[libvirt] Seeking for advice on 'virsh console' problems debugging

[Roman Bogorodskiy]

Hi,

I've been trying to understand why 'virsh console' doesn't work on
FreeBSD for some time and now I feel like I got stuck.

Background of the problem. Some time ago I started implementing console
support for the bhyve driver. I initially implemented it using nmdm(4)
device:

http://www.freebsd.org/cgi/man.cgi?query=nmdm&sektion=4&manpath=FreeBSD+10.0-stable

But 'virsh console' didn't work on it and exited immediately.

I though that it could be nmdm compatibility issue and decided to go
with the plan /dev/pts devices. But I got the same problem with it.

So I decided to try use console with qemu driver. And... I got the same
problem.

After some investigation, I spotted this block in tools/virsh-console.c:376

    while (!con->quit) {
        if (virCondWait(&con->cond, &con->lock) < 0) {
            VIR_ERROR(_("unable to wait on console condition"));
            goto cleanup;
        }
    }

The strange thing is that it doesn't look con->lock mutex before
waiting. 

FreeBSD man page for pthread_cond_wait() says that it errors in that
situation:

     [EPERM]            The specified mutex was not locked by the
     calling thread.

I replaced VIR_ERROR with virReportSystemError and it returns EPERM
indeed. So I've added virMutexLock() before calling virCondWait() and it
partially solved the problem for me -- 'virsh console' stopped exiting
immediately.

Actually, it started output for guest, but it's badly formatted: it
includes lots and lots of whitespaces. Input doesn't work properly
(cannot type in sensible stuff).

Here's a sample output, even libvirt messages are badly formatted (I
added some debug prints along the way).

http://people.freebsd.org/~novel/misc/ttyweirdness.png

So, e.g. dmesg output for the guest looks almost the same.

Looks like there's something wrong with the terminal settings, but how
could that be debugged?

PS Worth to mention that 'cu' worked all the time for me on these
devices (both created by bhyve and qemu).

Roman Bogorodskiy
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