backends: Introduce chr-testdev

From: Paolo Bonzini <pbonzini@redhat.com>

chr-testdev enables a virtio serial channel to be used for guest
initiated qemu exits. hw/misc/debugexit already enables guest
initiated qemu exits, but only for PC targets. chr-testdev supports
any virtio-capable target. kvm-unit-tests/arm is already making use
of this backend.

Currently there is a single command implemented, "q".  It takes a
(prefix) argument for the exit code, thus an exit is implemented by
writing, e.g. "1q", to the virtio-serial port.

It can be used as:
   $QEMU ... \
     -device virtio-serial-device \
     -device virtserialport,chardev=ctd -chardev testdev,id=ctd

or, use:
   $QEMU ... \
     -device virtio-serial-device \
     -device virtconsole,chardev=ctd -chardev testdev,id=ctd

to bind it to virtio-serial port0.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/qemu-char.c b/qemu-char.c
index 956be49ecd..6964a2d9fd 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -3256,6 +3256,7 @@ QemuOpts *qemu_chr_parse_compat(const char *label, const char *filename)
         strcmp(filename, "pty")     == 0 ||
         strcmp(filename, "msmouse") == 0 ||
         strcmp(filename, "braille") == 0 ||
+        strcmp(filename, "testdev") == 0 ||
         strcmp(filename, "stdio")   == 0) {
         qemu_opt_set(opts, "backend", filename);
         return opts;
@@ -4057,6 +4058,9 @@ ChardevReturn *qmp_chardev_add(const char *id, ChardevBackend *backend,
         chr = chr_baum_init();
         break;
 #endif
+    case CHARDEV_BACKEND_KIND_TESTDEV:
+        chr = chr_testdev_init();
+        break;
     case CHARDEV_BACKEND_KIND_STDIO:
         chr = qemu_chr_open_stdio(backend->stdio);
         break;