Add HSA_ENABLE_PEER_SDMA env variable

Add support for HSA_ENABLE_PEER_SDMA env variable that can be used to
disable use of SDMA engines for device-to-device transfers. Note that
setting HSA_ENABLE_SDMA=0 will disable all SDMA transfers and override
HSA_ENABLE_PEER_SDMA values.

Change-Id: I737b3c2b2efcf3ff237f98bc748f49b8252ed24a

runtime/hsa-runtime/core/util/flag.h

@@ -87,6 +87,9 @@ class Flag {
     var = os::GetEnvVar("HSA_ENABLE_SDMA");
     enable_sdma_ = (var == "0") ? SDMA_DISABLE : ((var == "1") ? SDMA_ENABLE : SDMA_DEFAULT);
 
+    var = os::GetEnvVar("HSA_ENABLE_PEER_SDMA");
+    enable_peer_sdma_ = (var == "0") ? SDMA_DISABLE : ((var == "1") ? SDMA_ENABLE : SDMA_DEFAULT);
+
     visible_gpus_ = os::GetEnvVar("ROCR_VISIBLE_DEVICES");
     filter_visible_gpus_ = os::IsEnvVarSet("ROCR_VISIBLE_DEVICES");
 
@@ -225,6 +228,8 @@ class Flag {
 
   SDMA_OVERRIDE enable_sdma() const { return enable_sdma_; }
 
+  SDMA_OVERRIDE enable_peer_sdma() const { return enable_peer_sdma_; }
+
   std::string visible_gpus() const { return visible_gpus_; }
 
   bool filter_visible_gpus() const { return filter_visible_gpus_; }
@@ -302,6 +307,7 @@ class Flag {
   bool enable_mwaitx_;
 
   SDMA_OVERRIDE enable_sdma_;
+  SDMA_OVERRIDE enable_peer_sdma_;
 
   bool filter_visible_gpus_;
   std::string visible_gpus_;