[Qemu-devel] [PATCH 2/5] configure: Don't allow user-only targets for unknown CPU architectures

[Peter Maydell <peter.maydell@linaro.org>]

For the user-only targets, we need to know something about the host CPU
architecture even if we are using the TCI interpreter rather than TCG.
(In particular user-exec.c has code for handling signals that needs
to know about that host's context structures.)

Specifically forbid building the user-only targets on unknown CPU
architectures, rather than allowing them to configure but then fail
when building user-exec.c.

This change drops supports for two configurations which were theoretically
possible before:
 * linux-user targets on M68K hosts using TCI
 * linux-user targets on HPPA hosts using TCI

We don't think anybody is actually trying to use these in practice, though:
 * interpreted TCG on a slow host CPU would be unusably slow
 * the m68k user-exec.c support is missing is_write detection so guest
   code which writes to the same page it is executing from was broken
   (will include any guest program using signals)
 * HPPA TCG backend support was dropped two and a half years ago
   with no complaints

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 configure | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/configure b/configure
index 7ab4e0b..62f93e3 100755
--- a/configure
+++ b/configure
@@ -1217,6 +1217,13 @@ esac
 QEMU_CFLAGS="$CPU_CFLAGS $QEMU_CFLAGS"
 EXTRA_CFLAGS="$CPU_CFLAGS $EXTRA_CFLAGS"
 
+# For user-mode emulation the host arch has to be one we explicitly
+# support, even if we're using TCI.
+if [ "$ARCH" = "unknown" ]; then
+  bsd_user="no"
+  linux_user="no"
+fi
+
 default_target_list=""
 
 mak_wilds=""
-- 
1.9.1