Re: Tapdisk failures / kernel general protection fault at xen 4.0.2rc3 / kernel pvops 2.6.32.36

[Daniel Stodden <daniel.stodden@citrix.com>]

On Thu, 2011-04-14 at 12:38 -0400, Daniel Stodden wrote:
> On Thu, 2011-04-14 at 09:15 -0400, Konrad Rzeszutek Wilk wrote:
> > On Wed, Apr 13, 2011 at 06:02:13PM -0300, Gerd Jakobovitsch wrote:
> > > I'm trying to run several VMs (linux hvm, with tapdisk:aio disks at
> > > a storage over nfs) on a CentOS system, using the up-to-date version
> > > of xen 4.0 / kernel pvops 2.6.32.x stable. With a configuration
> > > without (most of) debug activated, I can start several instances -
> > > I'm running 7 of them - but shortly afterwards the system stops
> > > responding. I can't find any information on this.
> > 
> > First time I see it.
> > > 
> > > Activating several debug configuration items, among them
> > > DEBUG_PAGEALLOC, I get an exception as soon as I try to start up a
> > > VM. The system reboots.
> > 
> > Oooh, and is the log below from that situation?
> > 
> > Daniel, any thoughs?
> 
> ---
> 	  Unmap pages from the kernel linear mapping after free_pages().
> 	  This results in a large slowdown, but helps to find certain types
> 	  of memory corruption.
> 
> Stunning. Our I/O page allocator is a sort of twisted mempool. Unless
> the allocation is explicitly modified in sysfs/, everything should stay
> pinned. We might be just tripping over debug code alone, but I didn't
> figure it out yet.

Ah, that's just missing Dominic's spinlock fix. 

http://xenbits.xen.org/gitweb/?p=people/dstodden/linux.git;a=commit;h=a765257af7e28c41bd776c3e03615539597eb592

Daniel