Re: [Xen-devel] segfault in xl create for HVM with PCI passthrough

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2014-10-28 at 16:39 +0100, Atom2 wrote:
> > Please can you run the command under gdb and grab a back trace. It would
> > also be useful to "xl -vvv create pfsense".
> >
> First of all attached please find the output of xl -vvv create pfsense. 
> I decided to attach a file as most of the output lines are longer than 
> 80 chars and therefore would most likely be folded by eMail clients.

Thanks.

> In terms of the last message before the segfault in my attached file it 
> seems to me that the bridge stuff was setup correctly as per the 
> following commands:

Agreed, it seems the crash happens after that sometime.

> With regards to gdb: I can certainly run the command under gdb after 
> including debug support to the executables - that's no big deal.
> I would, however, ask for your advice as to what I need to recompile 
> with debugger support? Is xen-tools (which includes xl) sufficient

I think just the Xen bits would be sufficient, at least to start with.

>  or 
> would you think that I also need to include debug support for gcc as the 
> library that is mentioned in /var/log/messages (libgcc_s.so.1) seems to 
> belong to the gcc package? Or is this library a red herring that just 
> works as the catch-all code getting and finally handling the segfault? 

I'd recommend ignoring it for now, in the event that the backtrace from
just the xen bits suggests a gcc issue that might change. My money right
now is on it being a xen issue though.

> Please advise. Tx.
> > [...]
> >> pci          = [ '04:00.0', '0a:08.0', '0a:0b.0' ]
> >
> > 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.

Ian


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