[Qemu-devel] [RFC v4 5/9] configure: Enable/disable new qemu_{ld, st} excl insns

[Alvise Rigo <a.rigo@virtualopensystems.com>]

Introduce the new --enable-tcg-ldst-excl configure option to enable the
LL/SC operations only for those backends that support them.

Suggested-by: Jani Kokkonen <jani.kokkonen@huawei.com>
Suggested-by: Claudio Fontana <claudio.fontana@huawei.com>
Signed-off-by: Alvise Rigo <a.rigo@virtualopensystems.com>
---
 configure | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/configure b/configure
index 33b9455..c3ea3db 100755
--- a/configure
+++ b/configure
@@ -264,6 +264,7 @@ debug_tcg="no"
 debug="no"
 strip_opt="yes"
 tcg_interpreter="no"
+tcg_use_ldst_excl="no"
 bigendian="no"
 mingw32="no"
 gcov="no"
@@ -934,6 +935,10 @@ for opt do
   ;;
   --enable-tcg-interpreter) tcg_interpreter="yes"
   ;;
+  --disable-tcg-ldst-excl) tcg_use_ldst_excl="no"
+  ;;
+  --enable-tcg-ldst-excl) tcg_use_ldst_excl="yes"
+  ;;
   --disable-cap-ng)  cap_ng="no"
   ;;
   --enable-cap-ng) cap_ng="yes"
@@ -1392,6 +1397,18 @@ if test "$ARCH" = "unknown"; then
     fi
 fi
 
+# Check if the slow-path for atomic instructions is supported by the
+# TCG backend.
+case $cpu in
+    i386|x86_64|arm|aarch64)
+        ;;
+    *)
+        if test "$tcg_use_ldst_excl" = "yes"; then
+            error_exit "Load and store exclusive not supported for $cpu hosts"
+        fi
+        ;;
+esac
+
 # Consult white-list to determine whether to enable werror
 # by default.  Only enable by default for git builds
 z_version=`cut -f3 -d. $source_path/VERSION`
@@ -4526,6 +4543,7 @@ echo "Install blobs     $blobs"
 echo "KVM support       $kvm"
 echo "RDMA support      $rdma"
 echo "TCG interpreter   $tcg_interpreter"
+echo "use ld/st excl    $tcg_use_ldst_excl"
 echo "fdt support       $fdt"
 echo "preadv support    $preadv"
 echo "fdatasync         $fdatasync"
@@ -4903,6 +4921,9 @@ fi
 if test "$tcg_interpreter" = "yes" ; then
   echo "CONFIG_TCG_INTERPRETER=y" >> $config_host_mak
 fi
+if test "$tcg_use_ldst_excl" = "yes" ; then
+  echo "CONFIG_TCG_USE_LDST_EXCL=y" >> $config_host_mak
+fi
 if test "$fdatasync" = "yes" ; then
   echo "CONFIG_FDATASYNC=y" >> $config_host_mak
 fi
-- 
2.5.0