Attempt to disable FPU if using no-FPU pk/bbl

machine/minit.c

@@ -61,8 +61,9 @@ static void fp_init()
     init_fp_reg(i);
   write_csr(fcsr, 0);
 #else
-  if (supports_extension('D'))
+  uintptr_t fd_mask = (1 << ('F' - 'A')) | (1 << ('D' - 'A'));
-    die("FPU unexpectedly found; recompile with -mhard-float");
+  clear_csr(misa, fd_mask);
+  assert(!(read_csr(misa) & fd_mask));
 #endif
 }