On Thu Nov 16, 2023 at 1:55 PM AEST, Ani Sinha wrote: > > > > On 16-Nov-2023, at 6:45 AM, Nicholas Piggin <npig...@gmail.com> wrote: > > > > On Thu Nov 16, 2023 at 3:22 AM AEST, Daniel P. Berrangé wrote: > >> On Wed, Nov 15, 2023 at 01:14:53PM +0000, Daniel P. Berrangé wrote: > >>> On Wed, Nov 15, 2023 at 07:23:01AM +0100, Thomas Huth wrote: > >>>> On 15/11/2023 02.15, Nicholas Piggin wrote: > >>>>> On Wed Nov 15, 2023 at 4:29 AM AEST, Thomas Huth wrote: > >>>>>> On 14/11/2023 17.37, Philippe Mathieu-Daudé wrote: > >>>>>>> On 14/11/23 17:31, Thomas Huth wrote: > >>>>>>>> The tests seem currently to be broken. Disable them by default > >>>>>>>> until someone fixes them. > >>>>>>>> > >>>>>>>> Signed-off-by: Thomas Huth <th...@redhat.com> > >>>>>>>> --- > >>>>>>>> tests/avocado/reverse_debugging.py | 7 ++++--- > >>>>>>>> 1 file changed, 4 insertions(+), 3 deletions(-) > >>>>>>> > >>>>>>> Similarly, I suspect > >>>>>>> https://gitlab.com/qemu-project/qemu/-/issues/1961 > >>>>>>> which has a fix ready: > >>>>>>> https://lore.kernel.org/qemu-devel/20231110170831.185001-1-richard.hender...@linaro.org/ > >>>>>>> > >>>>>>> Maybe wait the fix gets in first? > >>>>>> > >>>>>> No, I applied Richard's patch, but the problem persists. Does this test > >>>>>> still work for you? > >>>>> > >>>>> I bisected it to 1d4796cd008373 ("python/machine: use socketpair() for > >>>>> console connections"), > >>>> > >>>> Maybe John (who wrote that commit) can help? > >>> > >>> I find it hard to believe this commit is a direct root cause of the > >>> problem since all it does is change the QEMU startup sequence so that > >>> instead of QEMU listening for a monitor connection, it is given a > >>> pre-opened monitor connection. > >>> > >>> At the very most that should affect the startup timing a little. > >>> > >>> I notice all the reverse debugging tests have a skip on gitlab > >>> with a comment: > >>> > >>> # unidentified gitlab timeout problem > >>> > >>> this makes be suspicious that John's patch has merely made this > >>> (henceforth undiagnosed) timeout more likely to ocurr. > >> > >> After an absolutely horrendous hours long debugging session I think > >> I figured out the problem. The QEMU process is blocking in > >> > >> qemu_chr_write_buffer > >> > >> spinning in the loop on EAGAIN. > > > > Great work. > > > > Why does this make the gdb socket give an empty response? Something > > just times out? > > > >> > >> The Python Machine() class has passed one of a pre-created socketpair > >> FDs for the serial port chardev. The guest is trying to write to this > >> and blocking. Nothing in the Machine() class is reading from the > >> other end of the serial port console. > >> > >> > >> Before John's change, the serial port uses a chardev in server mode > >> and crucially 'wait=off', and the Machine() class never opened the > >> console socket unless the test case wanted to read from it. > >> > >> IOW, QEMU had a background job setting there waiting for a connection > >> that would never come. > >> > >> As a result when QEMU started executing the guest, all the serial port > >> writes get sent into to the void. > >> > >> > >> So John's patch has had a semantic change in behaviour, because the > >> console socket is permanently open, and thus socket buffers are liable > >> to fill up. > >> > >> As a demo I increased the socket buffers to 1MB and everything then > >> succeeded. > >> > >> @@ -357,6 +360,10 @@ def _pre_launch(self) -> None: > >> > >> if self._console_set: > >> self._cons_sock_pair = socket.socketpair() > >> + self._cons_sock_pair[0].setsockopt(socket.SOL_SOCKET, > >> socket.SO_SNDBUF, 1024*1024); > >> + self._cons_sock_pair[0].setsockopt(socket.SOL_SOCKET, > >> socket.SO_RCVBUF, 1024*1024); > >> + self._cons_sock_pair[1].setsockopt(socket.SOL_SOCKET, > >> socket.SO_SNDBUF, 1024*1024); > >> + self._cons_sock_pair[1].setsockopt(socket.SOL_SOCKET, > >> socket.SO_RCVBUF, 1024*1024); > >> os.set_inheritable(self._cons_sock_pair[0].fileno(), True) > >> > >> # NOTE: Make sure any opened resources are *definitely* freed in > > > > So perhaps ppc64 fails just because it prints more to the console in early > > boot than other targets? > > > >> The Machine class doesn't know if anything will ever use the console, > >> so as is the change is unsafe. > >> > >> The original goal of John's change was to guarantee we capture early > >> boot messages as some test need that. > >> > >> I think we need to be able to have a flag to say whether the caller needs > >> an "early console" facility, and only use the pre-opened FD passing for > >> that case. Tests we need early console will have to ask for that guarantee > >> explicitly. > > > > The below patch makes this test work. Maybe as a quick fix it is > > better than disabling the test. > > > > I guess we still have a problem if a test invokes vm.launch() > > directly without subsequently waiting for a console pattern or > > doing something with the console as you say. Your suggesstion is > > add something like vm.launch(console=True) ? > > I think what he is saying is to add a new property for QEMUMachine() with > which the test can explicitly tell the machine init code that it is going to > drain the console logs. By default it can be false. When tests use > console_drainer, they can set the property to true and inspect the early > console logs after draining it.
Hmm... well we do have QEMUMachine.set_console already. Is this enough? If the test case is not going to drain or interact with the console then it could set it to false. Or am I missing something? Thanks, Nick
