Re: segfault in xl create for HVM with PCI passthrough

[Atom2 <ariel.atom2@web2web.at>]

Am 28.10.14 um 17:04 schrieb Ian Campbell:
>>> You say in $subject that the failure is with PCI, is that because you've
>>> tried an HVM domain without and it is ok, or is it just that all your
>>> HVM domains happen to have passthrough enabled?
>> I haven't tried HVM domains without PCI passthrough (but PV domains w/o
>> PCI passthrough and they did not segfault) so far as all my HVM domains
>> require PCI devices (either at least a network card for pfsense - in
>> actual facts it's more than one that's being passed through - or a SATA
>> controller for my second HVM which is used as a storage VM).
>
> The VM doesn't need to be fully functional, it just needs to boot
> without crashing the toolstack. Just running your existing VM with the
> pci line commented out would be useful.
Before re-compiling the xen-tools I made a quick test as you suggested
and commented out the pci line from my config file ... and the boot menu 
showed up (which it did not before when the segfault happened).
I did not boot the pfsense vm any further as this might lead to a change 
in my configuration due to missing devices, but to me this at first 
sight seemed to indicate that is has to do with the PCI passthrough 
functionality.
Although as I did not want to boot the machine (and "xl shutdown" did
not work, not even with -F) I then decided to
	xl destroy pfsense
and that printed a segmentation fault message (in both the shell window
where I started the command from and the console window where the
boot-menu was shown) despite no PCI devices being passed through.

To also check PCI passthrough with a PV domain: I added a pci device to
a config file for a PV domain and started that with
	xl create voip -c
The boot menu appeared without issues. I then also tried
	xl destroy voip
from another window and that issued the following error messages in the
shell window (without using any -vvv option):

# xl destroy voip
libxl: error: libxl_pci.c:1247:do_pci_remove: xc_domain_irq_permission
irq=17
libxl: error: libxl_device.c:1127:libxl__wait_for_backend: Backend
/local/domain/0/backend/pci/4/0 not ready
libxl: error: libxl_pci.c:1247:do_pci_remove: xc_domain_irq_permission
irq=16
libxl: error: libxl_device.c:1127:libxl__wait_for_backend: Backend
/local/domain/0/backend/pci/4/0 not ready
libxl: error: libxl_pci.c:1247:do_pci_remove: xc_domain_irq_permission
irq=23
libxl: error: libxl_device.c:1127:libxl__wait_for_backend: Backend
/local/domain/0/backend/pci/4/0 not ready
Segmentation fault

The "Segmentation fault" message also appeared in both the console
window for the domU and the shell window.

I'll do the gdb stuff later today and provide you with the backtrace.
But that's probably going to be a few hours from now as it requires a
bit or preparation and time to re-compile and I need to do some other
stuff inbetween.

This all seems a bit strange to me at the moement, but I am sure with
your help we will arrive at the grounds of this.

Thanks and regards Atom