Re: [Xen-devel] HVM Driver Domain

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Mon, Jan 27, 2020 at 08:43:21PM +0000, tosher 1 wrote:
> Rojer,
> 
> > You can also start xl devd manually, as that will give you verbose
> > output of whats going on. In the driver domain:
> 
> > # killall xl
> > # xl -vvv devd -F
> 
> > That should give you detailed output of what's going on in the driver
> > domain, can you paste the output you get from the driver domain when
> > you try to start the failed guest?
> 
> I ran both commands in the driver domain. Before starting the domU, I get the 
> following verbose.
> 
> # sudo xl -vvv devd -F
> libxl: debug: libxl_device.c:1733:libxl_device_events_handler: Domain 0:ao 
> 0x556e3e940ef0: create: how=(nil) callback=(nil) poller=0x556e3e940c10
> libxl: debug: libxl_event.c:636:libxl__ev_xswatch_register: watch 
> w=0x7ffca33549d8 wpath=/local/domain/0/backend token=3/0: register slotnum=3
> libxl: debug: libxl_device.c:1790:libxl_device_events_handler: Domain 0:ao 
> 0x556e3e940ef0: inprogress: poller=0x556e3e940c10, flags=i
> libxl: debug: libxl_event.c:573:watchfd_callback: watch w=0x7ffca33549d8 
> wpath=/local/domain/0/backend token=3/0: event epath=/local/domain/0/backend
> libxl: debug: libxl_event.c:2227:libxl__nested_ao_create: ao 0x556e3e940600: 
> nested ao, parent 0x556e3e940ef0
> libxl: debug: libxl_event.c:1838:libxl__ao__destroy: ao 0x556e3e940600: 
> destroy

Are you sure this command is run on the driver domain?

The trace above shows 'xl devd' trying to get a watch on
/local/domain/0/backend which is the xenstore backend path of dom0.

BTW, are you creating the driver domain with 'driver_domain=1' in the
xl config file?

Which version of the tools are you using in the driver domain?

I'm quite sure 4.7 is too old, and 'xl devd' won't work properly in
that version.

> 
> I know this is not exactly what you asked for. Unfortunately, I don't see any 
> other verbose when try to start DomU. The error messages I get from the 
> failed DomU launch is as the following, where driver domain id is 7.
> 
> libxl: error: libxl_device.c:1075:device_backend_callback: Domain 8:unable to 
> add device with path /local/domain/7/backend/vif/8/0
> libxl: error: libxl_create.c:1458:domcreate_attach_devices: Domain 8:unable 
> to add nic devices
> libxl: error: libxl_device.c:1075:device_backend_callback: Domain 8:unable to 
> remove device with path /local/domain/7/backend/vif/8/0
> libxl: error: libxl_domain.c:1075:devices_destroy_cb: Domain 
> 8:libxl__devices_destroy failed
> libxl: error: libxl_domain.c:1003:libxl__destroy_domid: Domain 8:Non-existant 
> domain
> libxl: error: libxl_domain.c:962:domain_destroy_callback: Domain 8:Unable to 
> destroy guest
> libxl: error: libxl_domain.c:889:domain_destroy_cb: Domain 8:Destruction of 
> domain failed

I'm afraid this log is not very helpful, would be better if you could
paste the full logs, as there might be hints of what's going on in
other parts of the file.

> 
> On the other hand, if I run devd in Dom0, I get a lot of verbose when I try 
> to launch DomU, dependent on Driver Domain for networking. I am not sure if I 
> should paste it here. Please let me know what you think.

No, 'xl devd' in dom0 is not useful, as it will interact badly with
the toolstack also running from dom0.

Roger.

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