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[Xen-devel] Re: xen crash during Dom0 boot

To: Christoph Egger <Christoph.Egger@xxxxxxx>
Subject: [Xen-devel] Re: xen crash during Dom0 boot
From: Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Date: Fri, 15 Apr 2011 09:36:37 +0100
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At 12:18 +0100 on 14 Apr (1302783510), Christoph Egger wrote:
> (XEN) mm.c:832:d0 Bad L1 flags 400000
> (XEN) mm.c:1256:d0 Failure in alloc_l1_table: entry 0
> (XEN) mm.c:2216:d0 Error while validating mfn 2225e0 (pfn 3f21) for type 
> 1000000000000000: caf=8000000000000003 taf=1000000000000001
> (XEN) mm.c:3026:d0 Error while pinning mfn 2225e0
> (XEN) traps.c:451:d0 Unhandled invalid opcode fault/trap [#6] on VCPU 0 
> [ec=0000]
> (XEN) domain_crash_sync called from entry.S
> (XEN) Domain 0 (vcpu#0) crashed on cpu#0:

OK, this is a dom0 crash rather than a Xen crash; it's just that Xen
reboots because dom0 has died. 

> The reason is that guest_walk_tables() in xen/arch/x86/mm/guest_walk.c  fakes 
> l1e entries for 2mb pages but not for 1gb pages.
> A workaround is to assign the Dom0 not more than 2 GB RAM  via
> the dom0_mem  xen boot parameter.
> This can only be reproduced with Dom0 kernels which use the autotranslation 
> feature (Linux Dom0 does, NetBSD Dom0 doesn't, don't know about other Dom0).

The autotranslation feature is _very_ bitrotted; I'd be amazed if it works
at all.  AFAIK linux dom0 doesn't use it (and can't sensibly use it since
it needs to know about bus addresses to run its drivers.).

Do you just mean that it happens on linux dom0 and not NetBSD or have
you done a more specific test?


Tim Deegan <Tim.Deegan@xxxxxxxxxx>
Principal Software Engineer, Xen Platform Team
Citrix Systems UK Ltd.  (Company #02937203, SL9 0BG)

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