[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] libxl: cannot start guest

On 05/22/12 16:20, Ian Campbell wrote:

> On Tue, 2012-05-22 at 15:03 +0100, Christoph Egger wrote:
>> On 05/22/12 15:21, Ian Campbell wrote:
>>> On Tue, 2012-05-22 at 14:18 +0100, Christoph Egger wrote:
>>>> I thinkIn xs_talkv() something must fail.
>>>>> The only thing which springs to mind is that it may generate an
>>>>> @IntroduceDomain watch event. However xl is single threaded so we won't
>>>>> process that event until we unwind to whichever point we do an event
>>>>> loop iteration, in which case the corruption would have to happen later
>>>>> than right after xs_introduce_domain().
>>>>> Did you manage to determine if "Bad file descriptor" was due to it being
>>>>> closed vs. the value being corrupted?
>>>> My suspicion is that
>>>>    if (msg.type != type)
>>>> in xs_talkv() is true.
>>> Yes, that definitely seems worth investigating.
>> Ok, I got it.
>> xenstored crashes due to dereferencing NULL pointer.
> Huh, xenstore has materially changed for quite a while (since February).
>> In xenstored_domain.c, map_interface()  *xcg_handle is NULL
>> and in xc_gnttab.c, xc_gnttab_map_grant_ref() it is dereferenced.
> This comes from 24757:aae516b78fce. Diego and Alex aren't around any
> more but CCing Daniel in case he remembers anything.
> I guess the original xc_gnttab_open which sets *xcg_handle is failing
> for you, I suppose that is to be expected on NetBSD? Either way it
> should still work after this has failed.
> All the >= checks on *xcg_handle seem wrong to me. Really they should be
> checking != NULL, since otherwise they don't actually discriminate the
> two cases! Does making that change help?

Yes, that helps! I can start guests again.


---to satisfy European Law for business letters:
Advanced Micro Devices GmbH
Einsteinring 24, 85689 Dornach b. Muenchen
Geschaeftsfuehrer: Alberto Bozzo, Andrew Bowd
Sitz: Dornach, Gemeinde Aschheim, Landkreis Muenchen
Registergericht Muenchen, HRB Nr. 43632

Xen-devel mailing list



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.