Re: [Xen-devel] [BUG] XEN domU crash when PV grub chainloads 32-bit domU grub

[Andreas Sundstrom <sunkan+lists.xen-devel@xxxxxxxx>]

Citerar Ian Campbell <ian.campbell@xxxxxxxxxx>:

> On Wed, 2015-09-23 at 00:37 +0200, Samuel Thibault wrote:
> > Andreas Sundstrom, le Mon 21 Sep 2015 22:03:22 +0200, a Ãcrit :
> > > Note that my original thought was that this bug probably is within
> > > GRUB.
> >
> > It's probably in the GRUB implementation of loading the domU GRUB, since
> > you say that pvgrub1 loads it fine.
> >
> > > (XEN) domain_crash_sync called from entry.S: fault at ffff82d08021feb0
> > > compat_create_bounce_frame+0xc6/0xde
> >
> > So it's inside xen entry code...
> >
> > > (XEN) Guest stack trace from esp=005a5ff0:
> >
> > This looks like the end of the stack
> >
> > > (XEN) 00000010 00000000 0001e019 00010046 0016b38b 0016b38a 0016b389
> > > 0016b388
> > > (XEN) 0016b387 0016b386 0016b385 0016b384 0016b383 0016b382 0016b381
> > > 0016b380
> > [...]
> >
> > and this looks like a lot of consecutive numbers.  Perhaps we simply
> > somehow overflow?  Did you try giving less memory to the domU?
> Along those lines, if the _host_ has buckets of RAM then might it be worth
> restricting it in case the issue is with getting MFNs which are not
> representably by the 32-bit PV interfaces? (IIRC the limit is ~160G due to
> the size of the m2p hole, a 32-bit MFN spans 16TB so it's unlikely to be
> that).
>
> Likewise maybe the issue is with full addresses which don't fit in a 32-bit
> number (which is maybe more likely to happen if grub uses a 1:1 mapping
> like I would guess it does), so limiting the host to <4GB might also be
> interesting?
If this was meant for me I will need more information to understand  
what to test.
dom0 has either 12G or 8G memory in my test machines if that makes a  
difference.
/Andreas


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