Re: [Xen-devel] BUG: unable to handle kernel paging request

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 10.04.14 at 08:21, <SMonderer@xxxxxxxxxxxxxxx> wrote:
> When trying to bind VF to igb_uio on a PV machine I get the following error 
> the module crashes
>       BUG: unable to handle kernel paging request Xen dmesg shows mm.c:618:d1 
> Could not get page ref for pfn df300 I'm new to dpdk so if you need any other 
> information let me know.

I'm afraid you'll need to do a little (more) debugging yourself first, not
the least because it's not clear what the driver you are using is trying
to achieve.

> [   90.348791] BUG: unable to handle kernel paging request at ffffc9000063e00c
> [   90.348796] IP: [<ffffffffa01542cf>] 
> igbuio_set_interrupt_mask.isra.2+0xbf/0xe0 [igb_uio]
> [   90.348802] PGD 98440067 PUD 98441067 PMD 97e47067 PTE 8010000000000464

While the function name above may hint at an attempt of the driver to
set the MSI-X mask bit (which should be trapped and emulated by
qemu), the PTE is clearly bogus: It references PFN 0 and has its
present bit clear. Not sure how/when that would happen - that's one
of the things to look into.

> (XEN) mm.c:807: d1: Forcing read-only access to MFN df300
> (XEN) mm.c:807: d0: Forcing read-only access to MFN df300
> (XEN) mm.c:807: d1: Forcing read-only access to MFN df300
> (XEN) mm.c:807: d1: Forcing read-only access to MFN df302
> (XEN) mm.c:807: d1: Forcing read-only access to MFN df300
> (XEN) mm.c:807: d0: Forcing read-only access to MFN df300

It's unlikely to be related to these, as they imply only the writable
bit gets cleared.

> (XEN) mm.c:618:d1 Could not get page ref for pfn df300

But it's likely to be related to this one, so for debugging purposes
forcing a stack trace to be generated (usually this message is
being accompanied by further ones, allowing to identify the code
path without a full stack trace) might help: Insert
dump_execution_state() right after the line issuing the message.

Jan


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