Re: [PATCH 3/3] iotests/migrate-cpr-exec: cover chardevs with logfile= #VSTOR-148304

[Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>]

One important case isn't covered. Namely, when source does NOT save the
log FD and target has to proceed without it - what we saw in the
VSTOR-148304.

1. Start with -chardev pty,id=char0 (no log) and isa-serial.
2. In the pre-CPR hook, replace that arg with
pty,id=char0,logfile=<BAD_LOG>.
3. After CPR, check that the VM is still running and that BAD_LOG was
not created (put it in an existing directory, so a reopen by path would
show up).
4. After shutdown, check that self.vm.get_log() contains log file was
not preserved, continuing without it. The exec'd QEMU inherits the old
process's stderr, so the warning ends up in the same log.

Please add this case.


On 10/2/26 7:48 PM, Denis V. Lunev wrote:
> From: Denis V. Lunev <den@openvz.org>
> 
> Run a console pty with its log in an fdset, a guest agent socket and a
> second QMP monitor, each with a log, through cpr-exec with a command
> line whose logfile paths cannot be created, as libvirt's is. Cover
> chardev-change to a new log for pty and socket, and a failed
> chardev-change, whose rollback must keep the old log preserved.
> 
> Signed-off-by: Denis V. Lunev <den@openvz.org>
> ---
>  tests/qemu-iotests/tests/migrate-cpr-exec     | 132 ++++++++++++++++++
>  tests/qemu-iotests/tests/migrate-cpr-exec.out |   4 +-
>  2 files changed, 134 insertions(+), 2 deletions(-)
> 
> diff --git a/tests/qemu-iotests/tests/migrate-cpr-exec b/tests/qemu-iotests/tests/migrate-cpr-exec
> index 51e6cbcd659..e8a6c502c84 100755
> --- a/tests/qemu-iotests/tests/migrate-cpr-exec
> +++ b/tests/qemu-iotests/tests/migrate-cpr-exec
> @@ -288,6 +288,138 @@ class TestCprExec(iotests.QMPTestCase):
>              '-device', 'isa-serial,chardev=char0')
>          self._test_cpr(pre_cpr_hook=change_socket)
>  
> +    BAD_LOG = os.path.join(iotests.test_dir, 'nonexistent', 'chr.log')
> +
> +    def _serial_write(self, data: str) -> None:
> +        for c in data:
> +            self.vm.qtest(f'outb 0x3f8 {ord(c)}')
> +
> +    def _open_files(self) -> set:
> +        fd_dir = f'/proc/{self.vm.get_pid()}/fd'
> +        return {os.readlink(os.path.join(fd_dir, fd))
> +                for fd in os.listdir(fd_dir)}

listdir() and readlink() are racy here.  Incoming migration cleanup may
still be closing fds at that point, so readlink can raise
FileNotFoundError. Skip fds that disappear with a try/except.

Andrey