Hello, I am trying to debug an issue in QubesOS where a domain created by libvirt often does not have information stored about the console TTY path.
The relevant part of libvirt creates a domain using libxl_domain_create_new() and registers a callback (aop_console_how) that is supposed to fire when the console is available. The callback then calls libxl_console_get_tty(), but that fails with: 2020-01-06 11:52:30.952+0000: libxl: libxl.c:1853:libxl_console_get_tty: unable to read console tty path `/local/domain/4/console/tty': Resource temporarily unavailable Based on my reading of the libxl code, it's supposed to set the path in xenstore and then call the console_available callback, but only if the bootloader is configured. Otherwise, we call console_available at a later point (in domcreate_attach_devices()) and the path in xenstore is being set by xenconsoled independently. However, there is no guarantee that xenconsoled will do that before we call console_available. And indeed, looking at the traces from xenstored, the read and write of `.../console/tty` are ordered randomly depending on the machine. Should libxl wait for the information appearing in '.../console/tty' at this point? Perhaps similar as the code I see in xenconsoled client (xen/tools/console/client.c)? I would be happy to work on a patch but I'm unfamiliar with the project so I want to check my assumptions. (I am testing with Xen 4.8.5 because that's what the stable version of QubesOS uses, but as far as I can tell, that part has not changed since). Original QubesOS bug here: https://github.com/QubesOS/qubes-issues/issues/5156 -- Paweł Marczewski Invisible Things Lab
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