Add SMT flag and disable by default am: 5b0cf33d7f

Original change: https://android-review.googlesource.com/c/device/google/cuttlefish/+/1612003

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I6e5930f90cead377fe300d52168ed083e2ff59b6

5 files changed, 34 insertions, 2 deletions

diff --git a/host/commands/assemble_cvd/flags.cc b/host/commands/assemble_cvd/flags.cc
index 72fc86a46..1705c51cf 100644
--- a/host/commands/assemble_cvd/flags.cc
+++ b/host/commands/assemble_cvd/flags.cc
@@ -270,6 +270,8 @@ DEFINE_bool(record_screen, false, "Enable screen recording. "
 
 DEFINE_bool(ethernet, false, "Enable Ethernet network interface");
 
+DEFINE_bool(smt, false, "Enable simultaneous multithreading (SMT/HT)");
+
 DEFINE_int32(vsock_guest_cid,
              cuttlefish::GetDefaultVsockCid(),
              "vsock_guest_cid is used to determine the guest vsock cid as well as all the ports"
@@ -401,7 +403,11 @@ CuttlefishConfig InitializeCuttlefishConfiguration(
                " does not work with vm_manager=" << FLAGS_vm_manager;
   }
 
+  CHECK(!FLAGS_smt || FLAGS_cpus % 2 == 0)
+      << "CPUs must be a multiple of 2 in SMT mode";
   tmp_config_obj.set_cpus(FLAGS_cpus);
+  tmp_config_obj.set_smt(FLAGS_smt);
+
   tmp_config_obj.set_memory_mb(FLAGS_memory_mb);
 
   tmp_config_obj.set_setupwizard_mode(FLAGS_setupwizard_mode);
@@ -591,6 +597,7 @@ CuttlefishConfig InitializeCuttlefishConfiguration(
   tmp_config_obj.set_enable_minimal_mode(FLAGS_enable_minimal_mode);
 
   tmp_config_obj.set_vhost_net(FLAGS_vhost_net);
+
   tmp_config_obj.set_record_screen(FLAGS_record_screen);
 
   tmp_config_obj.set_ethernet(FLAGS_ethernet);
diff --git a/host/libs/config/cuttlefish_config.cpp b/host/libs/config/cuttlefish_config.cpp
index 52bd4fcb0..7eabb8fc5 100644
--- a/host/libs/config/cuttlefish_config.cpp
+++ b/host/libs/config/cuttlefish_config.cpp
@@ -175,6 +175,8 @@ const char* kRecordScreen = "record_screen";
 
 const char* kEthernet = "ethernet";
 
+const char* kSmt = "smt";
+
 }  // namespace
 
 const char* const kGpuModeAuto = "auto";
@@ -872,6 +874,13 @@ bool CuttlefishConfig::record_screen() const {
   return (*dictionary_)[kRecordScreen].asBool();
 }
 
+void CuttlefishConfig::set_smt(bool smt) {
+  (*dictionary_)[kSmt] = smt;
+}
+bool CuttlefishConfig::smt() const {
+  return (*dictionary_)[kSmt].asBool();
+}
+
 // Creates the (initially empty) config object and populates it with values from
 // the config file if the CUTTLEFISH_CONFIG_FILE env variable is present.
 // Returns nullptr if there was an error loading from file
diff --git a/host/libs/config/cuttlefish_config.h b/host/libs/config/cuttlefish_config.h
index 2a09b53b3..42b366bac 100644
--- a/host/libs/config/cuttlefish_config.h
+++ b/host/libs/config/cuttlefish_config.h
@@ -341,6 +341,9 @@ class CuttlefishConfig {
   void set_record_screen(bool record_screen);
   bool record_screen() const;
 
+  void set_smt(bool smt);
+  bool smt() const;
+
   class InstanceSpecific;
   class MutableInstanceSpecific;
 
diff --git a/host/libs/vm_manager/crosvm_manager.cpp b/host/libs/vm_manager/crosvm_manager.cpp
index 95bb5b198..77c49bc25 100644
--- a/host/libs/vm_manager/crosvm_manager.cpp
+++ b/host/libs/vm_manager/crosvm_manager.cpp
@@ -160,6 +160,10 @@ std::vector<Command> CrosvmManager::StartCommands(
   });
   crosvm_cmd.AddParameter("run");
 
+  if (!config.smt()) {
+    crosvm_cmd.AddParameter("--no-smt");
+  }
+
   if (config.vhost_net()) {
     crosvm_cmd.AddParameter("--vhost-net");
   }
diff --git a/host/libs/vm_manager/qemu_manager.cpp b/host/libs/vm_manager/qemu_manager.cpp
index 376562c2d..db2a7a63b 100644
--- a/host/libs/vm_manager/qemu_manager.cpp
+++ b/host/libs/vm_manager/qemu_manager.cpp
@@ -175,9 +175,18 @@ std::vector<Command> QemuManager::StartCommands(
   qemu_cmd.AddParameter("-overcommit");
   qemu_cmd.AddParameter("mem-lock=off");
 
+  // Assume SMT is always 2 threads per core, which is how most hardware
+  // today is configured, and the way crosvm does it
   qemu_cmd.AddParameter("-smp");
-  qemu_cmd.AddParameter(config.cpus(), ",sockets=", config.cpus(),
-                        ",cores=1,threads=1");
+  if (config.smt()) {
+    CHECK(config.cpus() % 2 == 0)
+        << "CPUs must be a multiple of 2 in SMT mode";
+    qemu_cmd.AddParameter(config.cpus(), ",cores=",
+                          config.cpus() / 2, ",threads=2");
+  } else {
+    qemu_cmd.AddParameter(config.cpus(), ",cores=",
+                          config.cpus(), ",threads=1");
+  }
 
   qemu_cmd.AddParameter("-uuid");
   qemu_cmd.AddParameter(instance.uuid());