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Re: [Xen-devel] Xen dom0 crash: "d0:v0: unhandled page fault (ec=0000)"

On Wed, 2010-10-20 at 09:54 +0100, Gianni Tedesco wrote:
> On Wed, 2010-10-20 at 00:31 +0100, Andreas Kinzler wrote:
> > On 19.10.2010 17:45, Gianni Tedesco wrote:
> > > ditto, I suspected a known bug in my gcc version which broke xchg
> > > because when I compiled with -O2 instead of -Os... the problem went away
> > > but then something else bad happened later (I forget the details, and it
> > > was too many config tweaks ago to get back to last time I had it working
> > > that well)
> > 
> > Jeremy, one user earlier reported that he found out that for him there 
> > seems to be a relation between kernel size and crash status. He just 
> > added/removed some options that could never influence the "crash status" 
> > (like adding/removing netfilter modules). With all the experiences here, 
> > is may be useful to check for code paths related to kernel size.
> > 
> > Regards Andreas

I have dmesg output from and the current broken

http://pastebin.com/3m0DpDdW - - broken
http://pastebin.com/yC4CzLaZ - - working

In the panic you can see that %rax contains what the kernel thinks is
xen_start_info (0xffffffff817d3000) and from the xen logs, that is

>From the kernel messages it looks like the e820 map is being calculated
incorrectly, leading to bad memory mappings being setup which somehow
end up nuking the pagetable entry for xen start info. The
last_pfn/max_arch_pfn end up being an order of magnitude larger even
though both are booted with identical xen and kernel commandline params.
Xen has dom0_mem=752M.


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