+ /* qemu sometimes needs this option to enable hardware
+ * virtualization, but some versions of 'qemu-kvm' will use KVM
+ * regardless (even where this option appears in the help text).
+ * It is rumoured that there are versions of qemu where supplying
+ * this option when hardware virtualization is not available will
+ * cause qemu to fail, so we we have to check at least that
+ * /dev/kvm is openable. That's not reliable, since /dev/kvm
+ * might be openable by qemu but not by us (think: SELinux) in
+ * which case the user would not get hardware virtualization,
+ * although at least shouldn't fail. A giant clusterfuck with the
+ * qemu command line, again.
+ */
+ if (qemu_supports (g, "-enable-kvm") &&
+ is_openable (g, "/dev/kvm", O_RDWR))
+ add_cmdline (g, "-enable-kvm");
+
+ /* Newer versions of qemu (from around 2009/12) changed the
+ * behaviour of monitors so that an implicit '-monitor stdio' is
+ * assumed if we are in -nographic mode and there is no other
+ * -monitor option. Only a single stdio device is allowed, so
+ * this broke the '-serial stdio' option. There is a new flag
+ * called -nodefaults which gets rid of all this default crud, so
+ * let's use that to avoid this and any future surprises.
+ */
+ if (qemu_supports (g, "-nodefaults"))
+ add_cmdline (g, "-nodefaults");