Re: 2.6.25-rc1 xen pvops regression

[Jeremy Fitzhardinge]

Joel Becker wrote:
> On Sat, Feb 16, 2008 at 01:44:26PM +1100, Jeremy Fitzhardinge wrote:
>   
> > Joel Becker wrote:
> >
> >     
> > > (XEN) mm.c:1825:d109 Bad type (saw 0000000028000001 != exp 
> > > 00000000e0000000) for mfn 3a2f0f (pfn f0)
> > > (XEN) mm.c:649:d109 Error getting mfn 3a2f0f (pfn f0) from L1 entry 
> > > 00000003a2f0f063 for dom109
> > > (XEN) mm.c:1825:d109 Bad type (saw 0000000028000001 != exp 
> > > 00000000e0000000) for mfn 3a2f0f (pfn f0)
> > > (XEN) mm.c:649:d109 Error getting mfn 3a2f0f (pfn f0) from L1 entry 
> > > 00000003a2f0f063 for dom109
> > > (XEN) mm.c:3331:d109 ptwr_emulate: could not get_page_from_l1e()
> > >   
> > >       
> > Hm, I have a suspicion about what this might be.  I'll haven't tried 
> > reproducing it yet though.
> >
> >     
> > > (XEN) Unhandled page fault in domain 109 on VCPU 0 (ec=0003)
> > > (XEN) Pagetable walk from 00000000c01687f0:
> > > (XEN)  L4[0x000] = 00000003a2933027 00000000000006cc
> > > (XEN)  L3[0x003] = 000000039afea027 0000000000000005
> > > (XEN)  L2[0x000] = 000000039bfb7067 0000000000001048 (XEN)  L1[0x168] = 
> > > 00000003a2e97061 0000000000000168
> > > (XEN) domain_crash_sync called from entry.S
> > > (XEN) Domain 109 (vcpu#0) crashed on cpu#2:
> > > (XEN) ----[ Xen-3.1.3-rc3  x86_64  debug=n  Not tainted ]----
> > > (XEN) CPU:    2
> > > (XEN) RIP:    e019:[<00000000c04040bd>]
> > >   
> > >       
> > What does this EIP correspond to in your kernel?  Also:
> >
> > c01687f0 c0417ab6 c040288f c040299a c0403270
> >
> > (as guesses of potential callers to try and work out a stack trace).
> >     
>
> 	ksymoops is no help at all, but I got these from objdump of
> vmlinux:
>
> c04040bd xen_set_pte
> c0417ab6 set_pte_present
> c040288f set_bit
> c040299a __raw_spin_unlock
> c0403270 __set_64bit

(My usual technique is use "gdb vmlinux" and "x/i 0x...." to do the 
lookup.) 

Unfortunately that doesn't narrow down what the kernel was actually 
trying to do at the time.  Clearly a set_pte; looks like someone is 
trying to create a writable mapping of an existing pte page.

Does "console=hvc0 earlyprintk=xen" on the kernel command line give any 
clue about how far it gets before crashing?

   J
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