monitor: check if chardev can switch gcontext for OOB

Not all backends are able to switch gcontext. Those backends cannot
drive a OOB monitor (the monitor would then be blocking on main
thread).

For example, ringbuf, spice, or more esoteric input chardevs like
braille or MUX.

We already forbid MUX because not all frontends are ready to run outside
main loop.  Replace that by a context-switching feature check.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20181205203737.9011-5-marcandre.lureau@redhat.com>
[Error condition simplified, commit message adjusted accordingly]
Signed-off-by: Markus Armbruster <armbru@redhat.com>
This commit is contained in:
Marc-André Lureau 2018-12-06 00:37:34 +04:00 committed by Markus Armbruster
parent 9ac3788b0b
commit a9a0d9b99a

View File

@ -4562,9 +4562,10 @@ void monitor_init(Chardev *chr, int flags)
bool use_oob = flags & MONITOR_USE_OOB;
if (use_oob) {
if (CHARDEV_IS_MUX(chr)) {
if (!qemu_chr_has_feature(chr, QEMU_CHAR_FEATURE_GCONTEXT)) {
error_report("Monitor out-of-band is not supported with "
"MUX typed chardev backend");
"%s typed chardev backend",
object_get_typename(OBJECT(chr)));
exit(1);
}
if (use_readline) {