges uint32 = 5
 )
 
 var (
@@ -82,6 +85,7 @@ type hypervisor struct {
 	MachineType           string `toml:"machine_type"`
 	DefaultVCPUs          int32  `toml:"default_vcpus"`
 	DefaultMemSz          uint32 `toml:"default_memory"`
+	DefaultBridges        uint32 `toml:"default_bridges"`
 	DisableBlockDeviceUse bool   `toml:"disable_block_device_use"`
 	MemPrealloc           bool   `toml:"enable_mem_prealloc"`
 	HugePages             bool   `toml:"enable_hugepages"`
@@ -203,6 +207,18 @@ func (h hypervisor) defaultMemSz() uint32 {
 	return h.DefaultMemSz
 }
 
+func (h hypervisor) defaultBridges() uint32 {
+	if h.DefaultBridges == 0 {
+		return defaultBridgesCount
+	}
+
+	if h.DefaultBridges > maxPCIBridges {
+		return maxPCIBridges
+	}
+
+	return h.DefaultBridges
+}
+
 func (p proxy) path() string {
 	if p.Path == "" {
 		return defaultProxyPath
@@ -264,6 +280,7 @@ func newQemuHypervisorConfig(h hypervisor) (vc.HypervisorConfig, error) {
 		HypervisorMachineType: machineType,
 		DefaultVCPUs:          h.defaultVCPUs(),
 		DefaultMemSz:          h.defaultMemSz(),
+		DefaultBridges:        h.defaultBridges(),
 		DisableBlockDeviceUse: h.DisableBlockDeviceUse,
 		MemPrealloc:           h.MemPrealloc,
 		HugePages:             h.HugePages,
@@ -369,6 +386,7 @@ func loadConfiguration(configPath string, ignoreLogging bool) (resolvedConfigPat
 		HypervisorMachineType: defaultMachineType,
 		DefaultVCPUs:          defaultVCPUCount,
 		DefaultMemSz:          defaultMemSize,
+		DefaultBridges:        defaultBridgesCount,
 		MemPrealloc:           defaultEnableMemPrealloc,
 		HugePages:             defaultEnableHugePages,
 		Mlock:                 !defaultEnableSwap,

config/configuration.toml.in

@@ -26,6 +26,19 @@ machine_accelerators="@MACHINEACCELERATORS@"
 # > 255            --> will be set to 255
 default_vcpus = -1
 
+
+# Bridges can be used to hot plug devices.
+# Limitations:
+# * Currently only pci bridges are supported
+# * Until 30 devices per bridge can be hot plugged.
+# * Until 5 PCI bridges can be cold plugged per VM.
+#   This limitation could be a bug in qemu or in the kernel
+# Default number of bridges per POD/VM:
+# unspecified or 0   --> will be set to @DEFBRIDGES@
+# > 1 <= 5           --> will be set to the specified number
+# > 5                --> will be set to 5
+default_bridges = @DEFBRIDGES@
+
 # Default memory size in MiB for POD/VM.
 # If unspecified then it will be set @DEFMEMSZ@ MiB.
 #default_memory = @DEFMEMSZ@

config_test.go

@@ -133,7 +133,8 @@ func createAllRuntimeConfigFiles(dir, hypervisor string) (config testRuntimeConf
 		DefaultVCPUs:          defaultVCPUCount,
 		DefaultMemSz:          defaultMemSize,
 		DisableBlockDeviceUse: disableBlockDevice,
-		Mlock: !defaultEnableSwap,
+		DefaultBridges:        defaultBridgesCount,
+		Mlock:                 !defaultEnableSwap,
 	}
 
 	agentConfig := vc.HyperConfig{}
@@ -506,7 +507,8 @@ func TestMinimalRuntimeConfig(t *testing.T) {
 		DefaultVCPUs:          defaultVCPUCount,
 		DefaultMemSz:          defaultMemSize,
 		DisableBlockDeviceUse: defaultDisableBlockDeviceUse,
-		Mlock: !defaultEnableSwap,
+		DefaultBridges:        defaultBridgesCount,
+		Mlock:                 !defaultEnableSwap,
 	}
 
 	expectedAgentConfig := vc.HyperConfig{}
@@ -904,6 +906,23 @@ func TestGetDefaultConfigFile(t *testing.T) {
 	assert.Error(err)
 }
 
+func TestDefaultBridges(t *testing.T) {
+	assert := assert.New(t)
+
+	h := hypervisor{DefaultBridges: 0}
+
+	bridges := h.defaultBridges()
+	assert.Equal(defaultBridgesCount, bridges)
+
+	h.DefaultBridges = maxPCIBridges + 1
+	bridges = h.defaultBridges()
+	assert.Equal(maxPCIBridges, bridges)
+
+	h.DefaultBridges = maxPCIBridges
+	bridges = h.defaultBridges()
+	assert.Equal(maxPCIBridges, bridges)
+}
+
 func TestDefaultFirmware(t *testing.T) {
 	assert := assert.New(t)