[RFC PATCH] virt-manager: console disconnected after rebooting virtual machine in Xen mode

[Charles Arnold]

On 1/20/22 12:12 PM, Cole Robinson wrote:
> On 10/13/21 3:30 PM, Charles Arnold wrote:
>> Running with virt-manager 3.2.0, not a problem in 2.2.1.
>>
>> When rebooting an HVM guest on Xen, virt-manager gets a disconnected
>> event which closes the viewer. See
>> self._viewer.connect("disconnected", self._viewer_disconnected).
>> Running on KVM, this event does not seem to occur on VM reboot.
>>
>> Both Xen and KVM get a state changed event,
>> self.vm.connect("state-changed", self._vm_state_changed_cb)
>> but for Xen, the viewer is gone due to the prior disconnect and when
>> calling into _activate_default_console_page(), the viewer does not
>> exist nor does it get created.
>> The VM comes up fine but you need to close the console window and
>> open it again to see the running VM.
>>
>> This patch resolves the issue for me.
>>
>> diff --git a/virtManager/details/console.py
>> b/virtManager/details/console.py
>> index fafb7202..f8a005ee 100644
>> --- a/virtManager/details/console.py
>> +++ b/virtManager/details/console.py
>> @@ -913,6 +913,8 @@ class vmmConsolePages(vmmGObjectUI):
>>               return
>>
>>           cpage = self.widget("console-pages").get_current_page()
>> +        if cpage == _CONSOLE_PAGE_GRAPHICS:
>> +            self._init_viewer()
>>           if cpage != _CONSOLE_PAGE_UNAVAILABLE:
>>               return
>>
>>
> Sorry for the long delayed response. Thanks for analyzing this. I think
> I've seen some similar presenting issue with qemu but it's been hard to
> reproduce.
>
> The flow in console.py is confusing despite my previous cleanup
> attempts. There's two error pages: _CONSOLE_PAGE_GRAPHICS with subpage
> _GFX_PAGE_UNAVAILABLE, and _CONSOLE_PAGE_UNAVAILABLE
>
> The former is meant to be for fatal connection errors, which should
> block simple attempts to reconnect. So the error is preserved on screen
> unless the dialog is closed+reopened. Otherwise an error may come in but
> quickly get wiped out by a VM XML change event, which would attempt to
> reconnect to the VM, possibly asking for auth, etc.
>
> _CONSOLE_PAGE_UNAVAILABLE is lighter weight. This is the 'guest not
> running' screen, and a few others. If the VM is running and a state
> change event comes in, and we are on this page, we attempt to connect to
> the viewer (like when you click 'run' on an open details window).
>
> Unfortunately your patch makes the two cases act identical, which we
> don't want for the current code IMO
>
> The issue in this case is that viewer-disconnected is overloaded, since
> it can trigger for error conditions (like ssh tunnel problems), or for
> normal disconnects like this reboot case. The former should block
> console reconnection, the latter shouldn't since we have no useful error
> feedback to report.
>
> Can you try this patch and see if it fixes your case?
>
> diff --git a/virtManager/details/console.py b/virtManager/details/console.py
> index fafb7202..9b1e5db5 100644
> --- a/virtManager/details/console.py
> +++ b/virtManager/details/console.py
> @@ -814,14 +814,23 @@ class vmmConsolePages(vmmGObjectUI):
>               return
>
>           msg = _("Viewer was disconnected.")
> +        errmsg = ""
>           if errdetails:
> -            msg += "\n" + errdetails
> +            errmsg += "\n" + errdetails
>           if ssherr:
>               log.debug("SSH tunnel error output: %s", ssherr)
> -            msg += "\n\n"
> -            msg += _("SSH tunnel error output: %s") % ssherr
> +            errmsg += "\n\n"
> +            errmsg += _("SSH tunnel error output: %s") % ssherr
>
> -        self._activate_gfx_unavailable_page(msg)
> +        if errmsg:
> +            self._activate_gfx_unavailable_page(msg + errmsg)
> +            return
> +
> +        # If no error message was reported, this isn't a clear graphics
> +        # error that should block reconnecting. So use the top level
> +        # 'VM unavailable' page which makes it easier for the user to
> +        # reconnect.
> +        self._activate_vm_unavailable_page(msg)
>
>       def _viewer_disconnected(self, ignore, errdetails, ssherr):
>           self._activate_gfx_unavailable_page(_("Viewer disconnected."))
>
>
>
> Thanks,
> Cole
>

Yes, I can confirm that this patch resolves the problem.

Thank you!

- Charles