hypervisors: Confidential Guests do not support Memory hotplug

Similarly to VCPUs and Device hotplug, Confidential Guests also do not
support Memory hotplug.

Let's make it clear in the documentation and guard the code on both QEMU
and Cloud Hypervisor side to ensure we don't advertise Memory hotplug as
being supported when running Confidential Guests.

Signed-off-by: Fabiano Fidêncio <fabiano.fidencio@intel.com>

src/runtime/config/configuration-clh.toml.in

@@ -25,6 +25,7 @@ image = "@IMAGEPATH@"
 # * Does not work by design:
 #   - CPU Hotplug 
 #   - Device Hotplug
+#   - Memory Hotplug
 #
 # Default false
 # confidential_guest = true

src/runtime/config/configuration-qemu.toml.in

@@ -26,6 +26,7 @@ machine_type = "@MACHINETYPE@"
 # * Does not work by design:
 #   - CPU Hotplug 
 #   - Device Hotplug
+#   - Memory Hotplug
 #
 # Default false
 # confidential_guest = true

src/runtime/virtcontainers/clh.go

@@ -258,12 +258,14 @@ func (clh *cloudHypervisor) CreateVM(ctx context.Context, id string, network Net
 	clh.vmconfig.Memory.Shared = func(b bool) *bool { return &b }(true)
 	// Enable hugepages if needed
 	clh.vmconfig.Memory.Hugepages = func(b bool) *bool { return &b }(clh.config.HugePages)
-	hostMemKb, err := GetHostMemorySizeKb(procMemInfo)
-	if err != nil {
-		return nil
+	if !clh.config.ConfidentialGuest {
+		hostMemKb, err := GetHostMemorySizeKb(procMemInfo)
+		if err != nil {
+			return nil
+		}
+		// OpenAPI only supports int64 values
+		clh.vmconfig.Memory.HotplugSize = func(i int64) *int64 { return &i }(int64((utils.MemUnit(hostMemKb) * utils.KiB).ToBytes()))
 	}
-	// OpenAPI only supports int64 values
-	clh.vmconfig.Memory.HotplugSize = func(i int64) *int64 { return &i }(int64((utils.MemUnit(hostMemKb) * utils.KiB).ToBytes()))
 	// Set initial amount of cpu's for the virtual machine
 	clh.vmconfig.Cpus = chclient.NewCpusConfig(int32(clh.config.NumVCPUs), int32(clh.config.DefaultMaxVCPUs))
 

src/runtime/virtcontainers/qemu_amd64.go

@@ -189,7 +189,11 @@ func (q *qemuAmd64) memoryTopology(memoryMb, hostMemoryMb uint64, slots uint8) g
 // Is Memory Hotplug supported by this architecture/machine type combination?
 func (q *qemuAmd64) supportGuestMemoryHotplug() bool {
 	// true for all amd64 machine types except for microvm.
-	return q.qemuMachine.Type != govmmQemu.MachineTypeMicrovm
+	if q.qemuMachine.Type == govmmQemu.MachineTypeMicrovm {
+		return false
+	}
+
+	return q.protection == noneProtection
 }
 
 func (q *qemuAmd64) appendImage(ctx context.Context, devices []govmmQemu.Device, path string) ([]govmmQemu.Device, error) {

src/runtime/virtcontainers/qemu_arch_base.go

@@ -692,7 +692,7 @@ func (q *qemuArchBase) handleImagePath(config HypervisorConfig) {
 }
 
 func (q *qemuArchBase) supportGuestMemoryHotplug() bool {
-	return true
+	return q.protection == noneProtection
 }
 
 func (q *qemuArchBase) setIgnoreSharedMemoryMigrationCaps(ctx context.Context, qmp *govmmQemu.QMP) error {