diff --git a/config/opal_check_cma.m4 b/config/opal_check_cma.m4
index 8ae5797dcf4..2930debf911 100644
--- a/config/opal_check_cma.m4
+++ b/config/opal_check_cma.m4
@@ -18,23 +18,45 @@
 # --------------------------------------------------------
 # check if cma support is wanted.
 AC_DEFUN([OPAL_CHECK_CMA],[
-    if test -z "$ompi_check_cma_happy" ; then
-	OPAL_VAR_SCOPE_PUSH([ompi_check_cma_need_defs ompi_check_cma_kernel_version ompi_check_cma_CFLAGS])
-
-	AC_ARG_WITH([cma],
-                    [AC_HELP_STRING([--with-cma],
-                                    [Build Cross Memory Attach support (default: autodetect)])])
-
-	# Enable CMA support by default if process_vm_readv is defined in glibc
-	AC_CHECK_FUNC(process_vm_readv, [ompi_check_cma_need_defs=0],
-		      [ompi_check_cma_need_defs=1])
-
-	if test $ompi_check_cma_need_defs = 1 ; then
-	    ompi_check_cma_CFLAGS="$CFLAGS"
-	    # Need some extra include paths to locate the appropriate headers
-	    CFLAGS="$CFLAGS -I${srcdir} -I${srcdir}/opal/include"
-	    AC_MSG_CHECKING([if internal syscall numbers for Linux CMA work])
-	    AC_RUN_IFELSE([AC_LANG_PROGRAM([[
+    AC_ARG_WITH([cma],
+                [AC_HELP_STRING([--with-cma],
+                                [Build Cross Memory Attach support (default: autodetect)])])
+
+    # We only need to do the back-end test once
+    if test -z "$opal_check_cma_happy" ; then
+        OPAL_CHECK_CMA_BACKEND
+    fi
+
+    AS_IF([test $opal_check_cma_happy -eq 1],
+          [$2],
+          [if test "$with_cma" = "yes"; then
+               AC_MSG_WARN([--with-cma support requested, but not available])
+               AC_MSG_ERROR([Cannot continue])
+           fi
+           $3])
+])
+
+AC_DEFUN([OPAL_CHECK_CMA_BACKEND],
+[
+    OPAL_VAR_SCOPE_PUSH([opal_check_cma_need_defs opal_check_cma_kernel_version opal_check_cma_CFLAGS opal_check_cma_msg])
+
+    # Some systems have process_cm_readv() in libc, which means CMA is
+    # supported.  Other systems do not have process_cm_readv() in
+    # libc, but have support for it in the kernel if we invoke it
+    # directly.  Check for both.
+    AC_CHECK_HEADERS([sys/prctl.h])
+
+    AC_CHECK_FUNC([process_vm_readv], [opal_check_cma_need_defs=0],
+                  [opal_check_cma_need_defs=1])
+    AC_DEFINE_UNQUOTED([OPAL_CMA_NEED_SYSCALL_DEFS],
+                       [$opal_check_cma_need_defs],
+                       [Need CMA syscalls defined])
+    if test $opal_check_cma_need_defs -eq 1 ; then
+        opal_check_cma_CFLAGS=$CFLAGS
+        # Need some extra include paths to locate the appropriate headers
+        CFLAGS="$CFLAGS -I${srcdir} -I${srcdir}/opal/include"
+        AC_MSG_CHECKING([if internal syscall numbers for Linux CMA work])
+        AC_RUN_IFELSE([AC_LANG_PROGRAM([[
 #include <stdlib.h>
 #include <stdint.h>
 #include <string.h>
@@ -88,31 +110,23 @@ static void do_check (pid_t pid, int *in, int *out)
     /* all good */
     return 0;
 ]])],
-			  [AC_MSG_RESULT([yes])
-			   ompi_check_cma_happy="yes"],
-			  [AC_MSG_RESULT([no])
-			   ompi_check_cma_happy="no"],
-			  [AC_MSG_RESULT([no (cross-compiling)])
-			   ompi_check_cma_happy="no"])
-	    CFLAGS="$ompi_check_cma_CFLAGS"
-	else
-	    ompi_check_cma_happy="yes"
-	fi
-
-	# If the user specifically requests CMA go ahead and enable it even
-	# if the glibc version does not support process_vm_readv
-	if test "x$with_cma" = "xyes" || test "$ompi_check_cma_happy" = "yes" ; then
-            ompi_check_cma_happy="yes"
-            AC_DEFINE_UNQUOTED([OPAL_CMA_NEED_SYSCALL_DEFS],
-                [$ompi_check_cma_need_defs],
-                [Need CMA syscalls defined])
-            AC_CHECK_HEADERS([sys/prctl.h])
-	fi
-
-	OPAL_VAR_SCOPE_POP
-
-	OPAL_SUMMARY_ADD([[Transports]],[[Shared memory/Linux CMA]],[$1],[$ompi_check_cma_happy])
+		      [AC_MSG_RESULT([yes])
+		       opal_check_cma_happy=1],
+		      [AC_MSG_RESULT([no])
+		       opal_check_cma_happy=0],
+		      [AC_MSG_RESULT([no (cross-compiling)])
+		       opal_check_cma_happy=0])
+	CFLAGS=$opal_check_cma_CFLAGS
+    else
+        # If we didn't need the defs, then we have process_vm_readv(),
+        # and CMA is happy.
+	opal_check_cma_happy=1
     fi
 
-    AS_IF([test "$ompi_check_cma_happy" = "yes"], [$2], [$3])
+    OPAL_VAR_SCOPE_POP
+
+    AS_IF([test $opal_check_cma_happy -eq 1],
+          [opal_check_cma_msg=yes],
+          [opal_check_cma_msg=no])
+    OPAL_SUMMARY_ADD([[Transports]],[[Shared memory/Linux CMA]],[$1],[$opal_check_cma_msg])
 ])